Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item DROUGHT RESISTANCE IN TROPICAL TREES: TRAITS, TRADE-OFFS, AND INTER- AND INTRASPECIFIC INTERACTIONS(2020) Petprakob, Krittika; Swenson, Nathan G.; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Anthropogenic climate change is predicted to result in more frequent and severe drought in the tropics. This novel climatic condition could cause changes in tropical forest tree community structure and dynamics which will, in turn, influence their function as a climate change mitigator. Because drought-induced changes in tree communities are the outcome of the collective performance differences of individual species, understanding the causes of variation in performance among tree species in response to soil water variation will benefit our understanding of tree community responses to the future climate changes. It is the objective of this dissertation to investigate the mechanisms determining the growth and mortality of tropical tree species in response to water availability. Growth and mortality of an individual tree is the result of the interactions between the traits of an individual and its biotic and abiotic environments. In chapter 2 of this dissertation, I quantify a suite of traits in tropical tree species and examine their contributions to the interspecific variation of drought-induced mortality resistance and their distribution along a soil water availability gradient in a permanent forest dynamic plot. In chapter 3, I investigate how drought resistance traits lead to variation in growth and mortality responses among tropical tree species to water availability gradients. In the last chapter, I show that the growth and mortality of the tree species are influenced by the interactive effect of biotic and abiotic factors and drought resistance traits of individual trees mediate the strength of the effect of neighbor density on their performances along a water availability gradient. Overall, the results of this dissertation emphasize the importance of drought resistance traits in facilitating our understanding and prediction of the responses of the tropical tree communities to future climate change.Item BIOLOGICAL CONNECTIVITY OF WETLAND AND STREAM HABITATS ON THE DELMARVA PENINSULA USING AQUATIC MACROINVERTEBRATES(2019) Couch, Brock Thomas; Lamp, William O; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biological connectivity is the connection of habitats through the movement of organisms that need to utilize said habitats to maintain their life history. Macroinvertebrate communities in freshwater can create biological connectivity by dispersing between temporary and permanent water sources. For this study, I collected and analyzed seasonal and temporal macroinvertebrate data to understand macroinvertebrate communities in six Delmarva Bays and four surrounding streams and identify potential overlapping genera between habitats. Environmental data was also collected to understand seasonal and temporal similarities and differences between Delmarva Bays and streams. For environmental data, Delmarva Bays and streams were most similar during the winter sampling period and become progressively dissimilar until summer sampling periods. For macroinvertebrate data, there were seventeen overlapping taxa that were found within predator and collector-gather feeding guilds. From this data, I can conclude that there is a potential for isolated wetlands and streams to have a biological connection.