College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item GROWING STEWARDS – REIMAGINING A HISTORIC LANDSCAPE AS A VENUE FOR CLIMATE CHANGE AWARENESS THROUGH EDUCATION, ADAPTATION, AND PLAY(2023) Callahan, Erin O'Dell; Sullivan, Jack; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Historic landscapes are an important part of our collective heritage. They provide a window to the past, offering narratives of our origins and how our relationships with nature have changed over time. Such landscapes receive historic treatments, including preservation, to ensure they are suspended in their period of significance. However, this static approach is no longer effective in protecting and communicating the heritage historic landscapes were intended to share: new approaches must be considered to contend with the dynamism of both nature and culture and ensure the health of these landscapes for generations to come. As climate change is the biggest threat to such landscapes, this thesis aims to explore how climate adaptive strategies can be responsive to both the historic and contemporary context of Meridian Hill Park: a cultural landscape that has been on the National Historic Register since 1994. It will focus specifically on providing meaningful experiences for children in the landscape, as a changing climate and environment is what they will inherit.Item ESSAYS ON CLIMATE ADAPTATION AND ENVIRONMENTAL VALUATION(2022) Wang, Haoluan; Lichtenberg, Erik; Newburn, David A.; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Risk is an important component of the decision-making process. Often time, risk assessment is associated with either space or time. How agents perceive risk and how they respond to risk can have significant policy implications, especially when government programs are designed to either incentivize the provision of environmental amenities or reduce the production of environmental disamenities. This dissertation features three chapters that examine the role of risk, time, and space in evaluating environmental disamenities and amenities in the context of climate adaptation and ecosystem goods and services. The first chapter studies the spillover effects of levee building in response to rising flood risks in the U.S. Mississippi. Using newly digitized data on levee locations and elevations with the Great Mississippi Flood of 2011 as a natural experiment, I show that a 1% increase in the upstream levee elevation increased the downstream levee elevation by 0.7%. A back-of-the-envelope calculation suggests the external costs due to upstream levee building are at least $0.2 billion, reducing the net benefits of heightened levees by 55%. The results highlight the importance of regional coordination to manage large-scale natural disasters while mitigating inter-jurisdictional spillovers. The second chapter uses a discrete choice experiment implemented in a farmer survey to elicit landowners’ willingness to enroll in long-term payments for ecosystem services programs in Maryland. We address the issue of serial non-participation (SNP) when landowners always choose the status quo option and examine the role of time and risk preferences in landowners’ enrollment decisions. We find that ceiling on program participation is evident when SNP is accounted for, pointing to an inherent limitation in voluntary programs. Failing to account for SNP can also lead to quantitatively different welfare measures. Landowners are responsive to program payments with low discount rates consistent with market interest rates. Risk-averse landowners are less likely to enroll in programs, suggesting that they perceive participation to increase income risk. The third chapter proposes a novel extension of existing semi-parametric approaches to examine spatial patterns of willingness to pay (WTP) and status quo effects, including tests for global spatial autocorrelation, spatial interpolation techniques, and local hotspot analysis. We incorporate the statistical precision of WTP values into the spatial analyses using a two-step methodology and demonstrate this method using data from a stated preference survey that elicited values for improvements in water quality in the Chesapeake Bay and lakes in the surrounding watershed. Our proposed methodology offers a flexible way to identify potential spatial patterns of welfare impacts and facilitates more accurate benefit-cost and distributional analyses.Item After the Flood: Designing Land Reuse in New York's Hudson Valley(2022) Savio, Hannah L; Ellis, Christopher D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Flooding is a recurring event in the water cycle that has the potential to devastate what is in its path. Climate change is projected to make flooding worse in the Northeastern United States because of increased intensity of rainfall. An increase in the number of flooded homes where homeowners choose not to rebuild in place can be viewed as a symptom of climate change. These issues take place at the confluence of land and water, the balance of humans and our environment, and what can be learned from the past and from projections and models of the future. How can flooded sites that are not suitable for rebuilding be adaptively reused to leverage their ecological, social, and economic value? This question is assessed through a multi-scalar examination of a series of FEMA buyouts along the Kaaterskill Creek, a rural tributary to the Hudson River in New York.Item Stormwater Green Infrastructure Climate Resilience In Chesapeake Bay Urban Watersheds(2017) Giese, Emma; Pavao-Zuckerman, Mitchell A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stormwater green infrastructure (GI) practices (e.g. bioretention, green roofs) are implemented to reduce stormwater runoff and pollution in urban watersheds. However, current implementation and design is based on historic and current climate. As a result, current implementation may not be sufficient to meet runoff and water quality goals under future climate conditions. This study conducted 1) a review of previous assessments of stormwater GI climate resilience, and 2) a SWAT modeling study of two case study watersheds (one with stormwater GI and one with traditional stormwater management) in Clarksburg, Maryland. Results from both the literature review and modeling study indicate the stormwater GI can help adapt urban watersheds to climate change. Results from the modeling study indicate that stormwater GI is resilient to changes in climate, but that there may be seasonal increases in fall and winter runoff.Item Climate Change Impacts and Adaptations in Eastern US Crop Production(2017) Salazar Lahera, Natalia; Hill, Robert L; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Climate change is affecting crop production in the Eastern US and is expected to continue doing so unless adaptation measures are employed. In the first study, we conducted surveys and interviews to identify crop management practices currently used as adaptations in the Mid-Atlantic US. The results pointed to a variety of water and soil management practices, changes in crop characteristics, and changes in planting dates. In the second study, we used the Agricultural Policy/Environmental eXtender (APEX) model to evaluate future climate change impacts and adaptations in Eastern US corn-soybean rotation systems. The effects of climate change on yields ranged from decreases to increases, generally improving with latitude and worsening with time. Climate change affected corn yields more negatively or less positively than soybean yields. No-tillage and rye cover cropping did not serve as effective adaptations in regards to yields. In fact, planting rye after corn and soybeans reduced corn yields.Item Methane Emissions From A Tidal Brackish Marsh On Maryland's Eastern Shore and the Factors Impacting Them(2016) Derby, Robert Kyle; Needelman, Brian A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Methane is a potent greenhouse gas and may offset a significant portion of the carbon sequestration benefit of many brackish marshes. The objective of this study was to determine whether methane emissions varied across different hydrologic/vegetative communities within a tidal brackish marsh, and if so, what other variables varied with them. We sampled methane emissions from two brackish marshes using static flux chambers, on Maryland’s Eastern Shore. Additional data was collected from sampled marsh pore water, water level and soil temperature. We found that there was a significant difference in methane emissions between different hydrologic/vegetative communities. The results of this study help explain the factors that influence methane emissions in a tidal brackish marsh, and the vegetative communities therein; these factors could be used to develop models to better estimate methane emissions at the site-landscape level.Item Evaluation of Biochar Applications and Irrigation as Climate Change Adaptation Options for Agricultural Systems(2014) Lychuk, Taras; Hill, Robert L; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Environmental Policy Integrated Climate (EPIC) model was updated with algorithms to determine the effects of biochar applications on crop yields and selected soil properties. EPIC was validated using the results of a 4-yr field experiment performed on an Amazonian Oxisol amended with biochar. Simulations were conducted for 20-yr into the future and predicted increased values of soil cation exchange capacity, pH, soil C content, and decreased soil bulk density values after biochar applications. EPIC was then used to evaluate climate change impacts and effectiveness of annual biochar applications and irrigation as adaptation options on yields of C3 and C4 crops from representative farms in 10 Southeastern US states. Simulations were conducted for 1979- 2009 historical baseline climate data and 2038-2068 time periods using four regional climate models (RCM). Future corn (Zea mays L.) yields initially increased, but corn and soybean (Glycine max L.) yields had decreased by 2068. Future C4 crops generally produced higher yields compared to the historical yields of C4 crops. Historical baseline yields of C3 crops and future C3 crop yields were not significantly different. Biochar amendments had no effects on yields and in some cases resulted in significant yield decreases. Irrigation caused increases in corn yields, but not for soybean yields. Irrigation did result in increased C3 and C4 crop yields for some farms that were typically in drier areas. Further EPIC simulations were conducted to estimate the effects of climate change impacts and adaptations on microbial respiration, soil C content, and nitrate losses in runoff and leachate. Microbial respiration was higher under C4 crops than under C3 crops. Biochar amendments increased microbial respiration, although the relative relationship of C4>C3 microbial respiration was maintained. Nitrate losses were significantly higher in the future and followed a C3>C4 pattern. The greatest nitrate losses were observed under C3 crops with even greater losses due to irrigation. Biochar amendments resulted in reduced losses for nitrate in leachate, but not in runoff. C sequestration increased under C4 crops and biochar applications. Under some RCM weather scenarios, biochar applications and irrigation are promising adaptation strategies for agriculture in the Southeastern US.Item A Competitive Interaction and Dominance Experiment Between the Vegetative Marsh Species Phragmites australis and Spartina Cynosuroides Under Elevated Nitrogen and Salinity Levels(2013) Arthur, Michelle Lynn; Baldwin, Andrew; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In recent decades the invasive plant Phragmites australis (common reed) has spread throughout Chesapeake Bay marshes, lowering plant community biodiversity. Excess nutrient loading and salinity intrusion due to sea-level rise make these marshes vulnerable to invasions. This study examined the interaction between Phragmites australis and the native Spartina cynosuroides (big cordgrass) to determine whether dominance of one species was detected across a range of salinity and nitrogen treatments. Aboveground biomass production of P. australis was greater than S. cynosuroides at lower salinities; however, S. cynosuroides maintained biomass production as salinity increased. Fv/Fm ratios were measured as an indirect measurement of plant tissue physiological health; only Spartina maintained the ratio at higher salinities. Nitrogen addition increased Phragmites biomass and Fv/Fm ratio at higher salinities. Results suggest salinity and nitrogen interactively affect Phragmites biomass production, and that the negative effect of increased salinity on Phragmites spread can be mitigated by nitrogen runoff.Item THE EFFECTS OF FUTURE GLOBAL CHANGE ON ARBUSCULAR MYCORRHIZAL FUNGI AND SOIL CARBON: USING URBANIZATION AS A SURROGATE FOR FUTURE CONDITIONS IN FIELD STUDIES(2012) Wolf, Julie; Needelman, Brian; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Carbon, fixed photosynthetically by plants, cycles through plant, microbial biomass, soil, and atmospheric carbon pools. The effects of global change on this cycling will impact future levels of atmospheric carbon dioxide, but are poorly understood. In urban areas, temperature and carbon dioxide concentrations are often elevated to levels that simulate near-future climate changes. These elevations are not sudden, uniform step increases but are gradual and variable; as such urbanization may provide a means to simulate the effects of near-future climate changes. The dissertation research encompasses two studies utilizing urban macroclimate to study the effects of future climate change. In the first study, plots containing a common imported soil and seed bank were established at three locations along a 50 km urban-to-rural transect. In these plots, plant community development, temperature, carbon dioxide concentrations, and other factors had been monitored for five years. Subsequently, arbuscular mycorrhizal fungal structures in bulk soil were quantified. These fungi receive carbon directly from plant roots, grow into bulk soil, and can transfer immobile soil minerals to their plant hosts. In contrast to expectations, fewer fungal structures were found closer to the urban side of the transect. The second study was an observational study of soil carbon in minimally managed, long-undisturbed soils located at varying distances from urban areas. In sampling sites at 62 golf courses, similar communities of cool-season grasses had been undisturbed for at least 25 years. At each site, total and active soil carbon and many potential explanatory factors were measured and examined with multiple regression analysis. Contrary to expectations, soil carbon was positively correlated with warmer February-only mean daily minimum soil temperatures, suggesting that winter temperatures are more important than mean annual temperature for soil C storage in temperate grassland. Other correlations, including positive correlations with soil cation exchange capacity, soil lead levels, and tropospheric ozone exposure during the peak ozone season, were also detected. Potential mechanisms for the detected relationships are explored. The results of both experiments demonstrate that commonly-held expectations based on single-factor global change experiments or models are not always borne out in complex natural systems.Item Impacts of Climate Change Variables on Mosquito Competition and Population Performance(2011) Smith, Cassandra Dionne; Leisnham, Paul; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rising CO2 concentrations and the resulting shifts in hydrology can have direct and indirect impacts on organisms and communities. The system studied was aquatic container habitats, where mosquito larvae often compete for food resources. I hypothesized that elevated atmospheric CO2 concentrations (Chapter 2) and extreme precipitation regimes (Chapter 3) would alter leaf chemistry and competition between two locally competing mosquito species, Aedes albopictus and Aedes triseriatus in laboratory microcosm experiments. In Chapter 2, tannin concentration was higher in leaves grown under elevated CO2 conditions than ambient, but competition was not affected. A two-fold increase was observed in leaf biomass in the elevated CO2 chamber, and increasing leaf litter to a container system could increase toxicity to mosquito larvae. In Chapter 3, simulated drought conditions decreased leaf decay rate and increased tannin concentrations compared to continuously wet and wet-dry leaves, and amplified the competitive effects of Ae. albopictus on Ae. triseriatus.