<p> Energy balance components were measured over a coastal subarctic wetland in northwestern James Bay during the growing season. The Penman-Monteith combination model was used to determine surface and atmospheric controls on evaporation. The Priestley-Taylor combination model was used to calculate an evaporability parameter, a. Combining these two models resulted in determining the sensitivity of a to surface and atmospheric controls. </p> <p> Canopy, aerodynamic, and climatological resistances were influenced by onshore or offshore wind directions. Canopy resistance was dominant and showed a strong seasonal trend a averaged 0.78 and was influenced by wind direction a is most sensitive to canopy resistance, followed by vapour pressure deficit, net available energy, and aerodynamic resistance. </p> / Thesis / Bachelor of Arts (BA)

The definitive version is available at www.blackwell-synergy.com

Populations of federally-listed gopher tortoises (Gopherus polyphemus) are in decline in Mississippi. Soil and forage quality may be linked to their health and recruitment. To gain a better understanding of existing soil and forage quality conditions on areas inhabited by gopher tortoises, I investigated soil chemistry parameters, forage nutrients, and plant community characteristics from 2012 to 2013. These parameters were collected on 7 soil and habitat management treatment types in uplands on public forest lands in south Mississippi. Soil sample analyses indicated that most pH levels in soils were acidic (pH < 5.0) to strongly acidic (pH < 4.5). Greatest soil calcium levels were detected on growing season burn, moderately suitable soil areas, and soil phosphorus levels were greatest on mowed, less suitable soil areas. Greatest levels of nutrients were detected at 0 – 10 cm soil depths. Weak, positive associations were detected between soil pH and soil calcium and magnesium levels, while weak, negative associations were detected between soil pH and soil phosphorus levels. Greater levels of calcium, magnesium, and phosphorus were detected in plants collected in mowed, less suitable soil areas. Cacti, forbs and, legumes were found to have greatest nutrient levels of all the plant growth forms. Moderate, positive associations were detected between soil pH and calcium levels in legumes and vines. Weak, positive associations were detected between soil pH and forage calcium levels in forbs and native grasses. Very weak, positive associations were detected between soil pH and forage phosphorus levels in vines. I found greatest species richness and percent coverage of legumes and forbs on moderately suitable soils that received growing season fire; whereas, greater species richness and percent coverage of native grasses were detected on moderately suitable soil regardless of season of burn. Greatest percent coverage of cacti (puntia sp.) and greatest quantities of above-ground plant biomass were detected on mowed, less suitable soil areas. This information can be valuable to habitat evaluation and management for gopher tortoises.

The accuracy of the growing season used by regulators in hydric soil and wetland hydrology and the validity of ignoring land use in these definitions is questionable. This study compared measured air and soil temperature with various growing season dates and indicators, and determined the relationships between the hydrology, air and soil temperature. Water table depths, air temperature at 1-m height, soil temperature at 15-, 30-, and 50-cm depths, and CO₂ efflux were measured at 12 plots representing three landuse treatments (forest, field, and bare ground) at two restored wet flats in the thermic Great Dismal Swamp ecosystem. The forest was driest treatment. The forest air was the warmest in winter and coldest in summer, opposite of the bare ground. The forest soil at 50 cm was the warmest in winter and coolest in summer, opposite of the bare ground. Land use affected hydrology, air, and soil temperatures through the presence of surface litter and differences in shading, albedo, and ET. The regulatory frost-free period fell in between the measured frost-free period and the measured 5°C soil temperature period. Based on CO₂ efflux and soil temperature at 50 cm, the biological growing season of native plants and microbes should be year-round for forested areas, one week shorter for early-successional fields, and two weeks shorter for active cropland rather than March to November for all land uses. Changing the growing season definition of forested, thermic wet flats to year-round designation must be considered and studied carefully to avoid jeopardizing wetland hydrology qualifications. / Master of Science

The direct effects of chemically- induced reduced transpiration on soil moisture were studied in a sub -watershed of the greater Logan River drainage. No statistically significant differences occurred among the total amounts of water transpired by the treated and control units. The seasonal low points of soil moisture, in September, showed no significant differences in final moisture retention for the two years studied, either for the control or the treated portions of the study site . The 1967 season showed a lag in soil moisture depletion compared to the 1966 season. Although a later spring in 1967 may have aided in the explanation of this lag, there was good reason to believe that the antitranspirant treatment incurred a significant delay in water use. There was evidence that more effective application of chemicals might have given more positive results.

<p>Recent changes in the timing of annual events are a sign that climate change is already impacting ecosystems. Carbon sequestration by forests increases with longer growing seasons. Biodiversity can be affected by mis-timing of events through shading interactions and frost damage. Projecting forests' ability to provide these ecosystem services in the future requires an understanding of trees' phenological responses to a new climate. I begin by proposing a first order definition of an `optimal' phenological response to warming: that the mean temperature following budburst should remain essentially constant. Analogously, the temperature preceding senescence can serve the same role. </p><p>To understand which environmental cues will drive future changes in phenology, I assimilate clues from observational and experimental literature. For budburst in woody plants, spring warmth, over-winter chilling and light drive nearly all behavior, but species' responses vary widely. Species using chilling or light as safety mechanisms against budburst during mid-winter thaws are thought to be less able to phenologically track a warming climate. However, I show that even species cued solely by spring warmth are likely to under-track temperature changes. Fall cues are more idiosyncratic, and a plant's driver of senescence is likely to vary from year to year. </p><p>Models are a tempting method to untangle species budburst cues and forecast phenology under warmer climate scenarios. I tested two models' ability to recover parameters used to simulate budburst data. The simpler model was cued only by spring warmth while the complex one modulated warmth requirements with chilling exposure. For the simple model, parameters could be recovered consistently from some, but not all, regions of parameter space. The complex model's parameters were largely unrecoverable. To understand the consequences of parameter uncertainty, I applied both models to an 18 year phenological record of 13 deciduous tree species. While a few species fell into identifiable regions of the simple model's parameter space, most did not, and projected budburst dates had wide parameter-derived uncertainty intervals. These bands were wider still under a 5°C warming scenario. Even greater uncertainty resulted from the complex model.</p><p>To better understand plants' potential for growing season extension I subjected seedlings to warmer climates in a series of open-topped chambers in sites at each end of the eastern deciduous biome. Soil and air were heated to 3 or 5°C above ambient, or left unheated. For nearly all species, warming hastened budburst and germination and delayed senescence. However, these events failed to track temperature changes, happening at warmer temperatures in hotter chambers. Individual species showed a remarkable variability of all events' dates within treatments, and even within chambers. Because phenological traits are heritable, this offers a potential for evolutionary response to climate change.</p><p>This research has shown that while individual trees extend their growing seasons under warmer temperatures, they typically under-respond to the magnitude of warming, suggesting forests' capacity for increased carbon sequestration may reach a limit. However, within populations, trees vary substantially in their phenological responses, forming a possibility for evolutionarily adaptation to changing cues.</p> / Dissertation

For the past 2 years a project has been carried on by the Utah Agricultural Experiment Station and the United States Department of Agriculture, Soil Conservation Service, in cooperation with the Utah State Engineer, in the Ashley and Ferron valleys of Utah to determine the consumptive use of water in these areas. This report is the preliminary part of the third year of study. It includes a determination of unit consumptive use .. values for the major agricultural crops. These values will later be used by the Soil Conservation Service and Experiment Station in determining the valley consumptive use by the integration method. This will be compared with the valley consumptive use as determined by the inflow-outflow method

Climate changes have been observed in the Northern Hemisphere during the last century, causing a longer growing season and upslope expansion of forest, tree, and shrub limits. Here, a long-term historical perspective was used as a tool for investigating how climate change has impacted woody plants at the forest, tree, and shrub limits across the study region. For this, historical data about plant communities were used, including the position of the forest, tree, and shrub limits, gathered by the Reindeer Commission in Troms County (1914-1915). The historical data were compared to contemporary data from a re-visit study in 2022. In addition, variations in microclimatic factors were investigated by looking at the growing season length, distance to coast, slope, and aspect. Importantly, the growing season length was found to have increased across the study region with the largest increase along the coast. The increase in the growing season length led to an upslope shift in the vegetation limits, although not significantly so for the forest limit. The field layer had shifted from meadow to heath around the historical shrub limit, and non-significantly for the forest and tree limit zones, indicating that the alpine tundra is the most sensitive to the observed warming. Distance to coast and slope did not impact the shift in vegetation limits, while aspect impacted the forest limit shift. The results from this thesis indicate that future studies should expand their research beyond climate variables and explore factors such as herbivory and land use change

O cultivo do meloeiro, Cucumis melo L., desponta no estado do Tocantins como uma cultura promissora para aumentar a produção agrícola da região. Entretanto os estudos realizados ainda são escassos, principalmente no que tange ao controle fitossanitário. Os plantios realizados são baseados nos mesmos tratos culturais da melancia, Citrullus lanatus L., cultura bem estabelecida na região. Apesar disso, a planta de melão não apresenta a mesma rusticidade da melancia. Com isso o objetivo deste trabalho foi desenvolver tecnologias para aumentar a capacidade produtiva do meloeiro através da escolha dos melhores cultivares, melhor época de cultivo, tratos culturais e do manejo das principais doenças visando a diminuição do uso de fungicidas. No primeiro capítulo foram avaliadas diferentes cultivares em duas épocas de cultivo, seca e chuvosa, e a aplicação ou não de pesticidas. No segundo capítulo foram avaliadas as características de manejo da cultura, como espaçamento, adubação, controle de doenças com pesticidas e desbaste de ramos e frutos. Por fim, o terceiro capítulo analisa o controle alternativo de Didymella bryoniae (Auersw.) Rehm (anamorfo Ascochyta cucumis (Fautrey & Roum)) utilizando óleos essenciais de diferentes espécies de plantas. A maioria das cultivares analisadas apresentaram boa adaptação ao cultivo na região, em época seca, pois o cultivo em período chuvoso não foi possível devido à alta severidade do Crestamento gomoso, mesmo com a aplicação de fungicidas. A adubação mineral equilibrada juntamente com a adubação orgânica trouxeram benefícios à cultura. Os óleos essenciais surgem como uma alternativa eficaz no controle do Crestamento gomoso a fim de diminuir o uso de pesticidas. / The melon, Cucumis melo L., cultivation emerges in Tocantins state as a promising culture to increase agricultural production in the region, however studies have been performed are scarce, especially with regard to phytosanitary control. The plantations are conducted based on the same cultivation of watermelon, Citrullus lanatus L., well established culture in the region. Nevertheless, the melon plant does not have the same watermelon rusticity, with that the aim of this study was develop technologies to increase the melon productive capacity by choosing the best cultivars, better growing season, cultivation and management of the main diseases aiming to reduce the use of fungicides. In the first chapter were evaluated different cultivars in two growing seasons, dry and rainy, and the application or not of chemical pesticides. In the second chapter were evaluate the handling characteristics of culture, such as spacing, fertilization, disease control with chemicals and thinning of branches and fruits. Finally, the third chapter analyzes the alternative control of D. bryoniae using essential oils of various plant species. Most cultivars analyzed showed good adaptation to growing in the region in the dry season, for cultivation in the rainy season was not possible due thigh severity of gummy blight in all cultivars, even with the application of fungicides. The balanced mineral fertilizer with organic fertilizer brought benefits to culture. Essential oils appear as an effective alternative for controlling gummy blight order to decrease the use of chemicals.

The research presented here attempts to bridge science and policy through the quantification of climate change impacts and the analysis of a science-fed participatory process to face a sustainability challenge in the San Pedro Basin (Arizona). Paper 1 presents an assessment of a collaborative development process of a decision support system model between academia and a multi-stakeholder consortium created to solve water sustainability problems in a local watershed. This study analyzes how science-fed multi-stakeholder participatory processes lead to sustainability learning promoting resilience and adaptation. Paper 2 presents an approach to link an ensemble of global climate model outputs with a hydrological model to quantify climate change impacts in the hydrology of a basin, providing a range of uncertainty in the results. Precipitation projections for the current century from different climate models and IPCC scenarios are used to obtain recharge estimates as inputs to a groundwater model. Quantifying changes in the basin's water budget due to changes in recharge, evapotranspiration (ET) rates are assumed to depend only on groundwater levels. Picking on such assumption, Paper 3 explores the effects of a changing climate on ET. Using experimental eddy covariance data from three riparian sites, it analyzes seasonal controls on ET. An approach to quantify evapotranspiration rates and growing season length under warmer climates is proposed. Results indicate that although atmospheric demand will be greater, increasing pan and reference crop evaporation, ET rates at the studied field sites will remain unchanged due to stomatal regulation. However, the length of the growing season will increase, mainly with an earlier leaf-out and at a lesser level by a delayed growing season end. These findings - implying decreased aquifer recharge, increased riparian water use and a lesser water balance - are very relevant for water management in semi-arid regions. Paper 4, in which I am second author, explores the theory relating changes in area-average and pan evaporation. Using the same experimental data as Paper 3, it corroborates a previous theoretical relationship and discusses the validity of Bouchet's hypothesis.