Browsing by Subject "Landscape ecology"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Biogeography of upland bird communities in the Peruvian Amazon(2009-12) Pomara, Lazarus Yates; Young, Kenneth R.; Barth, Robert H.; Dull, Robert A.; Miller, Jennifer A.; Ruokolainen, KalleThe western Amazon is known to be one of the most biologically diverse regions in the world, yet information about the spatial distribution of that biodiversity and the processes governing its distribution remains scarce. An improved understanding of those biogeographic patterns and processes can inform conservation and development planning in areas where anthropogenic landscape change is ongoing. Spatial components of biodiversity are known to be influenced by historical and present-day physical and human geographic processes. There is evidence that major Amazonian rivers form the boundaries of biological regions, at least for birds. Other factors that may influence bird species composition include the dispersal limitations of individual species, forest plant species composition and structure, topography, forest fragmentation, and hunting. Sites where bird species composition was measured in this study represented mature, upland forest on both sides of the Amazon River, and a range of non-flooded forest types, as indicated by soil and plant surveys. Bird species compositional variation was closely correlated with variation in plant species composition, human disturbance associated with forest fragmentation, and position north or south of the Amazon River. The strongest differences were between opposite sides of the river, even though local environments, including plant composition, were not different on the two sides. This strongly suggests that historical biogeographic factors, rather than present-day environmental gradients, are responsible for bioregional boundaries at Amazonian rivers. The difference between plant and bird distributions at this scale underscores the pressing need to re-evaluate general notions of bioregional complexity and pattern in the Amazon basin. Locally, the influence of habitat fragmentation on animal communities, including reduced species richness, was confirmed. The influence of local floristic variation is of particular importance due to its ubiquity across western Amazonia. Thus, understanding the distributions of soils and vegetation is critical for explaining Amazonian animal diversity. The use of these factors to model bird community heterogeneity contradicts assumptions that the processes shaping Amazonian animal community diversity are too complex to measure efficiently, and their use contributes a new understanding of the dimensions of that diversity.Item Connecting backyard wildlife habitats in Austin, TX : case study of Wildlife Austin(2009-12) Koone, Emily Anna; Dooling, SarahUrbanization is considered one of the leading threats to biodiversity and wildlife habitat (McKinney 2002; Shochat et al. 2006). Urban environments are humandominated systems, yet they support wildlife habitat and provide meaningful ecological functions. Methods to conserve biodiversity and minimize habitat loss and fragmentation in urban environments include utilizing private residential yards and gardens to enhance habitat connectivity. Private residential yards or gardens designed to attract and support wildlife are known as backyard habitats and wildlife gardens. The City of Austin, Texas initiated Wildlife Austin in 2007. Wildlife Austin coordinates backyard habitats in Austin as a National Wildlife Federation Community Wildlife Habitat [trademark]. My research analyzes the goals of the Wildlife Austin from the perspective of landscape ecology and urban ecology; reviews research related to backyard habitats in order to identify ways of enhancing habitat connectivity for bird communities; and provides recommendations for a more scientifically grounded approach and management in the promotion of backyard wildlife habitat.Item Ectoparasitic assemblages of Paraguayan bats: ecological and evolutionary parspectives(Texas Tech University, 2004-12) Presley, StevenNot availableItem Exploring the effects of local development regulations on ecological landscape structure(Texas A&M University, 2005-08-29) Kim, Jin KiAn ecological approach to land-use planning is essential to maintain the long-term sustainability of ecosystem benefits, services, and resources. Concern about environmental quality and the long-term livability of urban areas is now a driving force in urban planning and design. The interrelated issues of growth management, smart growth, sustainable development, and new urbanism are topics in the most vibrant discussions at all levels of planning and landscape architecture. Within this context, this study starts from the interest in the ecological planning and management in urban areas, especially related to the issue of local development regulation and guidelines. Landscape regulations have come into existence recently in communities across the nation and these regulations vary from one region to another and from one community to another. The aims of this study were to investigate the relationship between ecological landscape structure and local development regulations over time. Comparison analysis was conducted between two areas that had similar pre-development ecological conditions but were developed under vastly different regulatory environments. The Woodlands (regulated to protect ecological condition) and the North Houston area (which followed traditional subdivision regulations) were examined at three different developmental time periods: predevelopment, early development (after 10 years), and matured development (after 30 years). Aerial photos of each site from the three time periods were classified into forested and non-forested classes and the landscape structure was quantified with a number of landscape metrics related to fragmentation??an indicator of habitat degradation. Two factors, the ecological approach to landscape planning and the adoption of more restrictive landscape regulations and guidelines, are discussed on the premise that they exert influence in developing and maintaining the long-term sustainability of ecosystems. In conclusion, this study provides the quantified landscape configuration and composition of the effects of development regulations on landscape structure. The ecologically planned community shows a less fragmented forest pattern and more restrictive development guidelines result in more ecologically structured environments. Understanding how elements of local development regulations affect ecological landscape patterns is important for landscape architects, planners, and administrators because it can lead to better strategies for planning and designing sustainable communities.Item Informing the carbon frontier : economics and landscape in the western Amazon(2016-08) Tasker, Kaitlin Allison Arford; Arima, Eugenio; Young, Kenneth RIn recent years, forestry carbon offset projects have been on the rise. While praised for their ability to offset emissions inexpensively, these programs are also criticized for their tendency to overlook other important social, environmental and economic processes. This thesis examines the site of a major carbon offset program in the western Amazon of Peru as a case study for multi-objective conservation planning. Using a recently released high resolution carbon dataset, this study first identifies areas of highest above ground carbon density. It then innovates by generating models for two additional conservation measures: forest connectivity and deforestation probability. While the forest connectivity model is informed by landscape ecology and is a more simple modification of least cost path, the deforestation model uses principles of economic rent to produce spatially explicit probabilities. By incorporating concepts of landscape ecology and economic rent, this work presents new models for the study area and adds to the theory surrounding multi-objective conservation planning. It also identifies if, how, and where three distinct conservation criteria can find commonalities. Unsurprisingly, the three criteria result in distinct spatial patterns. When all three are prioritized, less than 3% of the study area qualifies for priority. However, while this analysis highlights the difficulty of simultaneously prioritizing all three criteria, it also offers hope. Landscape-level analyses can help policymakers and conservation practitioners prioritize these limited areas while household-level and broader contextual information can help inform how initiatives are ultimately implemented. Given the limited area under all three criteria, stakeholders can strengthen efforts by encouraging connectivity-enhancing land use practices, incorporating areas where two criteria are met, or further facilitating nearby community involvement. As pressures to marry social, environmental and economic continue, incentive schemes will need to rethink these strategies and innovate, and further research should be conducted.Item Spatial variation in tree community assembly(2012-05) Lasky, Jesse Robert; Keitt, Timothy H.Spatial variation in tree community composition and assembly is due in large part to dispersal limitation, spatial variation in environmental conditions, and interactions among competing trees. The relative importance of these processes may be governed by landscape structure and environmental conditions. (I) The movement of frugivores between remnant forests and successional areas is vital for tropical forest tree species to colonize successional habitats. I found that avian frugivores crossing forest edges were generally insensitive to percent cover and clustering of pasture trees. If pastures were abandoned the distance from forest edges would not likely limit frugivore visitation and seed deposition under pasture trees in my study. (II) Relatively little is known from a theoretical conservation perspective about how reserve size affects communities assembled by abiotic and dispersal limitations. Simulated small reserve systems increased the distance between environments dominated by different species, diminishing the importance of source-sink dynamics. I found a trade-off between preserving different aspects of natural communities, with greater [alpha]-diversity in large reserves and greater [gamma]-diversity across small reserve systems. (III) Functional trait diversity of co-occurring organisms may be indicative of the processes that structure communities. Across spatial scales, an axis of leaf succulence exhibited the strongest evidence for niche-based assembly among co-occurring Ficus individuals, whereas specific leaf area (SLA) showed the strongest evidence for niche-based assembly among species. Trait analyses of co-occurring individuals had greater power than analyses at the species level, especially for traits with high intraspecific variation. Environmental filtering may be stronger at higher elevations due to drought stress. (IV) Individual fitness is a function of the interaction between traits and environment, or environmental selection. I estimated spatial selective gradients affecting a subtropical tree community and found that the trait axes with the strongest selection were also those with the least spatial variation. Interestingly, factors associated with selection were quite different for growth versus survivorship. The trait-by-environment interactions I identified are strong candidates for spatial niche differentiation, and may explain how tree species coexist in this diverse subtropical forest.Item Species diversity of aquatic macroinvertebrates in playa lakes: island biogeographic and landscape influences(Texas Tech University, 1997-12) Hall, Dianne L.Patterns of species diversity have long intrigued ecologists. This fascination has resulted in numerous theories explaining differences among sites in species diversity. Two such theories are those pertaining to island biogeography and landscape ecology. They differ in the import placed on patch versus matrix characteristics. Island biogeographic theory suggests that patch characteristics are the foremost influences on diversity. Conversely, landscape ecology proposes that attributes of the surrounding matrix are of primary significance. Playas of the Southern High Plains are an excellent environment in which to study the relative influence of patch versus matrix characteristics. They are numerous and surrounded by a mosaic of landuse practices. These ephemeral lakes differ greatly in size and contain an abundance of aquatic macroinvertebrates. Macroinvertebrates were sampled three times over a two month period and were categorized as resident or transient species based on life history characteristics. Species richness and diversity were analyzed for the effects of landuse practices, basin size, and surface area via analysis of covariance. In addition, G-tests of independence were used to analyze the influence of landuse practices and surface area on species composition. Surrounding landuse practices were found to influence resident species richness and species composition; total species richness was sensitive to basin size. Surface area affected total, resident, and transient species richness, resident species diversity, and species composition. However, all relationships were contingent on sampling period. Regression analyses revealed that resident species richness and diversity were influenced more by island biogeographic characteristics than by landscape attributes. However, the converse was true for transient species richness and diversity. Neither resident nor transient species richness and diversity were related strongly to differences in water quality. Both island biogeographic and landscape characteristics affect the diversity of macroinvertebrates in playa lakes. However, the extent of the influence of these two factors is dependent on life history strategy of the biota and time since inundation. The idiosyncratic pattern of species diversity is a reflection of the stochastic nature of playa inundation overlain by the effects of island biogeographic and landscape processes.Item Species diversity of aquatic macroinvertebrates in playa lakes: island biogeographic and landscape influences(Texas Tech University, 1997-12) Hall, Dianne L.Patterns of species diversity have long intrigued ecologists. This fascination has resulted in numerous theories explaining differences among sites in species diversity. Two such theories are those pertaining to island biogeography and landscape ecology. They differ in the import placed on patch versus matrix characteristics. Island biogeographic theory suggests that patch characteristics are the foremost influences on diversity. Conversely, landscape ecology proposes that attributes of the surrounding matrix are of primary significance. Playas of the Southern High Plains are an excellent environment in which to study the relative influence of patch versus matrix characteristics. They are numerous and surrounded by a mosaic of landuse practices. These ephemeral lakes differ greatly in size and contain an abundance of aquatic macroinvertebrates.Item “They are drying out” : social-ecological consequences of glacier recession on mountain peatlands in Huascarán National Park, Peru(2016-05) Polk, Mary Harding; Young, Kenneth R.; Crews, Kelley A; Knapp, Gregory W; McKinney, Daene C; Pérez, Francisco LEcosystems that are proximal to tropical glaciers, such as mountain peatlands in Peru’s Huascarán National Park, are experiencing ecological changes caused by glacier recession. Peatlands are not only affected by biophysical changes, but also by human behaviors and associated land use decisions that are influenced by changing environmental conditions. Thus mountain peatlands in Huascarán National Park are coupled natural human systems. Social-ecological system theory can be used to situate integrated research questions and methodologies addressing the transformations of coupled natural human systems. In this dissertation, a social-ecological systems framework called the Press-Pulse Dynamics model was applied to investigate peatland transformations related to climate change and land use decisions. Using social-ecological systems theory necessitates methodological pluralism because reliance on a single epistemology produces limited new knowledge. In this research, a set of quantitative and qualitative techniques were implemented to produce an integrated perspective on social-ecological peatlands. A 23-year spatio-temporal remote sensing analysis of peatlands showed that the ecosystems are losing area through processes of fragmentation, attrition, and isolation. Statistical evidence suggested that loss of glacier area and decreasing stream discharge are driving factors for peatland area change, but that in the future, precipitation may become a more dominant factor. Extensive in situ plant surveys indicated high alpha and beta diversity and that there are likely many more species to be added to the known peatland flora. Vegetation heterogeneity was explained by the abiotic factors of elevation, percent organic matter, bulk density, and cation exchange capacity. A series of ecological oral histories showed that local users of peatlands have observed spatial and ecological changes over their lifetimes. The observations by local people corroborated quantitative findings and substantiated the linked biophysical and social aspects that affect peatlands. Interconnections between social and biophysical processes in the PPD model suggest that future peatland stewardship responsibilities should be entrusted to local communities in close collaboration with the national park and non-governmental organizations who could provide technology transfer support. The dissertation contributes to and advances geography by innovatively bridging multiple perspectives through a social-ecological systems model to produce new biophysical and social knowledge about tropical mountain peatlands that are affected by glacier recession.