Horticulture

The survey results also indicate that the program contributed to the alumni’s efforts by providing skills, knowledge, and confidence as well as confirming and shaping values and career goals. Blending hands-on and classroom education on a wide variety of food systems topics, combined with the Apprenticeship’s residential structure, appears to play a major role in these outcomes. THE past several years of natural resource development in the western United States have seen increased interaction between anthropologists and resident Native American groups. Nowhere has this been more evident than in California ; however, similar events have begun to unfold in Nevada in the 1980s. To date, few anthropologists operating in the development field appreciate the full extent of concems of the Nevada Indian groups, their recent gains in reasserting control over traditional resources, or even who they are. The present paper identifies the network of Indian communities spread across the state and attempts to demonstrate how many of the expressed concerns are deep-seated in Indian-white relations extending back over 150 years. Not fully considered below are cultural persistence factors involving regious beliefs, cermonial activities and many aspects of social organization , and the effects of resource conflicts on belief systems . Conflict over the control and use of natural resources in Nevada has proceeded through several levels of intensification. It began indirectly in the early 1800s when mounted Indian groups from California and the Columbia Plateau incorporated northern Nevada into alargetrade network . Ute and Navajo slaving raids were also taking place at this time at the other end of the State .

The later 1800s witnessed the statewide loss of lands and resources to mining and ranching interests and efforts to reserve some resources for use by the surviving Indian peoples. Most recently,vertical grow system the principal conflicts have been associated with the planning of massive energy systems and large-scale mhitary projects . Due to the pervasive role of the Federal govemment in the management of Nevada’s natural resources today , Indian-white relations may be frequently translated into Indian-U. S. Government relations in regard to many issues. On the other hand, because the Federal govemment does control such an overwhelming majority of Nevada’s resources, the Indian tribal governments are placed in competition against the State of Nevada for control of the balance of the resources. The following paper describes the loss in land base, the depletion of resources and the decrease of access to them experienced by the Indian peoples of Nevada and their attempts to reestablish rights to these resources . As in pre-contact time. Great Basin Indians continue to have in small groups scattered throughout the state, many on numerous Federally recognized reservations and colonies . Ties to ancestral lands have thus persisted, unbroken in time, and certain traditional practices and values are sthl key components in the maintenance of cultural integrity and social cohesion . The reservations and colonies are presently experiencing a gradual increase in growth and economic diversification. At the heart of this trend is the widespread desire for economic self-sufficiency and independence from the U. S. govemment. The form of Indiandected economic development varies to some degree, ranging from Yomba Shoshone cattle ranching to Washo industrial parks, Moapa Paiute farming and Pyramid Lake Paiute fisheries. However varied, attempts at expanding tribal lands, establishing water rights and protecting certain food resources are central to most of these efforts. These interrelated areas of contention are described in the following sections. From the 1820s to 1858, loss of natural resources and access to favored camping areas was concentrated in the immediate vicinity of two new transportation routes across northem and southern Nevada.

The traffic along these routes consisted of traders, trappers, explorers, slavers, emigrants and, in the south, Mormon colonists . By the end of the 1840s, a number of stations were established in the eastern flanks of the Sierras where emigrants could rest and graze livestock while waiting for good trans-Sierran travel conditions . Envhonmental deterioration was primarhy due to hunting and trappmg by the intruders and grazing and trampImg by theh mounts, pack animals, and livestock . By 1829, the beaver population was decimated and by 1845 emigrant diaries noted the general dechne of game and grasslands along the trahs. The loss of beaver not only took away a source of meat and clothing, but also disrupted hydrologic patterns affecting fish populations . A common response of native populations to these conditions during the first half of the 19th century was to withdraw from the routes and campsites frequented by the intruders . There were also, however, more vigorous responses, notably by elements of the Northern Paiute, who formed mounted raiding bands apparently operating out of eastern Oregon, and preying upon wagon trains in northwestern Nevada . In the south, by the early 1850s, following the long, devastating period of slave raids. Southern Paiute were becoming field laborers for Mormon colonists. A Mormon mission was established in Las Vegas Vahey in 1855 and by 1857 cooperative farming villages were located in key oases, such as the Virgin Valley. During this period many Southern Paiute were forced to abandon their horticultural fields and rely more completely on a hunting and gathering way-of-life . Many native groups in the vast south-central section of the state, yet to be directly exposed to these intrusions or to suffer the loss of land and degradation of resources, continued to follow the traditional seasonal cycle of movement . Discovery m the late 1850s of the famed Comstock Lode in western Nevada and of silver at Potosi Mountain in southern Nevada introduced a new era of more intensive resource conflict.

The most devastating effects of the northem discoveries were felt in the Washo territory , where the new town of Virginia City attracted thousands of people, and where large-scale mining soon resulted in the loss of land, and in serious conflicts over water as well as in the disappearance of game, logging of pinyon groves, and depletion of fish in the valleys. Mining led to the deterioration of streams, the spread of tailings over productive gathering areas and extensive cutting of pinyon-juniper woodlands for charcoal production, mine timbers, posts and fuel . Previously fertile seed areas were plowed to raise farm products and the important aboriginal fishery at Lake Tahoe was commercially exploited. Commercial fishing began at Tahoe in 1859 and by the 1880s, tons of trout were taken annually . Mining and associated ranching activities spread rapidly outward to other regions of Nevada in the 1860s, quickly disrupting traditional lifestyles on a much broader basis . Around Austin m the Reese River Valley of central Nevada, native grasses, reported abundant in 1859, were being heavily grazed by 1862 . Silver ore discoveries at Mt. Irish in 1865 and Pioche in 1868 led to the establishment of Panaca as a supply center for southem Nevada . Finally, the completion of the transcontinental railroad across northern Nevada in 1869 greatly expanded the markets available to Nevada ranchers, and thus encouraged the extension of large-scale livestock grazing into the “empty” lands outside the immediate vicinity of the mining communities. During this period of white expansion,cultivo frambuesa most lands claimed by ranchers under the Federal Homestead Act were choice grassy meadows watered by springs. However, since much of Nevada was unsurveyed, the homestead laws did not immediately apply and, in many areas, settlers could fence large areas and live on the land for years without holding title or any other form of legal consent by Congress . By the 1880s, huge herds grazed in northern Humboldt and Elko counties destroying native shrubs and grasses that were economically important to the Shoshone and Paiute. Major sunflower seed areas in southern Nevada were similarly eradicated . As the mining and ranching interests expanded, the Indian peoples around the state responded in large part by forming settlements on the outskirts of mining camps, railroad towns and farming communities or by attaching themselves to particular ranches . As early as 1862, there was widespread economic dislocation . The traditional seasonal economic round, disrupted in many areas by rangel and fencing , resource depletion , and the introduction of privaty property rights, was abandoned, or at best greatly modified.

Men hauled and chopped fh-ewood, sold pine nuts and fish, hauled water, dug irrigation ditches, worked as loggers, plowed fields, bounty hunted for rabbits, or commercially hunted large game, while women worked as laundresses, maids, and kitchen helpers. The production and use of most traditional technological items had essentially ceased by 1880 . The archaeological record has yielded additional information about 19th century aboriginal ties to mining towns and mral ranches . As resource conflicts intensified, so did hosthities. The mounted Northern Paiute bands raided cattle on outlymg ranches in the Pyramid Lake area . Increased depredations by miners in 1858 led to the “Paiute Indian War” which continued for several years . U. S. Army troops established posts in Ruby Valley in Western Shoshone territory in 1858 and at Ft. Churchih in western Nevada in 1860 for the protection of communication and transportation routes across Nevada . In 1863, a Steptoe Valley Shoshone vhlage was razed by troops responding to reported hostilities in the area . Similar violent clashes occurred in southern Nevada near Alamo in 1867 and again in 1875, leading to the abandonment of the Pahranagat Valley by Southern Paiute . Beginning m 1865, the state legislature of the newly formed State of Nevada passed the first in a series of resolutions asking Congress for military aid to thwart Indian “depredations” . Such was the state of Indian-white relations when the first formal attempts were made to resolve the conflicts and to protect the Native Americans from further harm. The nature of these efforts varied about the state and at different times. Many actions left important issues unresolved and they thus form the background for present-day attempt by Indian communities to obtain redress for the long string of injustices suffered by their forebears. Treaties were established with several Shoshone groups across the western United States m 1863. The Ruby Valley Treaty was signed by members of a few north central Nevada Western Shoshone groups , and the Tooele Valley Treaty by members of groups residing on the Nevada-Utah border. The purpose of the treaties was to establish friendly relations between the U. S. government and Western Shoshone, thus ensuring the safety of transportation routes, such as the new Overland Stage and Mah Route, through Shoshone territory. The treaty also allowed for certam forms of development by whites in Shoshone territory , established annual payments to the tribes for 20 years, and promised eventual establishment of reservations within the traditional territories. In subsequent years no payments were provided and the Duck Valley Reservation, not permanently established unth 1877, was located outside traditional Shoshone territory. Attempts to establish reserves in Western Shoshone territory in Ruby Valley in 1859 , the Elko vicinity in 1868 and at Carlin in 1877 proved to be false starts, causing further frustrations over lost lands. For example, a six-mile-square reservation was informahy set aside in Ruby Valley in 1859, but it was never formally withdrawn and by the 1870s it had been abandoned. A later attempt in Western Shoshone territory was initially more successful as it led to the establishment of the Carlin Reservation in 1877. A scant two years later, however, in 1879, Carhn was abolished by Executive Order due to the contesting of land claims by whites in the area . Subsequently, the Government attempted to escape its treaty obligations by encouraging Western Shoshone from as far away as the Reese River Valley in central Nevada to move to the Duck Valley Reservation. However, the great majority of Western Shoshone preferred off-reservationhfe in theh ancestral lands and refused to move . Due largely to the efforts of Indian Agent James Dodge, the Northern Paiute history of land reserves has taken a different course. Two sizable reservations—Pyramid Lake, including over 400,000 acres and Walker River, consisting of approximately 320,000 acres —were formally withdrawn in 1859 and designated as reserves in 1874. Both reserves initially included large natural lakes containing rich fish resources .

On the following days however, when exchange sites at the lower part of the stem were assumingly saturated and the amount of radio-Sr in the feed declined due to solution topping and dilution, “wash out” of radio-Sr was demonstrated by negative rates at the lower stem detectors with positive rates at the upper parts indicating continuous accumulation at the flow terminals. Each morning, a sharp increase in both transpiration and translocation rates was seen, which implies coupled transport of water and Sr ions. Within hours however, translocation rates declined although transpiration rate was relatively stable. A possible dilution effect resulting from unloading activity as well as adsorption dynamics to tissue exchange capacity could explain such phenomena. As the day advanced and transpiration rate decreased, translocation rates peaked and subsided suggesting a 2nd balance shift. The 3rd and last daily wave observed after dark can be attributed to the low night transpiration rate and a possible desorption and/or loading of Sr into the sap which needs further studies . A relative high rate daytime inflow of radio-Sr was registered at the fruit detector which contradicts with the assumed night sap filling of xylem-borne ions due to fruit expansion. A possible explanation is that the existing mature fruits having low daily volume change coupled with a high sink term result in day-fill patterns. In regard to the relative high fruit radiation rates as compared with the leaf petiole detection rates, it should be noted that fruit radiation shield geometry was different than all other shields and allowed more radiation interception at the detector as compared to that of the petiole and stem detectors.

It is likely that related normalization would reduce relative fruit radiation levels. Copper is a first-row transition metal and an essential trace mineral that plays key roles in physiological functions,vertical farming equipments such as serving as a cofactor for many enzymes involved in energy production and metabolism. However, as with many essential minerals, excessive amounts can result in toxicity. Copper is common in the environment and contamination of soil and waterways can occur from agricultural sources, where copper is found in pesticides and fertilizers, and from industrial sources, such as mining and manufacturing operations. The World Health Organization has determined the maximum acceptable level of copper in drinking water to be 2 mg/L and the Environmental Protection Agency sets the threshold at 1.3 mg/L. Due to the potential health risks of environmental copper contamination, there is great interest in methods for the analytical detection of Cu2+ ions, particularly for use in field applications. The use of colorimetric sensors offers quick and accurate naked-eye detection without the need for expensive instrumentation, such as inductively coupled plasma mass spectrometry and atomic absorption spectrometry. Several colorimetric and fluorescent sensors with structures ranging from small molecules, large macrocycles, and nanoparticle/quantum dots have been created. The strong interest in copper sensors is highlighted by a recent PubMed search for “colorimetric copper sensor”, which revealed a steady increase in the numbers of copper sensors reported from 2007-2019 . To date, most reviews on copper sensors report fluorescent sensors for copper .

However, there have been fewer reviews addressing small molecules for the colorimetric detection of copper. These reviews were narrowly focused on copper sensors that are carbohydrate-based, pyrene-based or reviewed from the years 2013-2015. Other reviews discuss colorimetric and fluorescent copper sensors in a range of sizes such as small molecules, enzymes, polymers and nanoparticles or organize by the type of optical emission produced from these copper sensors. Further reviews on colorimetric sensing of metals have broadly focused on a number of metals. This review focuses on small molecule copper sensors that offer a colorimetric response in solution, with naked eye detection, published in the years 2010-2022. We felt that researchers developing new copper sensors, or who are interested in using copper sensors, might be most concerned about sensitivity as a starting point. 102 sensors are reviewed and are organized by their reported limits of detection by absorbance or fluorescence spectroscopy. Sensors that did not report colorimetric LOD but only fluorescence LOD are organized into a separate section. Sensors that possessed naked-eye detection but did not report a LOD are included at the end of the review.Upon evaluation of the copper sensors in Table 1-12, metals such as Fe3+, Fe2+, Pb2+ , Hg2+, and Co2+ were commonly found to offer dual detection. According to the hard-soft acid base theory, metals are classified as either hard acids or soft acids . Utilizing Pearson’s absolute hardness values ranging from 3.4-45.8, where the lower the value reflects the softer metal, hardness values for these metal ions were 7.3 , 7.7 , 8.3 , 8.5 , and 13.1. Co2+ was not listed but is considered borderline, displaying intermediate characteristics.

Since Cu2+ is considered a borderline soft acid, it is reasonable to suggest interference from Fe2+, Pb2+, Hg2+, and Co2+ are due to HSAB theory. Although Fe3+ is regarded as a hard acid, it is plausible that HSAB does not apply in this case. Recognition of Fe3+ was primarily in the form of fluorescence “turn-on” detection. Interestingly, all sensors utilized a Schiff-base unit in the sensing mechanism. It is well known that various metal ions preferentially bind a Schiff-base imine due to the non-bonded electrons on nitrogen in the C=N unit. Depending on several factors such as pH, coordinating ability of the counter anions, the amine or aldehyde fragment regenerated, etc., two possible mechanisms could explain this phenomenon. Coordination of Fe3+ in the binding pocket containing a Schiff-base unit induces hydrolytic cleavage of the C=N and formation of an amine and carbonyl. This results in partial decomposition of the sensor and generation of a fluorophore enabling fluorescent enhancement. The second possible sensing mechanism involves the coordination of Fe3+ in the binding pocket containing a Schiff-base unit but instead of undergoing hydrolysis, the Fe3+-sensor complex is stabilized by the donation of the electrons from nitrogen on C=N imine. Uponemission of this complex, PET is inhibited due to the Fe3+-sensor stabilization, allowing for full relaxation of the electrons back to the ground state, resulting in fluorescence. As for Cu2+, it has been often used as a fluorescent “turn-off” sensor due to its paramagnetism. Upon emission of a Cu2+-fluorophore complex, PET is possible when an excited electron relaxes to the dx2 -y2 orbital, resulting in fluorescence quenching. Common anions that interfered with copper sensing, and offered dual detection, were S2- , CN- , and F- . Further expanding on HSAB theory, hard acids preferentially react with hard bases and analogously,vertical farm tower soft acids preferentially react with soft bases. Therefore, the HSAB theory could account for interference by sulfur and cyanide acting as soft bases. The high affinity of copper for these ligands can displace the metal from the sensor to form CuS or Cu2. Since fluoride is considered a hard base, the possible mechanism for detection of F- could be due to its electronegativity and high propensity to intermolecular hydrogen bond. Of the sensors that detected F- , this is particularly seen with hydrogens covalently bound to either an amine or phenol. The lone pair electrons on nitrogen and oxygen induce a dipole creating a partial positive charge on hydrogen, making it susceptible to intermolecular hydrogen bonding with fluoride. Overall, the ideal copper sensor used for in-field analysis would be able to detect copper only, even in the presence of competing metal ions, and be able to do so in a 100% aqueous medium, whether it be free in solution or fixed to a test strip. Even though there are 102 sensors reported in this review paper, only 60 sensors detect solely copper.

From these 60 sensors, 51 of the reports performed competition studies to rule out interference from other metal ions. 39 sensors were able to selectively detect copper exclusively, over other competing metal ions. After inspecting the number of sensors that were selective for copper detection with no interference, it is clear that there is a necessity to analyze beyond 1:1 Cu2+: Mn+ for competition studies. Only 11 sensors analyzed selectivity at higher ratios of competing metals; yet this is a very important aspect of developing an in-field sensor. Assessing the selectivity of Cu2+ with excess metal ions can reveal if the sensor renders a false positive or false negative. If so, pretreatment methods will need to be administered. Another important feature in developing an in-field sensor for detecting Cu2+ contamination in soil and water is the ability of the sensor to be applied to aqueous solutions. In this review, 9 sensors achieved solubility in 100% aqueous medium. A common workaround to adapt a sensor that was soluble in an organic or mixed-organic solvent, was to fix them to paper and make test strips. This is a practical option as long as competition studies are performed to confirm that Cu2+ selectivity remains. However, this was not fulfilled in the papers discussing paper-based copper sensors that are reviewed here. Interference studies, especially with excess competing metal ions and solubility in water, should be a priority that is addressed for future advancement of sensors being developed for copper detection. Plants adapt to their below ground environment by root morphological and metabolic plasticity. In turn, they influence soil physiochemical properties and root‐associated organisms by creating the rhizosphere, an environmental niche formed by the physical structure of roots and the release of metabolites . These complex root–environment interactions are challenging to study in general, and even more so in a manner that is reproducible across laboratories.Nutrient availability of soils, for example, can profoundly affect root morphology and provoke changes in root metabolism. Phosphate limitation typically results in elongated lateral roots and root hairs in a context‐dependent manner and in increased exudation of organic acids that solubilize phosphate . Root morphology and metabolism are further affected by microbes and microbial compounds . The presence of plant growth‐promoting bacteria can stimulate lateral root and root hair growth of Arabidopsis . Plant responses to abiotic and biotic factors are likely intertwined, as illustrated recently by a study that linked phosphate stress in plants with the structure of root‐associated microbial communities . Thus, plant phenotypes in soil are a result of a complex response to abiotic and biotic factors, and an integrated view of root morphology and metabolism is necessary to gain a holistic understanding of plant–environment interactions. Characterization of plant phenotypes in response to abiotic and biotic stresses in soil can have a profound impact on agriculture, especially as many resources, such as phosphate‐based fertilizers, are limited , and global food demand is projected to have to increase by 60% by the year 2050 due to an ever‐growing population . Grasses are central to bio-fuel production and provide 70% of human calories . Thus, research on model grasses such as Setaria viridis and Brachypodium distachyon can inform growth strategies for many crops . B. distachyon is gaining popularity as a model grass because of its small genome, short generation time, genetic tractability, and the availability of extensive germplasm and mutant collections . Additionally, sinceit uses C carbon fixation, it is a good laboratory model plant relevant to cereal crops such as barley , rice , and wheat . It has recently been utilized to investigate plant developmental processes, abiotic stresses, biotic interactions, and root morphology . The relationship between plants and their environment is ideally studied in an agriculturally relevant field setting. Environmental factors, especially the type of soil in which plants are grown, are major determinants of root‐associated microbial communities , and of root morphology . However, investigation of root morphology in soil is challenging due to its opacity, and investigation of exudation in soil is challenging due to soils physiochemical complexity . Specialized imaging techniques, such as magnetic resonance imaging, computed tomography , or the use of labeled plants , have been developed, but they are not widely accessible or amenable to high‐throughput experimentation . Similarly, approaches for the investigation of root exudation in soils include the use of in situ soil drainage systems in fields , which are low throughput and require complex installations, or of laboratory‐based extraction methods that are based on flushing the soil with large volumes of liquids .

Viral resistance using RNA homology-dependent silencing has been successfully engineered into many plant systems. Single or multiple viral-derived transgenes can be expressed in plants leading to RNA homology-dependent silencing and subsequent viral resistance. The use of this transgenic technology may be particularly effective in thwarting viral diseases where little or no genetic resistance has been identified. Resistance to rice yellow mottle virus is one example where traditional breeding cannot be used for improvement due to fertility barriers and genetic resistance being a poorly defined polygenic trait.The resultant RYMV resistant lines carried very low or non-detectable amounts of the ORF2 RNA transcript. Conversely,vertical grow towers transgenic lines that were susceptible had abundant amounts of the ORF2 transcript. Therefore the resistance phenotype was correlated with the loss of the viral transgene expression. This indicates that the mechanism of resistance was due to silencing of the ORF2 present as the transgene and in the RYMV RNA genome. The ORF2 sequence variation among different RYMV field isolates was found to be less than 10% at the nucleotide level suggesting that an RNA homology-dependent silencing approach may be effective in the field .

Viral resistance utilizing endogenous silencing mechanisms is not restricted to using a single open reading frame from one virus. Two ORF fragments from different viruses can be fused into a chimeric expression cassette to confer resistance to both viruses. One clear example was generated from using tomato spotted wilt virus and turnip mosaic virus . The open reading frame for the N gene encoding the nucleocapsid from TSWV was fused to the coat protein of TuMV and the resulting chimeric construct was used to transform tobacco. As with the example using RYMV,resistance of the transgenic plants to both viruses corresponded with the loss of transcript accumulation from both viruses as detected by northern analysis. Transgenic plants susceptible to both viruses showed accumulation of the gene fragment transcript for both viruses. These two examples have been evaluated in greenhouse experiments; however, a well-described example of RNA homology-dependent silencing for viral resistance is presently being utilized successfully in the field.One clear commercial success of generating enhanced resistance by stable expression of a viral gene is against the papaya ring spot virus . Papaya is grown throughout the tropics and subtropics and no natural resistance has been described for PRSV. A PRSV control strategy for the Hawaiian islands was developed using RNA homology-dependent silencing by expressing a mutated open reading frame for the coat protein from PRSV . Resistant transgenic plants were generated and were found to be devoid of the CP RNA indicating the RNA homology-dependent silencing of the plant-derived transgene and PRSV gene .

All PRSV strains present in Hawaii have been effectively controlled using silencing constructs derived from this mutant CP ORF. Sequence analysis demonstrated that these Hawaiian isolates had 97% or greater sequence homology to the mutant CP transgene. However, isolates of PRSV from outside of Hawaii can cause disease on the transgenic papaya lines. These geographically distinct isolates were found to have a lower sequence homology to the CP than the isolates from Hawaii. Thus, silencing of PRSV was contingent upon levels of sequence homology above 97% . Interestingly, PRSV and RYMV require different levels of homology between transgene and the endogenous gene to induce silencing. The silencing in RYMV was successful for all variations tested as compared with less than 3% divergence allowed for successful silencing in PRSV. Silencing is not only dependent upon the degree of homology but also the target sequence that is chosen. Much like the transgenic approach with R genes, each silencing construct must be carefully validated. Overall, RNA homology-dependant silencing has proven its utility in both the greenhouse and the field, and appears to be among the most versatile mechanisms currently available to engineer resistance to viruses.Crown-gall is a perennial problem in nurseries of fruit trees, nut trees and some bushy ornamental plants. Prevention of gall formation is a target for engineering resistance in these trees since breeding programs for resistance are not practical due to temporal considerations . When replanted, the trunks suffer cuts that are an entry point for the bacterium Agrobacterium tumefaciens, the causal agent of the disease, and infection becomes apparent with the formation of galls.

The bacterium causes disease by transforming the host cell with sets of oncogenes leading to uncontrolled cell division. These oncogenes encode biosynthetic genes for the production of plant hormones auxin and cytokinin. The endogenous plant genes and transferred oncogenes share no sequence homology making the bacterial genes an ideal target for RNA homology-dependent silencing . Arabidopsis and tomato plants were transformed with constructs containing direct inverted repeats of the auxin and cytokinin oncogenes . In planta, these tandem inverted repeats generate dsRNA molecules that in turn induce RNA homology-dependent silencing of the transformed Agrobacterium oncogenes. In the resulting transgenic tomato and Arabidopsis, Agrobacteriummediated transformation was not prevented but the formation of galls by oncogene expression was abrogated completely. This was confirmed by the lack of detectable RNA from the bacterial oncogenes. The transgenic plants did not show any developmental phenotypic variation indicating that endogenous hormone production was not altered by the presence of the silencing construct .Horticultural research is conducted primarily in the public sector, with research at private institutions playing a relatively minor role. As a result, research gaps naturally emerge between the basic research generated by public institutions and the research needs of industry. One approach for reducing this gap is to form public-private research partnerships that harness the complementary research and academic expertise of universities with the commercialization and marketing expertise found in industry. Such partnerships are proliferating, especially between universities and large life-sciences companies. Unfortunately, there are few concrete examples of such partnerships in agricultural biotechnology for the horticulture industry. The challenge is to adapt models of these partnerships to the research needs and structure of the horticulture industry, which produces crops such as fruits and vegetables, nuts, and nursery and ornamental crops. The traditional research paradigm posits a one-way flow from basic science conducted in public institutions to applied research and commercialization undertaken largely by private industry. This characterization does not accurately portray current trends in research and development .

Increasingly, public universities and private firms engage in joint research and establish interactive relationships. Several factors have contributed to this trend, including recent legislation , the restructuring of many of the larger life-sciences firms and an alignment of private and public incentives to pursue long-term R&D efforts . The potential benefits from university industry partnerships in the field of agricultural biotechnology are obvious. Scientific and practical knowledge can complement each other, leading to more rapid and far-reaching innovation. Universities need funding for their researchers, as well as intellectual property held by private companies and access to modern, commercially developed enabling technologies to ensure a first-rate graduate education for students. For its part, industry is interested in accessing new research and innovation, developing new products and hiring highly trained graduate students. However, obstacles to the formation of successful agreements are significant. Both parties in a research partnership face serious risks. These risks are rooted in the conflict between a university’s academic objectives and the private firm’s corporate incentives. One critical risk is the potential co-opting of the academic research agenda by private interests. University researchers risk the loss of academic freedom and integrity while industry risks the loss of investment capital,vertical growing racks privacy and proprietary information. Differences between the university’s educational objectives and corporate goals, as well as differences in the cultures, institutional incentives and time frames, can lead to a clash of cultures and values. Intellectual property rights issues are also a frequent source of contention. Given these risks, both parties need to enter into carefully structured research agreements.Most work examining research partnerships focuses either broadly, on such issues as the source of research funding, basic provisions of these agreements and associated problems and consequences , or narrowly, on specific aspects of a particular type of agreement . Although this literature is useful, it does not effectively address how to structure these public-private research partnerships. In response to this need, we have constructed templates based on the three stages of any university industry research partnerships, which provide a framework for characterizing their “front-end” and “back-end” options . University-industry research partnerships come in many forms. They may be targeted, with private firms designating specific research agendas, or they may be non-targeted. Research projects may have short or longer time horizons. Universities may enter agreements with a single private company or with groups of firms sharing a common interest . Collaborations may cover a single research project or be “megaagreements” covering a large range of interactions . Because of the inherent uncertainty in the research process, research partnerships can be structured in terms of ex ante decisions on the options embedded in the three stages of any agreement. These embedded options are specific decision points, such as determining which partner will control the research agenda.

Universities can define policies on this option ex ante, before potential partners are approached.Stage I: Setting the bargaining space. To start, potential research partners consider possible collaborations and associated trade offs. The vital aspect of this stage is determining exactly how partners will be identified and selected. Although deliberately seeking out partners rather than waiting to be approached with a proposal requires more effort upfront, it can substantially broaden the set of choices. For example, the public partner could elicit competitive bids from multiple private partners rather than just accepting or rejecting a single proposal. Stage II: Negotiating the agreement. Next, the agreement is negotiated and may or may not involve a formal contract. Front-end options determine the nature and scope of the research activities that the partnership will undertake, while back-end options determine how any benefits generated by the partnership will be distributed and how knowledge assets such as patents and commercial products are disseminated. Decisions in the front-end include specifying the research agenda, asset contributions, governance structures and scale of operations. Back-end options include designating patent filing responsibility, property and licensing rights, royalty rates and how research results will be disseminated. Stage III: Reviewing and renewing the partnership. Finally, the outcome of the partnership is assessed, with an eye toward whether to renew the agreement. Currently, there is no standard approach for formal review of large- or small-scale agreements. To assess whether a research partnership was successful or not, interested parties must rely on the informal reviews and vague impressions of both partners along with more tangible outcomes, such as the number of patents generated by the research. A key policy challenge is the development of concrete indicators or measures of productivity for public-private research partnerships.Based on these stages of forming agreements, we have designated four groups of templates. Strategic partnerships involve comprehensive, multiyear commitments between a university, or an academic department in a university, and a large company, with both partners dedicating significant assets. Formal procedures for determining research agendas and control of back-end assets are specified. Given their size, these agreements tend to come under significant scrutiny and often external review. One such agreement was the 5-year, $25 million research agreement between Novartis and UC Berkeley’s Department of Plant and Microbial Biology. The relationship, which generated approximately 20 innovations, was the subject of an internal campus review by the office of the Vice Chancellor for Research. The review found the research had not been skewed toward applied biotech research as feared and that graduate students were the primary beneficiaries.Research unit/center partnerships usually also involve the dedication of significant resources. Instead of involving existing academic departments, however, these research units are set up separately, allowing more distance between the partnership and the academic community at the university. Such partnerships may be linked to a single company, commodity group or companies that provide some or all of the financial resources for the research center. For example, the Seed Biotechnology Center at UC Davis is a partnership between the College of Agricultural and Environmental Sciences and the California seed industry.

However, recent growth strategies in this industry suggest that the private sector have leaned towards M&A-focused approaches4 rather than in-house research initiatives. The previous decade of the private sector was composed mainly of NewSpace companies developing end products and technologies for organic growth.The rise of space-focused investment funds and venture capital arms of traditional aerospace companies not only suggest private sector consolidation but incentives for being in a position to scale the R&D efforts for value creation. For example, AE Industrial Partners, a private equity group, launched a joint venture fund with HorizonX, Boeing’s venture arm. AE Industrial Partners also formed Redwire, a holding company that has acquired a number of high profile startups including Made in Space and Techshot, who both provide additive manufacturing solutions in micro-gravity, as well as companies with spacecraft and launch system capabilities.To support research development, a natural evolution toward fostering collaboration between the private and public sector could, if properly designed, provide a superior research and development platform to increase the probability of successful breakthroughs. Traditionally, NASA has largely acted as the sole public partner for most space-related public-private partnerships.

The next natural step from NASA contracting with private companies is the establishment of a public-private research and development partnerships with an expanded scope for the public dimension including the possible codification of major discoveries. PPRDPs provide a diversity of cultures of research,vertical tower planter which might be in some cases the key ingredient to breakthroughs. Government agencies traditionally follow “invented and built here” approaches, which cannot keep with the pace of innovation of the private sector. The private sector carefully tries to optimize between productivity and adherence to government standards they might not need. Universities has unique ways to use commercial products for fundamental science discoveries different from government and industry methodologies. The inclusion of universities and fundamental research institutions as additional public partners may increase the likelihood of discovering tipping-point technologies and other research discoveries. With the rise in space-related research grants and human capital development offered in university degree programs, universities could expand the public dimension of NASA to offer valuable intellectual property and more opportunities for agglomeration externalities. In this article, we first provide a historical evolution that demonstrates NASA’s shift towards a collaborative research and development process to accomplish their research agenda and mission operations in section 2. Relevant legislation and NASA funding has introduced a host of new entrants within the private sector along with funding for more active R&D programs.

In section 3, we outline public and private sector activities pertaining to major innovations that may occur within a 20-year horizon that will be instrumental in capturing the growth possibilities of the space economy. In section 4, we evaluate PPRDPs and the incentives of each partner using an emerging case study, as well as consider a novel form of governance to administer PPPs. The 1957 Sputnik crisis prompted the passage of the 1958 National Aeronautics and Space Act, which restructured the wartime-focused National Advisory Committee for Aeronautics to the National Aeronautics and Space Administration , absorbing four major research laboratories in the process. The 1958 Act also established “Space Act Agreements,” which allow NASA to contract with any entity to fulfill programs and projects. After finding considerable success in the Apollo program, the 1984 Commercial Space Launch Act recognized that the private sector was capable of developing and operating spacecraft and satellites. While regulatory guidelines and economic incentives were developed in later amendments, NASA was in a position to foster space entrepreneurship . Pressured by European post-war aspirations for technological independence from the US , leading to the emergence of Arianespace, a European launch company protected by the European Union from unlimited liability, the 1988 Commercial Space Launch Amendments Act was the first federal law to provide indemnification and financial support for commercial space companies.

The act also directed the Administrator of NASA to design a program to support research into launch systems component technologies to develop higher performance and lower costs for commercial and government launches. Following the 1998 Commercial Space Act, a critical turning point for the engagement of U.S. private industry came with the passage of the 2004 Commercial Space Launch Amendments Act. The Federal Aviation Administration ’s Office of Commercial Space Transportation issued experimental permits that allows private companies to test new types of reusable suborbital rockets. This was an initiative to allocate opportunities to other private companies other than United Launch Alliance composed of the Boeing and Lockheed Martin, which dominated the NASA private sector contracting, whose value exceeded over $12 billion . Not only were indemnification extended to 2015 but the 2004 Act created a “learning period” for commercial spaceflights, prohibiting the US Department of Transportation from issuing safety regulations beyond the informed consent regime, in which safety requirements for commercial human spaceflights were limited to informed and written consent to undertake the risk of space travel. This meant private companies could generate revenue by taking on passengers without having to deal with liability issues, allowing for the rise of space tourism companies . With the rise of newly engaged commercial space companies with technologies capable of launch and spaceflight operations, NASA fostered private entities with its Commercial Orbital Transportation Services program , which provided contracts for space companies to demonstrate cargo delivery to the International Space Station , with a possible contract option for crew transport. Otherwise, NASA would not be forced to purchase orbital transportation services on foreign spacecraft since NASA’s own Crew Exploration Vehicle would not have been ready until 2014.

With the successes of SpaceX9 and Orbital Sciences’10 cargo delivery missions, in 2012, NASA was no longer purchasing any cargo resupply services from Russia and would rely mainly on the SpaceX Dragon and Orbital Sciences’ Cygnus.The success of the COTS program allowed the 2008 Commercial Resupply Services program to contract more commercial entities to make deliveries to the ISS. The first phase of the CRS program awarded SpaceX $1.6 billion for 12 cargo flights and Northrup Grumman $1.9 billion for 8 cargo flights. The second phase of the CRS program has contracted 15 missions with SpaceX, 14 missions with Northrup Grumman, and three missions with Sierra Nevada. The most recent commercially operated space transportation program,lettuce vertical farming the 2011 Commercial Crew program, has awarded numerous companies, including Blue Origin, Boeing, Paragon Space Development Corporation, Sierra Nevada, and United Launch Alliance in its first development phase. In its second phase, Blue Origin, Sierra Nevada, SpaceX, and Boeing were awarded contracts for various enhancements to its respective spacecraft. In its third phase, NASA requested proposals to have complete, end-to-end concepts of operation, including spacecraft, launch vehicles, launch services, ground and mission operations, and recovery. Sierra Nevada’s Dream Chaser/Atlas V, SpaceX’s Dragon 2/Falcon 9 and Boeing’s CST-100 Starliner/Atlas V were awarded contracts. The Commercial Space Launch Competitiveness Act of 2015 solidified NASA’s reliance on the private sector by extended indemnification to 2025 and the learning period to 2023. The act also delegated property rights to private companies that mine resources from celestial objects , providing another incentive for private space expansion. NASA’s most recent endeavor, the 2017 Artemis Program, aims to construct the Lunar Gateway, a space station in lunar orbit. Blue Origin, Dynetics , Lockheed Martin, Northrup Grumman, and SpaceX were awarded contracts. Space venture capital activities have skyrocketed following NASA’s commercial dependency; in 2021, $17 billion were globally invested into 328 startup companies, close to doubling the previous record of $9.1 billion in 2020. In total, space-related companies have attracted over $264 billion in 1,727 unique companies since 2013 . The available evidence makes it clear that NASA has created much in the way of incentives for the private sector to actively engage in R&D, helping to solve many of the obstacles that arise in such efforts to expand the knowledge base for space exploration. A significant barrier to the full development of a space economy is the capacity to support space mobility. In the last two decades on earth, the convergence of electrification, computation, communication, control and sensing on mobile devices and vehicles has enabled the self-driving industry to emerge and the shared economy to become a reality. In a similar manner, the space economy cannot function without propulsion, launch systems and space logistics, which are all part of a new space mobility ecosystem to be created. The development of such a mobility ecosystem relies both on advances of specific technologies and new network paradigms . High barriers to entry into the space industry stemming from high transportation costs and extreme risk management currently remain. Technological advancements in the launch system industry, however, have shown great potential to scale such costs: a payload from SpaceX’s reusable Falcon 9 rocket costs approximately $2,700/kilogram, compared to a conventional nonreusable rocket and the 1981 Challenger space shuttle.

SpaceX’s Falcon Heavy rocket, in which a payload will cost ~$950/kg, is projected to save NASA an estimated $548 million for their 2024 Europa Clipper mission . Another entrant in the launch industry, Relativity Space, produces autonomous and additive manufactured reusable rockets that are projected to decrease costs even more; they have already presold more launches than any other company since SpaceX. While launch costs are already 40x lower than in 1981, some preliminary estimates price launch costs to approximately $100/kg by 2040 . Such potential to reduce barriers to entry can effectively unlock a stream for economic growth by creating more opportunities for technological innovations within the space industry’s value-added chain. Because this ecosystem is still nascent, some companies like Qosmosys are currently building ZeusX vehicles to be launched in 2026, with capabilities to mine Helium 3 on the moon for missions spanning 10 years each. There is currently no way to bring this precious cargo back, but the companies are working under the assumption that this ecosystem will exist by 2038 after the first mining mission is completed. In this nascent ecosystem, ZeusX moon spacecraft is compatible for a launch with Falcon Heavy, New Glenn, Vulcan or Ariane 64, as an illustration of the start of a logistics chain to be incrementally developed in the decades to come. While launch and other transaction costs are declining, the most efficient mode of production of goods for in-space consumption is in space production. There also exists an exigency for building an in-space manufacturing infrastructure to circumvent wait times and reducing risk for vital equipment during missions.This may have future significance in making long-distance explorations as well as long-term visits feasible . ISM requires manufacturing techniques that with more control over the drastically different environmental factors of outer space . Subsequently, novel processes have emerged to acclimate to such conditions. Companies such as Made in Space have used fused deposition modeling and injection modeling to 3D print complex parts, such as finger splints and ventilator regulator valve. Faraday Technologies and Moon Fibre produces covetic materials, or carbon nano-alloys that can be used for spacecraft and satellite components due to its efficient thermal conductivity . Within public and university research, through a grant awarded by the U.S. Department of Commerce, University of New Hampshire, in partnership with Purdue University, the University of Alabama and NASA, will focus on developing equitable industrialization of ISM by analyzing technical and commercial gaps . The greatest challenge, however, is shipping the actual 3D printing machines, the resupply of feed stock and other input resources; because such equipment consumes considerable space and weight on cargo resupply missions, the high-cost factor inhibits scalability. Tethers Unlimited also focuses on ISM with their Trusselator, but also has invented the Refabricator to reduce resupply needs by recycling plastic waste into feed stock for 3D printers. Made in Space is also attempting to bypass the “tyranny of the fairing,”in which payloads are limited in size by the nose cone of a rocket, with the invention of the Archinaut, a satellite capable of 3D-printing itself. After successful launch and orbit in space, the Archinaut will autonomously manufacture and assemble its solar panels; if successful, future payloads will not be limited by size.

Gels were made from independent root tip preparations from three different batches of plants. In-gel digestion, sample preparation, MALDI TOF and MALDI TOF-TOF peptide mass fingerprint and database searching was carried out as described in detail elsewhere. Statistical significance was tested with a t-Student test . A 2-fold change in spot signal intensity between treatments was taken as a threshold.Metabolite extraction and analysis was carried out as described previously. Root tips from eight different replicates per treatment were used. After metabolite extraction and derivatization, samples were injected randomly in split-less mode with a cold injection system and analyzed by GC using a Rtx 5Sil MS column and an integrated guard column . The GC was connected to a Leco Pegasus IV TOFMS spectrometer controlled with Leco ChromaTOF software v.2.32 . Initial peak detection and mass spectra deconvolution were performed with Leco Chroma-TOF software v.2.25. GC-MS chromatograms were processed as described previously. Further analysis after deconvolution was done using the semi-automated workflow in the UC Davis Genome Center metabolomics laboratory. Metabolite data were normalized using FW and the sum of all metabolite heights in a single run to account for small FW and GC injection variations. Statistical analysis, including i) breakdown one-way ANOVA univariate statistics , ii) multivariate analysis supervised partial least square and iii) unsupervised principal component analysis were carried out with Statistica software .

A 4-fold change in signal intensity between treatments was taken as a threshold for discussion.Crop production, especially in arid and semi-arid regions of the world where rainfall is not able to meet the evapotranspiration needs of the crops,greenhouse vertical farming depends on supplemental irrigation. Irrigated agriculture contributes 40% of the world food production from 20% of the cropped area, thus makes a major contribution to the global food security . However, irrigated agriculture may become unsustainable due to its contribution to soil degradation, salinization, waterlogging, and environmental pollution. Global water security warrants beneficial reuse of recycled water, such as irrigation, but with minimal potential harmful impacts on ecosystems. Ecosystem impairment, particularly reduced soil quality, biodiversity loss, and harm to amenity and cultural heritage values, is a growing global problem . Therefore, future irrigation schemes must address trade-offs, particularly with respect to inter-sectoral water allocations and environmental impacts. Aquatic ecosystems adjacent to irrigated agriculture are most at risk due to the transport of irrigation induced chemicals such as soluble salts, nitrates, and pesticides . The fate of these chemicals in the soils and their migration to receiving environments depend on a number of factors including the vegetation, topography, climate, soil, irrigation, groundwater level, and flow conditions in the stream . Riparian vegetation can moderate the movement of water and solutes to water bodies by interception and attenuation of chemicals moving through the buffer zone . Several investigations have examined the functions of buffer zones for stream ecosystems . However, these have mostly dealt with the overland movement of solutes via surface runoff and sediment transport.

Only, a limited number of modelling or case studies have evaluated the role played by buffer zones in reducing the migration of irrigation induced soluble salts/ contaminants via subsurface flow to streams . Subsurface flow paths can exhibit wide variations depending on specific local conditions including subsurface lithology and stratigraphy . To our knowledge, no information is currently available in the literature on the role played by buffer zones in dealing with the irrigation induced solute interception or influencing its migration to water bodies. Field experiments for assessing the role of a buffer zone on the subsurface water and salts movement from irrigated cropping system to an adjoining river is both a complex and expensive exercise. Therefore, numerical models are increasingly being used for such assessment. Hydraulic exchange across the stream-aquifer has been modelled with buffer zones or without . Similarly, Kidmose et al. employed a conceptual groundwater flow and reactive transfer model to establish a relationship between flow paths and the fate of a pesticide in a riparian wetland. Alaghmand et al. used a numerical model to evaluate the interaction between a river and a saline floodplain in relation to groundwater fluctuations, incorporating evapotranspiration losses by riparian vegetation. Klatt et al. explored the capability of a coupled hydro-biogeochemical model to evaluate the effectiveness of buffer strips to reduce nitrogen loads into aquatic systems. However, most of these modelling studies have been either conceptual and/or only partially calibrated for site specific flow and/or solute dynamics. The complicated nature of water and solute transport processes and the inherent uncertainty of input data are some of the challenges in simulating water flow and solute transport with physically based models.

Nevertheless, such models are valuable in understanding water flow and solute transport/reaction processes involved in complex bio-geological environments. This study uses a two-dimensional finite element numerical model HYDRUS to quantify the extent of water and solute exchange across a stream buffer interface. The study involves complex heterogeneous geological formations involving real-time climatic, vegetative , and stream flow conditions. The key objectives of this investigation were: i) to calibrate and validate a numerical model for water table dynamics in an area adjacent to a seasonal river by incorporating daily water level fluctuations in the river, groundwater dynamics, crop evapotranspiration, riparian zone vegetation evapotranspiration, and soil heterogeneities; ii) to estimate the impact of different buffer zone widths on the flux exchange at the river buffer interface under different cropping systems, iii) to optimize the riparian width to control the irrigation-induced solute movement to the river for different irrigated crops; and iv) to estimate the residence time of the solute tracer migrating to the adjoining water body through the subsurface under shallow water table conditions.The study was carried out at the Virginia Park gauging station at Gawler River which is situated at 12 m above the Australian Height Datum . The Gawler River only flows during the rainy season . However,vertical agriculture stagnant water /base flow conditions prevail at other times at the gauging station. The adjacent area, being a part of the vast Northern Adelaide Plains , has a relatively flat topography with a gentle slope to the west. All relevant features of the study site are shown in Fig. 1. The NAP experiences a Mediterranean climate, which is characterised by hot, dry summers and cool to cold winters. Long-term average rainfall in the region amounts to 475 mm and annual evapotranspiration amounts to 1308 mm, resulting in the irrigation demand for crop production. Water table fluctuations in the area adjacent to the river were monitored in the shallow wells . Location of these wells is shown in Fig. 1.The soils of the NAP are highly heterogeneous with depth. There is commonly a shallow clay layer at a variable depth, which determines the root growth and crops to be grown. Broader soil groups and geology of the site were obtained from the stratigraphic information of the site and well logs within the vicinity of the site. There are in general 6 major geological layers, which include red friable sandy loam soil, light brown silty topsoil, sandy clay, sandy non-calcareous clay, non-calcareous fine sandy clay, and sand. The soil particle size distributions and bulk densities of these soil groups were obtained from the previous soil analysis reported in ASRIS and the APSIM data base. The particle size and bulk density data were used to estimate soil hydraulic parameters using the ROSETTA module embedded in the HYDRUS software environment. The saturated hydraulic conductivity , and the α and n parameters were further adjusted during the calibration process and their final optimized values are presented in Table 1.must be noted that root water uptake in HYDRUS depends on the availability of water in the soil, the root spatial distribution, and differential transpiration fluxes in the crop and buffer zones. The root water uptake was assumed to be linearly distributed with depth, with the maximum at the soil surface and zero at the bottom of the rooting zone. The “trigger irrigation” option was used to generate irrigation schedules for all crops .

The trigger pressure used for wine grapes, almond, and carrot-potato, respectively, were −60, −25, and −15 kPa at a depth of 30 cm. Similar trigger pressures have been used for these crops in previous studies .The transport domain represents a 400 m cross section from the middle of the river . The vertical dimension represents the distance from the Australian Height Datum to the soil surface at the experimental site. The top width of the river was 10 m, the bottom width 4 m, and the depth 4 m at the study site. The width of the buffer zone is 30 m from the river bank. Therefore, the lateral width of the riparian zone at the Virginia Park gauging station from the middle of the river is approximately 35 m, which also includes an unsealed road which runs along the river. The finite element discretization resulted in 10,000 2D elements in a standard rectangular 2D domain. On the upper left side of the domain , the atmospheric boundary was considered through which the infiltrative influx or the evapotranspirative efflux occurs. A time-variable flux boundary condition was imposed on the upper right side of the domain to represent the buffer zone, which had different fluxes than the irrigated surface. The flux at this boundary was given by the difference between daily rainfall and daily potential evaporation . A special HYDRUS boundary condition was specified in the river. This special BC assigns the hydrostatic pressure head on the boundary below the water level in the river and a seepage face BC on the boundary above the water level. The specified water levels in the river are linearly interpolated in time in order to smooth the impact of daily fluctuations of water levels in the river . Measured values of water table depths in the well near the left boundary of the domain were used to define initial and time-variable pressure head boundary conditions. No flow was assumed as the boundary. The initial pressure head condition in the domain was specified by interpolating measured mean water table depths in the shallow wells in the adjacent area while considering hydrostatic equilibrium conditions in the vertical direction.The longitudinal dispersivity was assumed as one tenth of the modeling domain and the molecular diffusion coefficient in water equal to 1.66 cm2 /day .Measured water table depths in the shallow wells near the study site were used for the calibration and validation of the model. Simulations were carried out for 1461 days to calibrate the model for water table depths at the middle of the domain . For most sensitive model parameters including the saturated hydraulic conductivity , and the coefficients α and n of different soil layers were varied manually and no automated parameter optimization procedure was used to calibrate the model. In addition to a visual comparison of observed and simulated water table depths, a quantitative evaluation of the model performance was undertaken using goodness-of-fit measures similar to other studies . The calibrated model was validated for 1461 days by comparing the measured and simulated water table depths. The calibrated and validated model was then used to assess the impact of other irrigated crops and the buffer zone widths on the migration of water and solutes to the river. More details on different scenarios are given below in the Scenario Analysis section. To understand the movement of irrigation-induced solutes/agrochemical tracers to the river water, we considered Total Dissolved Solids as representative of all soluble solutes which is consistent with numerous studies . The initial soil conditions in the domain were assumed to be solute free. The average quantity of TDS of Class-A treated water from the Bolivar treatment plant was applied during all triggered irrigations at the atmospheric boundary where crop is being grown. However, the model calibration for solute dynamics could not be conducted due to the non-availability of site-specific data for solute transport processes.The calibrated and validated model was then used to simulate the dynamics of the hydrological fluxes and solute movement for different buffer widths and for various irrigated crops .

The CAA of 1990 acts as an insurance policy that California continue meeting the goals established in the CCAA. However, the California program will meet the federal requirements by default.Although NEPA regulates many actions, it does little to address proposed projects on a Statewide or local level. Consequently, California and thirteen other States have enacted environmental legislation to govern activities affecting their respective territories . “For most State programs, the points that must be covered in environmental impact documents are similar to those in Section 102 of NEPA” . Nevertheless, a few States include additional environmental assessment requirements . For example, California requires “an assessment of the ‘growth-inducing impact’ of proposed actions and a description of ‘mitigation measures’ that could be taken to minimize adverse impacts” .In 1970, the California legislature passed the California Environmental Quality Act , which requires that environmental analyses be performed by State and local governments before proposed actions are undertaken. CEQA recognizes several key goals for the State of California: 1) maintaining a quality, healthy environment for the future as well as the present; 2) maintaining the capacity of the environment well beyond minimal thresholds of health and safety; and 3) regulating the activities of citizens of the State to safeguard the environment,round plastic pots while preserving the lifestyles and living environment for the citizens of California §21000.

In general, CEQA’s intent is to require “all agencies of the State government which regulate activities of private individuals, corporations, and public agencies which are found to affect the quality of the environment [to] regulate such activities so that major consideration is given to preventing environmental damage, while providing a decent home and satisfying living environment for every Californian”. In comparison to other State programs, California has the broadest environmental-planning coverage . For instance, CEQA “applies to State-initiated actions, such as highway projects, as well as a variety of decisions made by cities, counties, and regional agencies. Local agency actions, which include the granting of building permits and zoning variances, have made the California impact assessment requirements applicable to proposals made by private parties. Environmental impact reports have been written for virtually thousands of private land development projects in California” . When both NEPA and CEQA are applicable to a proposed project, both regulations may be satisfied with the preparation of a joint EIS/EIR document. To help agencies fulfill the requirements of CEQA, the State Office of Planning and Research has prepared a set of CEQA guidelines.In some cases, the EIS program is managed by the State Department of natural resources. Other States rely on their environmental protection agencies .The 1990s may well be remembered as the decade in which the idea of “sustainability” first took hold in government, business, academia, and popular culture. The most well-known expression of sustainability–sustainable development–occurred at the 1992 Earth Summit, where representatives from more than 150 nations, including 117 presidents and prime ministers, pledged to integrate environmental and economic development in their respective nations’ planning and policy. Defined as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” , sustainable development has become a leading standard for measuring human progress .

In the U.S., concerns about sustainability or sustainable development have entered policy discussions at various levels of government and sectors of society. Important sustainable development projects exist at the national level , the State level , and the local level . Similar efforts to incorporate sustainability concepts are now underway in the transportation sector. For example, the Transportation Research Board completed a major study on the concept of “Transportation and a sustainable environment.” Other efforts to link transportation and sustainability include a White House sponsored dialogue on greenhouse gas emissions from personal automobiles and the Institute of Transportation Engineers’ adoption of “Transportation and Sustainable Communities” as the theme of its 1997 conference. All of these initiatives will have important impacts on the design of future transportation systems. Efforts to apply the sustainability paradigm to transportation have coincided with the advent of ITS, and a debate is now underway over whether ITS will facilitate or undermine efforts to promote sustainable communities. Replogle , for example, argues that an ITS program stressing demand management strategies could “be the most important enabling technology driver in decades to reform and progress in American transportation, winning for our citizens sustainable high wage jobs, reduced traffic delay, more livable communities, and a healthy environment.” Cervero , however, expresses far less optimism about ITS’s potential contribution to sustainable communities, arguing that a major ITS deployment program “stands to worsen by orders of magnitude” the problems of excessive auto travel, suburban sprawl, and air pollution.

We argue that ITS technologies can indeed promote efforts to build sustainable communities. By providing vast amounts of information on the performance of the transportation system, ITS could allow for greater operational control of that system and reduce the negative externalities associated with transportation. Easily disseminated information about the transportation system- -such as price signals that convey the true costs of driving, “real-time” traffic and emissions data, or information on the costs and benefits of alternative transportation policies — could enable transportation to serve the multiple economic, social, and environmental goals implied by the sustainable communities paradigm. ITS offers the prospect of a “knowledge-intensive” transportation system in which the information provided could increase mobility, reduce environmental damage, and improve the overall quality of life in communities. Such a system will not evolve automatically, however. Before the promise of ITS becomes a reality, ITS deployments must be integrated into an overarching policy and institutional framework aimed at promoting sustainable communities.Before describing possible linkages between ITS and sustainable communities, it is necessary to provide some background on the “sustainability” concept. Since the WCED’s 1987 definition of sustainable development as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs,” over 70 definitions of sustainable development have entered the policy literature . Despite its promise as a measure of progress and as a mobilizing vision, the concept of sustainable development remains controversial and difficult to define, and is particularly difficult to translate into practical action. Indeed, Ruttan correctly notes that the popularity of the WCED definition stems in part from it being “so broad that it is almost devoid of operational significance.” Take the notion of ecological sustainability with respect to a lake, for example. “Sustaining” a healthy lake as a stable aquatic ecosystem means reversing the natural process of eutrophication that slowly turns lakes into marshes, and marshes into forests. In such instances, it is ecological integrity that must be sustained,hydroponic bucket not necessarily a particular ecosystem. Despite their limitations, sustainability concepts provide useful frameworks for thinking about the future. Given that almost 200 international conferences, professional meetings, and scientific associations have used sustainability as the theme of their gatherings in recent years , it is not surprising that the transportation community is now discussing about sustainability.“Communities” represent the social and physical expression of interdependence. While they can be organized for both good and ill ends, communities connect individuals with each other, and collectively with the bio-region that envelops them. When designed to promote cooperation for mutual benefit, they provide what Robert Putnam calls “virtuous circles” or self-reinforcing stocks of “social capital: [which includes] cooperation, trust, reciprocity, civic engagement, and collective well-being.” Communities do for people what ecosystems do for nature, they bring a measure of stability and common purpose to the lives of individual organisms. Another key element of sustainable communities is concern for ecological “carrying capacity.” Ecological carrying capacity depends on at least three key factors: 1) the as similative capacity of ecosystems and bio-regions ; 2) the regenerative capacity of natural systems , and 3) the technological expansion or substitution effect, whereby man-made artifacts can be used in place of damaged natural amenities .

Physical indicators such as emission levels of CO, CO2, the level of paved surface area, etc., can suggest the threshold level for sustainability . Perhaps more than anything else, it is concerns about the earth’s carrying capacity that spur investigation into the concept of sustainable transportation.The link between ITS and sustainable transportation stems from ITS’s ability to create a transportation system rich in information, or what might be called an “information-intensive” transportation system. An “information-intensive” transportation system raises two prospects. First, it means using information instead of new lanes, roads, and highways as a way to increase the capacity of the transportation system. In this sense, ITS “substitutes information for stuff,”2 resulting in capacity enhancements that use fewer material resources, consume less open space, and reduce the noise and community disruption related to new roads. ITS thus support an underlying premise of “sustainability thinking:” that the Earth’s resource base has limits, that some of those limits are being approached, and sustainable development depends on accommodating economic growth while consuming fewer resources. Beyond potentially substituting for physical elements of the transportation system, the information provides may also enhance the system’s performance. It is critical, however, that “enhanced performance” be defined broadly to include greater traffic efficiency and a reduction in the transportation system’s negative externalities. ITS can contribute to this broader notion of enhanced performance by providing information that allows for greater operational control of the transportation system. Achieving more control of the system, in turn, increases the opportunities to address specific purposes, including broad social, economic, and environmental goals. Figure 3 illustrates ITS applications that facilitate greater control of the transportation system by channeling information to system managers and users. “Remote sensing,”for example, can generate emission data and assist air quality officials in targeting “gross polluters.” Another example is “congestion pricing,” or charging drivers a fee that varies with the level of traffic on a roadway.Congestion pricing conveys information that alerts drivers to the overall social and environmental costs of driving, making them aware that driving imposes external costs while encouraging more environmentally benign travel behavior.5Integrating transportation policy with efforts to improve mobility and accessibility, reduce air pollution, manage land use patterns, and promote social equity is an application of the sustainability framework. ITS systems, by providing information on the performance of the transportation system, provide a technological means of moving toward the sustainability ideal. But this promise cannot be realized without a transportation policy framework that goes beyond the traditional emphasis on mobility and traffic efficiency. Crucial to the creation of a sustainable transportation system is a transportation policy guided by a vision of sustainable communities. Such a vision was behind major transportation legislation passed in 1991, the Intermodal Surface Transportation Efficiency Act . ISTEA marked an evolution in the U.S. transportation policy, shifting the focus away from highway construction projects. ISTEA is the first comprehensive federal transportation legislation to explicitly endorse the idea that transportation can serve a broad range of social and environmental goals . The law instructs transportation planners to analyze “the overall social, economic, energy, and environmental effects of transportation” [CFR, 450.316]. In conjunction with the 1990 CAAA ISTEA further integrates transportation policy with efforts to control air pollution and manage land use patterns. ISTEA also mandates that the benefits of the transportation system be extended to poor and minority communities and others “traditionally under-served by the transportation system” [CFR, 450.316]. ISTEA has thus made regional transportation planning a more comprehensive, participatory process, and one in which planners are increasingly required to balance the goal of traffic efficiency with broad social and environmental concerns.This process differs significantly from traditional transportation planning, when policy makers had “few incentives to include urban renewal, social regeneration, and broader transportation objectives in their programming” . ITS provides a new set of tools to implement the holistic vision of transportation policy embodied in ISTEA, but it is critical that these tools be properly directed in relation to sustainable communities. ITS systems per se are neither all “good” or all “bad;” what matters is that they be integrated into a policy and institutional framework aimed at achieving this vision.The purpose of this part of the PATH project was to develop a methodology for evaluating the role and impact of ITS technologies on the environment.

The high base saturation under horticultural land uses as compared to < 23% for the pine forest and tea plantation soils is associated with the presence of soluble salts derived from lime, horse manure and Kfertilizer application. These soluble salts derived from the agricultural amendments are beneficial to soil fertility as they can be readily taken up by roots to meet plant nutrient requirements. Conversion of pine forest to intensive horticultural crops resulted in the increase of nitrate content by 4–7 fold . This high concentration of nitrate is explained in part by mineralization of horse manure and urea applications and the presence of positive charge on surfaces of nanocrystalline materials to retain anions. According to Auxtero et al. the positive charge of subsurface allophane-rich horizons allowed Andisols to retain mobile anions such as nitrate,hydroponic barley fodder system which is beneficial for crops. Further, the higher pH values of the IH soil may contribute to more favorable conditions for nitrification leading to the lower NH4 + and higher NO3 – concentrations found in the profile. Similar results were reported following forest timber harvest where soil NO3 – increased up to 8-fold shortly after harvest as compared to pre-harvest conditions . Previous studies measured anion exchange capacity of allophane-rich soils ranging from 0.4 to 12.2 cmolc kg−1.

This range of AEC values corresponds to 56 to 1700 mg NO3-N kg−1 , which appears sufficient to accommodate the KCl-extractable NO3 – concentrations that range up to 35 mg NO3-N kg−1 in the IH profile. Evaluation of N content in Java Island, Indonesia with different soil types and land uses showed higher soil N content in Andisols was associated with the presence of nanocrystalline materials . Retention of NO3 – within the soil profile reduces nitrate leaching and provides a readily available N supply for deeply-rooted crops . Under pine forest vegetation , the soil P retention was consistently high throughout the entire pedon . In contrast, the IH land use receiving application of horse manure for the past7 years showed appreciably lowering P retention in the upper 40 cm. The decrease in P retention and the increase of available P in the upper horizons of the IH profile were related to application of horse manure and inorganic SP36 fertilizer . These P dynamics could be associated with competition between organic functional groups derived from the horse manure and the applied P for sorption to the hydroxyl functional groups of the allophanic materials. Organic matter functional groups may block some reactive functional groups on allophanic materials, which in turn reduce P retention. In addition, the increase in pH from 4.5 in the PF soil to pH 6.1 in the topsoil of the IH soil may contribute to reduced P retention. This is supported by negative correlation coefficient between P retention and soil pH . Maximum phosphate sorption in Andisols often occurs in the pH range of 3.0–4.5 and decreases with increasing soil pH . Thus, the application of animal manure and lime appears to be an effective nutrient management strategy to enhance P availability in these high P fixing Andisols. Higher extractable S concentrations in the PF soil may be due to a combination of enhanced capture of H2S/H2SO4 emissions by the canopy of the pine forest, low S uptake by the pine forest and/or low soluble PO4 concentrations that could displace sorbed SO4. The depth trend for extractable SO4-S consisted of lower concentrations in the topsoil than the subsoil for pine forest and horticultural land uses.

This is related to competition with P and organic matter and with the increase in soil pH for horticultural crops . Previous workers have reported that sulfate and phosphate compete for the same anion-binding sites but P is adsorbed stronger than sulfate due to phosphate ions being able to form very strong inner-sphere complexes . In contrast, sulfate forms weaker inner-sphere and outersphere SO4 sorption complexes on short-range ordered materials, with the former becoming more dominant with decreasing pH and increasing sulfate concentrations . Pigna and Violante reported phosphate sorption 2–5 times greater than sulfate in Andisols and by increasing pH, phosphate sorption slightly decreased, whereas sulfate retention decreased dramatically . In addition organic matter competes more effectively with sulfate than with phosphate for sorption sites , resulting in low S availability in the topsoil horizons with high organic matter in the present study. Micro-nutrient availability is typically greater in more acidic soils due to higher metal solubility. In the present study, however, the micro-nutrient availability was higher in the horticultural soils having a higher pH . In particular, the addition of horse manure appears to provide both a source of micro-nutrients as well as high dissolved and particulate organic matter concentrations to enhance metal solubility by complexation. Therefore, manure additions appear to provide a strong benefit with respect to micro-nutrient availability for agronomic crops.The Andisols in this study contained much higher C stocks to a depth of 1 m as compared to the global average for tropical Oxisols and Ultisols of 9.7 and 8.3 kg m−2 , respectively . Further comparison to Oxisols and Ultisols from the Brazilian Amazon had C stocks from 8.5 to 10.5 kg m−2 , which were 2–3 time lower than the tropical Andisols in this study.

These comparisons indicate that Andisols have substantially higher capacity than other mineral soils to preserve organic matter. These results are consistent with those of Torn et al. who concluded that Andisols contain about twice as much organic C per m2 than Oxisols or any other soil orders, except for Histosols and Gelisols. Oxisols and Ultisols are dominated by low activity clays that provide less active mineral surfaces for physical and chemical stabilization of soil organic C . In contrast, N stocks of our tropical Andisols were similar in magnitude to Oxisols and Ultisols in the Brazilian Amazon that varied from 0.71 to 2.3 kg N m−2 , but mostly from 0.7 to 1.3 kg N m−2 in the upper 100 cm . Therefore, the Andisols of this study appeared to store organic matter with a higher C/N ratio than Amazonian Oxisols and Ultisols. Overall, soil carbon and nitrogen stocks in the upper 1 m of soil profiles increased in agricultural soils compared to the pine forest soil . These data appear to suggest degradation of soil organic C and N in the topsoil following conversion to agriculture but compensation by the elevated C and N in sub-soils. This condition results from pedon redistribution of organic C concentrations from topsoil to subsoil horizons. This redistribution may be attributed to a decrease in surface litter under agricultural land use with deeper incorporation of organic matter by tillage,livestock fodder system and/or deeper rooting system of some horticultural plants. Alternatively, the appreciably higher bulk densities of the agricultural soils contributed to higher organic C stocks compared to the pine forest soil suggesting a role for compaction in increasing C stocks on volumetric basis. Finally, it is possible that periodic volcanic ash deposits have resulted in burial of organic-rich horizons, leading to the high organic matter in subsurface horizons. Importantly, in spite of intensive agricultural production for > 100 years, there was no appreciable loss of organic matter from these soils as has been documented in many soils following conversion of forest vegetation to agricultural purposes. Similarly, Panichini et al. reported that disturbance of Andisols in Chili by forest management did not alter carbon storage. They posited that organic matter was stabilized by amorphous materials and organo-mineral complex formation, and the humid climate protected soils from irreversible drying and potential carbon loss. The ability of Andisols to strongly sequester and preserve organic C under various land-use/land management practices was demonstrated by the increase of organic matter in subsoil horizons of agricultural soils compared to the forest soil. In contrast, the lack of an organic matter build up in the topsoil and IH soil receiving horse manure for the last 7 years relative to the FH soil indicate that the added horse manure is quickly mineralized to provide nutrients to the horticultural crops. In addition, the increased N content from inorganic fertilizer may accelerate mineralization of organic C. On the other hand, the zero tillage in the FH soil contributed to the buildup and preservation of organic matter in the FH soil compared to intensive cultivation in the IH soil. The strong correlation between organic C and Alp and the lack of a significant correlation between organic C and Sio suggest that Al-organic complexes are more important than allophane in preserving organic matter in these tropical Andisols.

Microbial biomass C trends showed a positive relationship with total C and extractable DOC. The most evident change with respect to land use was the large decrease in MBC in the topsoil upon conversion from pine forest to agricultural production . Surprisingly, the lowest MBC values were found in the IH soil which received regular additions of horse manure for the past 7 years. Extractable DOC is considered an important carbon source to the microbial community and often correlates with microbial biomass. Extractable DOC represented 1.2–1.6% of total soil organic C for the PF and TP compared to < 1% for the IH and FH soils. This suggests that changes in vegetation possibly resulted in changes to the chemical nature of the organic matter affecting DOC solubility, which may affect substrate availability for the microbial community. Overall, agricultural practices had a strong impact in reducing microbial biomass C in topsoil horizons as compared to the pine forest. The microbial-labile pool of organic C is revealed by C mineralization rates during the incubation period. The overall CO2 mineralization rates followed PF > TP > IH > FH in both topsoil and subsoilhorizons . This agrees well with the highest DOC concentrations found in the PF soil and indicates more easily decomposable organic C substrates were available in PF soil than agricultural land uses. Interestingly, CO2 emissions shifted to IH > PF > TP > FH after day 70 in the topsoil, indicating depletion of easily decomposable C in the PF and TP soils. The much lower C mineralization rates in the subsoil than topsoil horizons were accounted for in part by the higher amorphous material content in the former . Chevallier et al. measured transformation of organic matter in volcanic soils by CO2 respiration and showed that the decomposition decreased as the soil allophane content increased. The low C mineralization rates for the FH profile is likely due to depletion of the microbial labile C pool as new organic carbon inputs were minimal over the last 7 years due to fallowing of the soil.This suggests that the topsoil contains more labile C substrate than subsoil horizons. According to Kavdir et al. , the fresh litter contained labile and easily decomposed materials, which mainly consisted of O-alkyl C. Inputs of new organic matter will be preferentially incorporated into the topsoil horizons and organic matter in the subsoil horizons is likely more strongly stabilized by physical and chemical mechanisms. The formation of metal–humic complexes was shown by positive linear correlation between dissolved organic C with Al- and Fe- extracted by Na-pyrophosphate . Determinant coefficients for Al and Fe were 0.84 and 0.80, respectively, suggesting that about 80% of dissolved organic C was bonded to the short-range ordered materials. The fraction of soil organic C bonded to Al and Fe varied from 25 to 50% with the magnitude following TP > FH > PF > IH in the topsoil and middle portions of the profiles . In contrast, the organic carbon bonded to metals in the lower pedon followed: IH > TP ∼ PF > FH. Previous studies on mineral control of carbon pool in Andisols in the Réunion Island showed the largest proportion of organic matter occurred as organo-mineral complexes . The lower metal-humus complexes of Andisols in the present study as compared to Andisols from Réunion Island could be associated with the higher annual rainfall and temperature under tropical conditions that accelerated organic matter decomposition. In our study the negative correlation between soil pH and Fep and Alp was observed indicating favorable conditions for organo-metal complex formation under acidic conditions .

Source and sink tissues therefore partitioned carbon into starch differently in response to abiotic stress . Source leaf showed reduced 14C partitioning into starch at MD under both mild and severe salinity and osmotic stress, and at ED under severe stress only.Since the plants were labeled 5 h after the stress treatment, the 14C flux into starch cannot provide a whole picture of starch metabolism changes during the entire stress period. It only informs on percentage change in partitioning and allocation. Therefore, absolute starch content measurements were made in source leaf and roots , to determine changes in accumulation over the time-course. Comparison of the variations in the percentage of 14C partitioned into starch with changes in starch accumulation could indicate if there are additional regulatory mechanisms leading to turnover, i.e. simultaneous synthesis and degradation. Cold, mild osmotic and salinity stress triggered enhanced starch accumulation at ED in the source. Twelve hours later , only cold and mild salinity kept starch accumulation high relative to the non-stressed control. In comparison, the 14C that partitioned into starch decreased from ED to EN , thus, the increased starch content observed might be due to inhibited starch degradation early in the day. A similar pattern was found in the roots — higher starch accumulation even though there was no change in the percentage of 14C partitioned to starch over the same period. Therefore stress may have reduced the rate of starch turnover in the roots.

Because the starch-sugar inter conversion in source leaf was acutely regulated in response to environmental cues,dutch bucket for tomatoes we further examined if changes in starch metabolism and sugar export was accompanied by the regulation of the known T6P/SnRK1 stress signaling pathway genes. Te transcript level of five selected genes in source leaf exposed to 300mM mannitol and 200mM NaCl stress, which triggered the most dynamic changes in starch metabolism, were evaluated. These genes are involved in starch synthesis, sucrose transport, and are components of the T6P/SnRK1 stress signaling pathway. AtTPS1 encodes trehalose-6-phosphate synthase, AtSnRK1.1 and AtSnRK1.1 encode two major isoforms of SnRK1, the central players of the T6P/SnRK1 pathway. AtAPL3 encodes the large subunit of ADP-glucose pyrophosphorylase that catalyzes the first committed step in starch biosynthesis. AtSWEET11 encodes a transporter that exports sucrose from leaf mesophyll cells into the phloem for transport to sinks. Our measurements showed that AtSnRK1.2 was up-regulated by osmotic and salinity stress after 6hours of treatment . However, the transcription of AtTPS1 and AtSnRK1.1 did not change. AtSWEET11 was down regulated by severe osmotic stress at the end of day. AtAPL3 was up-regulated at MD and at EN by 300mM mannitol stress, and was up-regulated from ED to EN by 200mM NaCl.Our overall aim was to develop a comprehensive map of time-dependent changes in carbon allocation and partitioning, to see how these processes were affected under different stresses. In our study, the 14C partitioning in source and different types of sinks over the diurnal cycle was examined. Under control conditions, 14C distribution into different metabolic pools in source and sink tissue, followed expectation based on previous knowledge.

Source leaf, sink leaves and roots tissues showed different carbon partitioning, with most dynamism in the source. Most carbon in source leaf flowed into storage compounds , and less flowed into structural compounds during the day. This result is similar to a previous study. Te roots also generally incorporated more carbon into RICs while sink leaves partitioned more into starch. This indicates a clear differentiation in carbon use between sink leaves and roots.Carbon allocation to the sinks was modulated by all abiotic stress conditions used in our study . Stress conditions should reduce photosynthetic capacity and carbon available for export. Knolling et al. showed that carbon export from the source to sink leaves was reduced in Arabidopsis experiencing dark-induced carbon-starvation. Our study included roots, which is a stronger sink than leaves. We found that the C-fluxes into the roots were more vulnerable to stresses than those into sink leaves . Furthermore, plants might regulate carbon allocation differently in response to long-term and short-term stresses requiring caution when making comparisons between studies. Durand et al.observed a higher percentage of 14C allocated into roots in the long-term water deficit stressed Arabidopsis. However, data from plants exposed to short-term stress in our study and plants exposed to a 16h night showed the opposite results: reduced percentage of 14C exported into roots. This underscores that timing, intensity, and type of stress regulate carbon allocation differently, even if some stresses show similar responses. Osmotic, salinity, and cold stress all triggered complex changes in carbon partitioning and shared some commonalities . All stresses increased the carbon partitioned into sugars in both source and sink tissues. They also decreased the 14C partitioning into starch in the source leaf while increasing organic acids and amino acids. Each stress had a more dramatic impact on source leaf than the sink tissues, with most changes occurring within the first 12h of stress application. Te abiotic stresses used here all triggered decreased 14C flux into RICs in the roots . Among the major metabolites pools affected, changes of carbohydrates were most consistent. Kolling et al. observed an increase of 14C into sugars and a reduction of 14C flux into the RICs pool in both source and sink leaves.

However, in our study, the increased 14C flux into sugars in the source leaf was due to the re-partitioning of 14C from storage compound , while the increase in the sink could be explained by the reduced 14C partitioning into structural compounds . Different abiotic stresses may uniquely regulate carbon use . Only cold stress caused a decrease in 14C in RICs in source leaf. Osmotic and cold stress, but not salinity stress, increased 14C flux into organic acids and amino acids in root tissues, and enhanced 14C into amino acids in sink leaves. Only cold and salinity stress, provoked changes in 14C in protein in source and sink leaves. Higher 14C in protein at the early stage of the stress progression may be due to the accumulation of stress-responsive proteins and enzymes. When stress continued, storage compound like the storage, cytosolic,blueberry grow pot and vacuolar proteins are degraded and recycled to provide energy and substrates for respiration.Te regulation of starch accumulation by abiotic stress in Arabidopsis were mainly studied during the day and only focused on leaves. Mild-to-moderate mannitol stress triggered starch accumulation, whereas higher mannitol concentrations or severe drought led to decreased leaf starch. Moderate-to-severe salinity decreased starch in Arabidopsis leaves. Cold stress induced starch accumulation in leaves in some studies, while decreased starch accumulation in others. Our study differentiated between source and sink tissues, and starch content was regulated by abiotic stress in both. There was a lack of congruency in the starch accumulation and 14C-starch partitioning under cold, mild osmotic, and salt stress in source and roots . Higher starch content in sink under stress might be due to decreased starch utilization. In the roots, more 14C accumulated as sugars because of the decreased 14C partitioning into structural compounds. In this case, it might not be necessary to degrade starch into sugars. Starch, as a sugar reservoir, regulates plant carbon balance to avoid potential famine. Maintaining sugar levels by cycles of synthesis and degradation of starch could permit metabolic flexibility with respect to starch-sugar inter conversion. Te sugars so produced may act as Reactive Oxygen Species scavengers, osmoprotectants and be an immediate source of carbon and energy to mitigate against stress. Sugar conversion to starch in leaves may prevent feedback inhibition of photosynthesis, and higher starch in the roots could help gravitational response under stress, and enhance biomass for better foraging.Transcripts levels of T6P/ SnRK1 pathway genes were regulated by abiotic stress in this study. AtSWEET11, one of the sucrose transporters, is important in whole-plant carbon allocation. It is expressed when sucrose export is high and repressed during osmotic stress in Arabidopsis leaves, when presumably export is lower. In our study, AtSWEET11 was down regulated by osmotic stress at the end of day, which suggests that the export of sugar to the sinks was inhibited. Te repression was likely due to feedback inhibition by excess sugars, this is supported by our data, which showed more 14C in sugars in the source leaf at ED, and decreased 14C imported into roots . AtAPL3 was shown to be up-regulated by 150mM NaCl stress in Arabidopsis.

Our study also observed the up-regulation of AtAPL3 by 200 mM NaCl, and 300 mM mannitol stress. Interestingly, the percentage of 14C partitioned into starch was reduced, and the end point starch content remained unchanged. Changes in the post-transcriptional regulation of AGPase rather than at the transcriptional level under stress may underscore starch contents assayed. SnRK1 has a pivotal role in regulating carbohydrate metabolism and resource partitioning under stress. In this study, AtSnRK1.2 was up-regulated by osmotic and salinity stress after 6 hours of stress treatment. However, the transcript of AtTPS1 and AtSnRK1.1 did not change, indicating a possible delayed response to stress compared with AtSnRK1.2. Te inconsistency in transcript changes of AtSnRK1.1 and AtSnRK1.2 might also be due to the specificity of these isoforms in terms of spatial expression and function. In maize, salinity stress triggered more starch and sugar accumulation in both source and sink tissues and the transcripts of the ZmTPSI.1.1 and ZmTPSII.2.1 genes in the source leaf were down-regulated, while SnRK1 target genes AKINβ was affected mainly in the sink but not in the source.The vascular system is essential for information exchange and resource allocation throughout the plant, from roots to aerial tissues. It is composed of two vascular tissue types: phloem and xylem. The phloem sap contains photo assimilates and other macromolecules that move throughout the plant from areas of synthesis or excess to areas of use and storage. The xylem sap transports water and nutrients from roots to aerial tissues, driven by a difference in water potential due to transpiration. Xylem sap can also contain a wide range of proteins involved in growth regulation, protection against environmental stress, and plant defense against pathogens. These biological processes depend on vesicular trafficking of proteins to the extracellular space, which can follow either conventional or unconventional secretion routes in plant cells. Conventional secretion requires N-terminal signal peptides or other recognition signals to direct them to the endomembrane system pathway, while proteins that follow the unconventional secretion route lack these signals. Proteins that follow unconventional secretion can allow plants to respond to a wider range of extracellular stresses and stimuli, facilitating defense responses under stress. Despite the biological importance of secreted proteins in the extracellular space to plant survival and development, proteome studies are scarce because of technological challenges. Vascular sap studies have advanced our understanding of plant responses to vascular plant diseases. The Gram-negative gammaproteobacterium Xylella fastidiosais a xylem-limited pathogen that colonizes several economically important crops worldwide causing diseases such as Pierce’s disease in grapevines, citrus variegated chlorosis, and most recently olive quick decline syndrome in Europe. Because of its significant economic impact on citrus production in Brazil, Xf was the first plant pathogen to have its genome sequence determined. The genomic landscape provided an initial description of potential virulence factors and revealed the absence of a type III secretion system commonly employed by plant pathogens to deliver virulence effectors inside plant cells. Subsequent molecular and cellular studies proposed that the mechanism of disease symptoms would be associated with biofilm formation and xylem blockage triggering the observed disease symptoms. Additionally, genomics and proteomics showed the importance of virulence factors secreted by the type II secretion system and outer membrane vesicles for symptom development. These studies highlighted the molecular complexity of the plant-pathogen interaction that takes place in the vascular system. The importance of proteins in the plant response to Xf was detailed in several proteome studies comparing infected and uninfected grapevine stems and the infection responses of different cultivars. These studies identified more than 200 proteins associated with disease resistance, energy metabolism, protein processing and degradation, biosynthesis, stress-related functions, cell wall biogenesis, signal transduction, and ROS detoxification among others.

However, the number of invasive plants with horticultural origin is high, making it critically important to natural resource managers, ecologists and policymakers to predict which newly introduced species pose the greatest risk of escape and invasion.California has approximately 3,400 species of native plants, of which 24% are found only in the state . However, California is also some thing of a hotspot for nonnative plants, with over 1,500 nonnative species naturalized, weedy in agricultural systems or invasive in natural areas . As a result, California not only faces a high risk of escape, establishment and invasion of introduced ornamental plants, but also has a high proportion of native species threatened by invasive plants. Within California, there are two lists that identify invasive plants. First, based on 13 questions that assess impacts, invasiveness and distribution, the California Invasive Plant Council’s list includes 214 species that cause ecological harm in the state’s wildlands . Approximately 63% of these species were deliberately introduced to California, mostly as ornamental plants . Second, the California Department of Food and Agriculture Noxious Weed List primarily lists plants that cause, or have the potential to cause, economic damage to the state’s agricultural industry; CDFA has legal authority to regulate plants on this list through Section 4500 of the California Code of Regulations .

Because the criteria for these lists have a different focus,gutter berries the listed species overlap but are not the same. Few species derived from the horticultural trade are included on the state Noxious Weed List. The horticultural trade is one of the major pathways for invasive plants in California and elsewhere . For example, higher market frequency and lower prices were shown to be good predictors of a plant’s probability of invasion in Britain . Horticulture is also a major agricultural sector in California, accounting for $2.5 billion in sales in 2011 . The ability to predict potential invasiveness is important both for species that have already been introduced to a region but are not yet invasive and for species that may be introduced through the horticultural industry in the future. In both cases, prediction of invasiveness before it occurs can, through collaborative efforts with the nursery industry, lead to voluntary restrictions in sales, preventing the potential for damage should the species escape cultivation. Knowing that a plant is invasive in one region can give insight into whether it might be problematic in another region, particularly if the two regions have similar climates. For woody or namental species, for example, being invasive elsewhere was the single best predictor of potential invasiveness in a new region of introduction . In addition, Caley and Kuhnert showed that four variables were most important for screening potential invasive plants: human dispersal, naturalized elsewhere, invasiveness elsewhere and a high degree of domestication.

Two of these variables, human dispersal and high degree of domestication, are characteristics of horticultural species. California is one of five Mediterranean climate regions in the world, along with the Mediterranean Basin of Europe and northern Africa, central Chile, the Cape Region of South Africa and western Australia. All these regions are characterized by a winter rainy season and a summer dry season and are likely to share invasive species due to their similar climates. The primary objective of this study was to identify ornamental species at high risk of becoming newly invasive in California. To develop this list, we considered the single most important factor to be a species’ invasiveness in other areas of the world with a similar Mediterranean climate or in a state neigh boring California. While we recognize that this list is not comprehensive, we believe that it provides a good starting point for subsequently conducting risk assessments that could reduce the threat of introducing new invasive ornamentals to the state. This approach might also help determine which naturalized species should be monitored to see if they will become truly invasive. Invasive plant data were collected through online databases and published lists from other regions with Mediterranean climates. We also used established invasive plants reported from states neighboring California, including Arizona , Nevada and Oregon . We included spe cies on the California Noxious Weed List as well as those that have been shown to invade wildlands . Of the plants that have invaded other Mediterranean regions, we first removed species native to California and those already known to be invasive in wildland areas within the state.

Then for each of the remaining plant species, we evaluated the Mediterranean-type region invaded, location of origin, human uses and whether the species was native, cultivated, naturalized or invasive in California . For species already naturalized but not yet invasive in California, we determined the year they were first re ported as naturalized based on the online Consortium of California Herbaria data base . In addition, we determined if plants are currently sold in the horticultural and ornamental trade in California using the Sunset Western Garden Book and the Plant Locator , a directory of nurseries stocking particular species. While these references do not include all of the species available by mail order or via the Internet, they represent plants most commonly available in nurseries.Based on our criteria, we found 774 plants listed as invasive in other Mediterranean regions or adjacent states . Of these, 366 are not natural ized in California and therefore fit our focus on potential new invaders. Of the remaining 408 species , we eliminated 318 species that did not fit our focus on new invaders: they were either native to California or al ready invasive in California , or had naturalized in the state before 1940 without becoming invasive . This left us with 90 species that naturalized after 1940. We assumed that species that naturalized before 1940 and that have not yet be come invasive in California are unlikely to become invasive in the future. Many of the naturalized species have been present in the state for over a century, with 20 recorded in the 1860s and 144 recorded before 1900. While we believe that 70 years of naturalization without significant spread and harm is sufficient to consider a species as having low potential for invasion, this may not be true for all species. There may be some instances where longer lag periods — a length of time when a species is present in natural areas before beginning to spread and cause ecological harm — could occur prior to rapid expansion of a species. Furthermore, the movement of ornamental plants is facilitated by humans, thus increasing the opportunity for introduction to suitable habitats. In addition to possibly increasing the potential for invasion by introduced plants,strawberry gutter system this facilitation could also reduce the time between introduction and invasion. Next, we subdivided the 90 species that became naturalized after 1940 and the 366 species that are not naturalized in California based on whether they are sold as ornamentals. We also noted whether they are sold in California . Of the 90 naturalized species, 70 are currently sold as ornamentals some where in the world, with 60 sold in California. Of the 366 non-naturalized species in California, only 32% were ornamentals.

The majority of these species are currently sold in California, while the other 22 are ornamentals not sold in the state. Thus, in total, we listed 186 species of ornamentals as the greatest concern for introduction and/or invasiveness to California through the horticultural pathway. This total includes both those species currently sold and those that could be sold in the future . This study, however, did not take into consideration the potential effects of climate change on habitat suitability and plant invasions within California. It is possible that warmer temperatures or modified precipitation patterns due to climate change will allow some currently noninvasive ornamentals to spread and become invasive. However, predictions of the spread of invasive plants in the western United States indicate that while some will likely spread, others may contract their ranges . Thus, it was not possible to determine the impact of climate change on all the species evaluated in this study.To reduce the sale of invasive plants in California, environmental groups, scientists, government agencies and the horticulture industry are participating in the Plant Right partnership, a coalition that works with retail nurseries and grow ers on voluntary measures to reduce the sale of invasive plants and promote non invasive alternatives ; the authors serve on its steering committee. Specific guidelines or recommendations could be established for the high-risk species we identified in tables 1 to 4 to minimize future introduction, establishment and invasion. Cooperative efforts can discourage the introduction of ornamental plants in other regions that are neither naturalized nor sold in California , and these plants also could be included in a cautionary list that would require full prescreening risk assessment before introduction to the state. Plants that are not naturalized in California but that are sold here should be reviewed by the nursery industry to reduce their sale and also watched for any spread into wild lands. In addition, noninvasive ornamentals that serve the same purpose in a landscape should be promoted as alter native options. Species that are naturalized but not yet sold in California should be restricted from sale, and land managers should watch for their further spread. Finally, species that are both naturalized and also sold in California may be considered for removal from the trade and also watched by land managers for further spread into wild lands. This list provides a good starting point for identifying plants, especially ornamental species, that are invasive in regions with similar climates to California and could become problematic here. However, additional steps are required to further understand the potential risk of invasion. In particular, a more detailed risk assessment should be conducted for each of the species we identified as being at high risk for future invasion. Several risk assessment protocols are available to prioritize the greatest potential threats to wild land systems. Implementing these preventative approaches and establishing an early detection program to eradicate incipient populations of these targeted species are far less costly than attempting to manage or contain large well-established populations of invasive plants. The use of copper-based nanoparticles in agriculture as fungicides and bactericides is increasing rapidly due to their relatively low toxicity and higher efficiency in delivering the active component . There are numerous copper containing pesticides on the market, e.g. copper sulfate , cuprous oxide , copper hydrox ide , and nano copper . The U.S. Department of Agriculture maintains an official list of synthetic substances that can be used for organic farming. According to this list, copper-based materials are allowed for use in organic crop production.However, more and more evidence indicates that copper-based nanoparticles induce phytotoxicity in various plants, such as bean,lettuce,alfalfa,cilantro,cucumber.The adverse impact in clude decreased root and shoot elongation, disturbed mineral nutrients homeostasis, decreased photosynthesis rate, inhibited antioxidant enzyme activities.So far the molecular mechanism underlying those physiological changes is not well understood. In recently years, “omics” have become a promising meth odology for studying plant responses to abiotic and biotic stress.Transcriptomics-based gene expression and proteomics-based protein production have been applied to evaluate the changes of plants to external stressors at the mo lecular level.Unlike transcriptomics and proteomics, which reveal what might be happening in plant tissues, meta bolomics profiling can tell what already happened. Metabo lites are the end product of gene expression,16 and the changes of metabolites are regarded as ultimate responses of plant to stress. Thus, environmental metabolomics is be coming a powerful tool to investigate the response of plants to various stressors, e.g., water, light, temperature, and high levels of metals.18 Recently, Pidatala et al. employed LC-MS/ MS based metabolomics to elucidate the stress response mechanism of lettuce to lead. They observed several key metabolic pathways, including sugar and amino acid metabolism, that were disturbed by lead.Our recent study,apply ing GC-TOF-MS based metabolomics and PLS-DA multivariate analysis, also revealed the profile of metabolites in root exudates was significantly altered by nCu. A number of amino acids were up-regulated to defend against an excess of copper. More recently, we determined that nCu altered the nutritional supply of cucumber fruit,21 using 1 H NMR and GC-MS based metabolomics.

Recently, a number of studies suggested that increased SSTs in the STIO may cause large-scale changes in atmospheric circulation and divert important moisture transports away from the GHA, altering previous relationships between regional circulation and precipitation . In an analysis of boreal spring , Williams and Funk found that higher SSTs in the STIO have driven large increases in convection and precipitation over the STIO. The resulting increase in the amount of diabatic energy released during precipitation has led to increased diver gence of dry static energy in the mid- and upper troposphere. During MAMJ, this intensified outflow of mid- and upper-tropospheric DSE from the STIO has increased subsidence over northern Africa and decreased moisture transport into the GHA for at least the past 30 years. The decrease in the amount of moisture trans ported into the GHA region appears to have caused a reduction in what MAMJ precipitation totals would have otherwise been in the absence of increased SSTs in the STIO. Therefore, increased SSTs in the STIO and subsequent changes in moisture transports may signify a long-term alteration in how interannual variability in atmospheric circulation impacts interannual variability in precipitation totals throughout much of the GHA. While no existing data sources detail the true sources of GHA precipitation,hydroponic grow table the composition of stable isotopes in Ethiopian rainwater suggests that most of the moisture is derived from the rainforests of the Congo Basin.

Rain water molecules in the Ethiopian Highlands and sur rounding areas have exceptionally high levels of the heavy stable isotope of oxygen . The high level of 18O relative to 16O is evidence that the Congo Basin is a primary source of moisture to the GHA because moisture transpired by the wet forests of the Congo Basin does not undergo isotopic fractionation . Unfortunately, isotopic records of precipitation throughout the GHA are inadequate to determine whether there is a trend in the proportion of precipitation coming from the humid continental interior. Conveniently, trees use rainwater to create cellulose during photosyn thesis, and d18O in precipitation is partially conserved in cellulose . In trees that produce annual growth rings, the isotopic composition of cellulose in tree rings may reflect an annual record of d18O in precipitation . We will investigate whether this is the case for trees in the Ethiopian Highlands. In this study we use a unique network of over 1,200 publicly and privately available gauge records from northern and eastern Africa to calculate a best-estimate record of JJAS precipitation for the GHA through 2009. Where sufficient precipitation data are available, we quantify the degree to which the GHA has recovered rel ative to the 1970–1989 mean. We then identify the atmospheric mechanisms that governed interannual variability in GHA precipitation during the period of 1948–1989 and determine whether the relationships between GHA precipitation and these mechanisms remained stable from 1990 to 2009. We utilize reanalysis climate data and a tree ring isotope record from the Ethiopian Highlands to test the possibility that rapidly rising SSTs in the Indian Ocean have acted to suppress JJAS precipitation in the GHA following the peak of the Sahel drought in the 1980s.

As the primary basis for evaluating precipitation trends throughout the Sahel and GHA, we use 0.25 spatial inter polation of a dense set of observational gauge precipitation records . This dataset was developed by the Climate Hazards Group at the University of California, Santa Barbara. The gridded product was constructed using qual ity-controlled rain-gauge data from 109 stations in Sudan, 210 stations in Ethiopia, 57 stations in Uganda, 144 stations in Kenya, and 817 stations throughout other Sahel and east African countries. Because the CHG is an active member of the Famine Early Warning Systems Network and routinely obtains and analyzes up-to-date meteorolog ical records to support decision-making processes for food security, the CHG archive has substantially more recent observations than those found in standard global station archives. Figure 1 shows maps of mean gridded JJAS precipitation totals, gridded mean standard-error estimates, station locations, each station’s percent of reported monthly JJAS data from 1948 to 2009, and a plot of the number of reporting stations in the Greater Horn region during each JJAS season. The CHG-CLIM dataset and underlying methodologies are described in detail in Funk et al. and summarized in the ‘‘Appendix’’.We limit our region of focus to areas within Sudan, Ethi opia, Uganda, and Kenya where the following criteria are met: mean JJAS precipitation during 1990–2009 is less than that of 1970–1989, mean JJAS precipitation exceeds 75% of mean MAMJ precipitation, which is the dominant rainy season immediately south of our region of interest, and mean JJAS precipitation exceeds 150 mm. The study area includes southern Sudan, western Ethiopia, northern Uganda, and parts of western Kenya. While the term ‘‘GHA’’ is generally used to refer to a quite larger region, we use the term to refer only to our study area defined here. Our GHA region is outlined in red in all map figures beginning with Fig. 2. To calculate a time series of JJAS precipitation for the GHA, we first standardized each grid cell’s time series by subtracting its mean and dividing by its standard deviation.

We then calculated the region’s average standardized anomaly from each JJAS season during 1948–2009. The resulting time series of mean seasonal anomalies for the region accounts for 59% of the interseasonal variability throughout the region. This meanprecipitation time series is most representative of precipitation in the central portion of the GHA and less representative toward the boundaries . Similar to what has already been established by several studies focusing on the Sahel ,flood tray precipitation varies fairly ubiquitously across the GHA as a whole . Superimposed upon this regional mode of variability is a dipole-like pattern that causes the north and south to experience anomalies of opposite sign . We explore sub regional variability later in the drought-diagnostics portion of this paper. It is crucial to this study that the CHG-CLIM data accurately reflect the direction of precipitation trends in the GHA following the Sahel precipitation decline that ended in the 1980s. Gaps in publicly available data and the cost of privately held data from eastern Africa, especially from Ethiopia, have caused previous studies to exclude parts of the GHA . A recent study that employed data purchased from the Ethiopian Meteorological Agency found good agreement with global gridded precipitation estimates for boreal summer months. The authors concluded that the purchased dataset is more accurate for Ethiopia than the global products, although they did not compare multi decade trends among the various products . The Ethiopian station data used in our study were also purchased from the Ethiopian Meteorological Agency, and are similar in quality and quantity to those examined by Dinku et al. . Given a shortage of literature on JJAS precipitation trends in the GHA following the Sahel drought, we com pared our calculations of post-drought trends in the GHA to those of 10 alternate global precipitation products . We used CHG-CLIM and each of the 10 alternate products to compare the direction and rate of change in JJAS precipitation in the GHA during the 1970–1989 period to that of the 1990–2009 period. For a wider regional perspective, we repeated this procedure for the Sahel region to the west . We also evaluated precipitation trends in the GHA and Sahel from 1998 to 2009 using the satellite-derived Tropical Rainfall Measurement Mission 3B43 merged product . While TRMM 3B43 covers a shorter time period than the other data sets used here, it is useful for evaluating precipitation trends over the last decade because the amount of missing gauge data over the GHA increases during the same period.The sub-regional precipitation records accounted for 75% of variability in the north and 68% in the south. In order to evaluate Indian Monsoon-GHA precipitation relationships we compared JJAS Bombay SLP to the north and south sub-regional CHG CLIM precipitation time series using monthly station SLP data from the Global Historical Climate Network . If Bombay SLP did not adequately represent a regional precipitation record, we considered monthly SLP data from 1,107 alternate stations in Africa, southern Eurasia, and the Maritime Continent . We calculated the correlation between precipitation and SLP at every pair of stations from 1953 to 1988. We identified the pair of regions where SLP records could either be summed or subtracted to most accurately estimate JJAS precipitation. We used three different reanalysis data sets to analyze how sub-regional precipitation variability is related to large-scale atmospheric circulation and vapor transports.

For the period 1948–1988 we used the NCEP/NCAR and ECMWF ERA-40 reanalysis climate datasets. To test whether relationships established with SLP during 1948–1988 were stationary after the peak of the Sahel drought in 1988, we analyzed trends in both the original NCEP/NCAR reanalysis and NCEP-DOE Reanalysis 2 data . NCEP2 uses an updated forecast model and data-assimilation system from the NCEP/NCAR reanalysis and it includes satellite data. We visualized trends in, and correlations with, wind-vector data using quiver-plot maps. In these maps, the x-axis of an arrow refers to the zonal wind component and the y-axis refers to the meridional wind component. In vertical profile maps depicting trends in, or correlations with, both horizontal and vertical wind velocity along a horizontal transect, the x-axis refers to the horizontal velocity component parallel to the transect and the y-axis refers to the vertical velocity component. Informed by previous research , we investigated whether trends in Indian Ocean SSTs have impacted atmospheric circulation and moisture transports in ways that would influence GHA precipitation. We focused on the STIO region, defined here as 15 S–0 S, 55 E–90 E. We evaluated correlations between average JJAS SST in the STIO and spatial fields of four variables: total cloud cover , net upward surface energy flux , dry static energy , and precipitation . We calculated energy fluxes using definitions provided by Trenberth and Stepaniak . Net surface energy flux comprises the net upward radiation flux from the ocean’s surface plus the upward fluxes of sensible and latent heat from the ocean’s surface. DSE is the sum of the energy contained in the temperature and geopotential height of an air column. We evaluated how higher SSTs in the STIO during recent decades have impacted interannual relationships between SLP and JJAS precipitation in the GHA. For each of the two GHA sub-regions, we classified JJAS seasons from 1948 to 2009 based upon whether SLP conditions were favorable for precipitation , and whether SSTs in the STIO were warm or cool. We designated all seasons with neutral SLP or SST conditions to a fifth ‘‘neutral’’ class. We evaluated mean JJAS precipitation in the GHA during each of the five classes of seasons.At the compound of the Debrebirkan Selassie church in Gondar, Northwest Ethiopia , 5 mm diameter cores were obtained from Juniperus procera trees in May 2007 as part of a larger sampling campaign . Successful cross-dating between 32 trees from five sites in the North Gondar zone was achieved by comparison of the wood anatomy directly on the surface of the samples and skeleton plotting . Cross-dating was evaluated using the computer program COFECHA and the annual nature of the tree rings was confirmed by AMS radiocarbon dating . Oxygen isotope ratios were measured on one tree core in a pilot study to obtain a preliminary insight into the potential environmental sensitivity of this isotopic variable in tree rings. Slivers were cut from absolutely dated annual growth rings representing years 1905–2003. Lignin was oxidized by the in situ generation of chlorine dioxide and hemicelluloses were hydrolyzed from the resulting holocellulose to yield a-cellulose . After sample homogenization, 0.30–0.35 mg of dry a-cellulose was weighted into silver vessels and pyrolysed over glassy carbon at 1,090C. Oxygen isotope ratios were measured using a PDZ Europe 20-20 mass spectrometer interfaced to a Europa ANCA GSL elemental analyzer at Swansea University . Oxygen isotope ratios are expressed as permille deviations relative to the VSMOW standard . Analytical precision was typically 0.3% as was illustrated by a repeat analysis of samples from 1910 . Two influential variables on tree-ring d18O are the d18O of precipitation and the amount of isotopic enrichment of leaf water that occurs during transpiration .