Browsing by Author "Laituri, Melinda J., advisor"

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Open Access
Early detection and rapid assessment of invasive organisms under global climate change
(Colorado State University. Libraries, 2009) Holcombe, Tracy R., author; Laituri, Melinda J., advisor; Stohlgren, Thomas J., advisor
Invasive species alter native species assemblages, effect ecosystem processes, and threaten biodiversity worldwide. Early detection and rapid assessment will help stem the problem, focusing managers attention on newly established invasive species before they spread. This is a big task requiring a coordinated effort and a centralized data sharing effort. One tool that can be used in this effort is Geographic Information Systems (GIS). GIS can be used to create potential distribution maps for all manner of taxa, including plants, animals, and diseases, and may perform well in early detection and rapid assessment of invasive species. As an example application, I created maps of potential spread of the cane toad (Bufo marinus) in the southeastern United States at an 8-digit Hydrologic Unit Code (HUC) level using regression and environmental envelope techniques. Equipped with this potential map, resource managers can target field surveys to areas most vulnerable to invasion. However, there is a general need in invasive species research to quantify the potential habitat of many invasive plant species. I was interested in modeling the shifts in suitable habitat over time, environmental space, and climate change. I used 4-km2 climate scenarios projected to the years 2020 and 2035 for the continental United States, to examine potential invasive species habitat distributions. I used maximum entropy modeling (Maxent) to create three models for 12 invasive plant species: (1) current potential habitat suitability; (2) potential habitat suitability in 2020; and (3) potential habitat suitability in 2035. These models showed areas where habitat suitability remains stable, increases, or decreases with climate change. Area under the receiver operating characteristic curve (AUC) values for the models ranged from 0.92 for Pennisetum ciliare to 0.70 for Lonicera japonica, with 10 of the 12 being above 0.83 suggesting strong and predictable species-environment matching. Change in area between the current potential habitat and the year 2035 ranged from a potential habitat loss of about 217,000 km2 for Cirsium arvense, to a potential habitat gain of about 133,000 km2 for Microstegium vimineum. These results have important implications for developing a triage approach to invasive species management under varying rates of climate change.
Open Access
Ethiopian socio-hydrology: geographies of development and change in the water tower of Africa
(Colorado State University. Libraries, 2017) Chignell, Stephen M., author; Laituri, Melinda J., advisor; Evangelista, Paul H., committee member; Leisz, Stephen J., committee member
Water access, sanitation, and security remain key foci of international aid and development initiatives. However, the increasing interconnectedness of hydrologic and social systems can cause such initiatives to have unexpected and cascading effects across geographic scales. This presents new challenges for meeting ever-growing demand, as distant and complex socioeconomic and environmental relationships, or "telecouplings," may significantly influence the outcomes and sustainability of development projects. Predicting future water scenarios thus requires both integrative and basic research into the structure and function of socio-hydrological systems. I explored these emerging concepts in Ethiopia, which is the source of water for much of the Horn of Africa and receives over half of its annual budget from foreign development aid. I analyzed the geography of water in Ethiopia from two perspectives. First, I used examples from the literature to identify water development initiatives in rural and urban settings and at local and national scales. I then situated these initiatives within the telecoupling framework to reveal underlying socio-hydrological relationships. My results indicate that water development is linking Ethiopia's hydrology with geographically distant communities and markets and creating new and often unexpected flows of people, material, and capital. This is resulting in cross-scale feedbacks among urbanization, geopolitics, and the food-energy-water nexus in Ethiopia. Second, I conducted basic research into alpine wetland dynamics in the Bale Mountains, which provide the only perennial source of water to highland communities and 12 million downstream water users in East Africa. I found that wetlands more than double in extent between dry and wet seasons, and that just 4% of the alpine zone is saturated year-round. I found evidence of a hydrological continuum based on geologic and glacial legacies, which suggests that geology is a principal control on alpine wetland hydrology in Bale. I used this to develop a typology of wetland function, which provides a baseline for future research into climate change impacts and surface-groundwater connectivity.
Open Access
Land use influences on adjacent ecological systems: implications for conservation planning
(Colorado State University. Libraries, 2009) Wade, Alisa Ann, author; Laituri, Melinda J., advisor; Theobald, David M., advisor; Hoeting, Jennifer A., advisor
This research investigated the spatial relationships between land uses, primarily urbanization, and adjacent ecological systems. As anthropogenic stressors encroach on protected areas and aquatic systems, the ecological functioning of those systems is reduced, and this has implications for natural resource management and conservation. I conducted three separate studies to address different research questions relating to land use and land cover-ecological system linkages. I assessed the vulnerability of conservation lands throughout the U.S. to adjacent anthropogenic threats and identified protected lands that are likely threatened by human activities as well as unprotected lands that offer opportunities for future conservation action. I also quantified the amount of residential development encroachment surrounding protected lands in the U.S., and I quantified how encroachment has altered the landscape structure around conservation lands nationally from 1970 through 2000, and forecast changes for years 2000 through 2030. Results from these two studies showed that there are a number of protected areas that are vulnerable to neighboring threats and that development has both reduced the buffer surrounding and the connectedness between protected areas. However, results also suggested that there are a number of options for future conservation action, although continued urbanization will limit these options. These studies indicate that conservation planning must consider adjacent land uses. However, the final study presented in this dissertation illustrated that conservation scientists and land managers must recognize the limitations of their approach when modeling the relationships between ecological systems and adjacent land use. I used a conceptual model of how land cover at different upslope scales influences aquatic integrity to show how different modeling approaches can substantially alter resulting inference. Results suggest that a modeling approach that incorporates ecological knowledge may provide more relevant inference for management decisions. A finding applicable to all three studies is that a key conservation strategy will be to work cooperatively with adjacent land owners and mangers to successfully manage both protected areas and aquatic systems.
Open Access
The relationships of forest and watershed characteristics to soil water retention, storm runoff, erosion, and wave attenuation in Vietnam
(Colorado State University. Libraries, 2009) Tran, Bao Quang, author; Laituri, Melinda J., advisor
Forests can have a profound impact on the hydrological cycles. Numerous studies in Vietnam, and elsewhere have examined the effects of vegetation cover and geomorphology on hydrological processes at both watershed and regional scales, but the effects of forests in water yield, regulating seasonal water flows, and soil erosion are still in debate. This dissertation focuses on obtaining a deeper understanding about how forests, weather and geomorphology affect hydrological responses and soil erosion in Vietnam. Dissertation is a collection of four independent studies. The first study characterizes soil water retention of four forest types representing different levels of forest degradation. The results suggest that soil water retention, a function of soil moisture, bulk density, and soil depth; varies among forests, and it depends primarily on litter cover, vegetation cover, and porosity. Forest soil moisture can be predicted by a regression model, with the root square mean error of 3%. The second study investigates effects of watershed characteristics on runoff in 15 typical watersheds. The watershed factors, which include watershed size, shape, slope and elevation difference, forest cover and distribution, are analyzed in relation to increasing and decreasing peak flow, and daily streamflow variation, in which forest cover and distribution, shape, and elevation difference are found to be significant impacts on storm runoff. Relationships between peak discharge and initial flow and rainfall are statistically significant in this study. The third study is to define minimum forest areas for protection soils from erosion. A soil loss prediction equation and soil loss tolerance of 10 ton ha-1y-1 are used to generate an erosion risk map and vegetation index for Vietnam. Required forest areas are calculated by comparison erosion risk with vegetation index. Finally, wave attenuation is analyzed in relation to initial wave height, cross-shore distances, and mangrove forest structures. From these relationships, minimum mangrove band width for coastal protection from waves is defined and ranges from 40 m to 240 m depending on mangrove structures.
Open Access
Trends and processes of land cover change in the western High Plains ecoregion
(Colorado State University. Libraries, 2007) Drummond, Mark A., author; Laituri, Melinda J., advisor
The goal of this study was to better understand the agricultural land use processes and land cover changes affecting the semi-arid Western High Plains ecoregion in the United States Great Plains. Globally, the processes of agricultural expansion and loss have had widespread effects on land cover and ecosystems that are an ongoing concern of land change research. To improve the understanding of regional land change, three main topics were addressed: (1) the contemporary patterns and key processes of agricultural change in the conterminous United States; (2) the rates, causes, and processes of land cover change in the Western High Plains ecoregion between 1973 and 2000; and (3) the primary driving forces of contemporary land cover change in the Western High Plains, including the dynamics of water resource access. Land cover change estimates for the ecoregion were derived using a stratified random sample of 10 x 10 km blocks and remote sensing change detection. Land use was examined using the Census of Agriculture. Results of the study indicate that patterns of land change vary by region and time period depending on socioeconomic driving forces and environmental context. In the Western High Plains ecoregion, net grassland loss occurred from 1973 to 1986 as agricultural land expanded in response to market opportunities. Agricultural expansion affected 1.9% of the ecoregion. Processes of land change became substantially different after 1986. Between 1986 and 1992, grassland expanded and became the dominant land cover, driven in large part by the cropland retirement policies of the Conservation Reserve Program (CRP). Agricultural declines affected 7.3% of the ecoregion, primarily as cropland was converted to grassland cover. Between 1992 and 2000, net grassland expansion was less than 1%, although there was a high rate of gross change in the location of grassland and agriculture that had only a limited effect on net change. The primary driving forces of land cover change were enabled by water resource access, which had a substantial influence on grassland extent and pattern.