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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Seasonal densities and habitat use of desert mule deer in a semidesert grassland

Koenen, Kiana Kathleen-Gaye January 1999 (has links)
I determined density and habitat use of desert mule deer (Odocoileus hemionus crooki) on the Buenos Aires National Wildlife Refuge, a semidesert grassland in southeastern Arizona, in 1996. I observed 219 groups of deer; densities varied from 0.9 ± 0.3 (SE) deer/km² in summer to 2.5 ± 1.3 in winter. Herd size varied from 1.5 ± 0.1 deer/group in summer to 9.7 ± 2.0 in winter. Density of females was greater than males (0.9 ± 0.3 and 0.03 ± 0.04, respectively). Mule deer used subshrub-grass more in summer (χ² = 54.8, 6 df, P < 0.0001) and Russian thistle (Sallsola kali) less and cactus more in autumn (χ² = 60.2, 6 df, P < 0.0001) than expected. Deer used mesquite (Prosopis velutina) less than expected, which may have been due to the difficulty of observing deer in dense cover. In general, the mule deer population was widespread, had a high proportion of females, and used vegetation associations as available.
42

Effects of mesquite control and mulching treatments on herbaceous productivity and soil properties

Pease, Stacy Gale January 2000 (has links)
The objective of this study was to evaluate the effects of mesquite overstory removal and modifications of soil properties due to mulching treatments on herbaceous production. The three overstory treatments were complete removal of mesquite overstory with no removal of regrowth, complete removal of mesquite overstory with removal of regrowth and an untreated control. The mulching treatments included applications of chip mulch, commercial compost, lopped-and-scattered mesquite branchwood and a control. Both overstory treatments resulted in an increase of over 20% in total annual herbaceous production. The overstory treatment of complete removal of mesquite overstory with no removal of regrowth had the greatest impact on fall production of native herbaceous species during years of relatively high precipitation, at times increasing production by almost 2-fold. Mulching treatments had no effect on herbaceous production; however, soil pH and plant available phosphorus was affected by some of the mulching treatments.
43

Optical-biophysical relationships and validation of MODIS vegetation indices with multiple fine spatial resolution data in semiarid rangelands

Gao, Xiang January 2001 (has links)
The vegetation index products from the Moderate Resolution Imaging Spectroradiometer (MODIS) are designed to provide consistent, spatial and temporal comparisons of global vegetation conditions. The objective of this dissertation was to validate the robustness and global implementation of two MODIS VI algorithms, including the normalized difference vegetation index (NDVI) and "enhanced" vegetation index (EVI). Their performances have been evaluated in: (1) the normalization of canopy background (brightness) variations and the extraction of biophysical parameters across different canopy structures; (2) the characterization of seasonal vegetation profiles (phenological, intra-annual); and (3) spatial and temporal discrimination of vegetation differences (inter-annual). The validation was accomplished through multiple means, including canopy radiative transfer models which were utilized to extract pure vegetation spectra and "true" VI value free of background contamination for varying canopy structures and vegetation amount. The experimental field- and airborne-based radiometry and satellite imagery at multiple spatial resolutions were also coupled and scaled-up for comparison with coarse spatial resolution MODIS VI products to quantify characteristics of semiarid rangeland vegetation. The results showed that NDVI was advantageous in yielding biophysical relationships applicable across varying canopy types, but required knowledge of soils for biophysical estimations. The EVI provided biophysical relationships sensitive to canopy structure, thus requiring knowledge of canopy type for biophysical assessments. The MODIS VI products were successfully validated, radiometrically, by coupling field and the MODLAND Quick Airborne Looks (MQUALS) observations to high spatial resolution imagery (AVIRIS and ETM+), and appeared robust across the two parallel sites for depicting their ecological equivalents. MODIS multitemporal VI profiles were able to depict phenological activity, length of the growing season, peak and onset of greenness, and leaf turnover. Among the sensors tested, spatial resolution was found to be most important for discriminating the major land cover subtypes within the two parallel semiarid rangelands, and spectral resolution had major effects on capturing seasonal contrast due to atmosphere influences. The validation strategy utilized in this study to successively aggregate the integrity-inherent multiple fine spatial resolution data to the coarse MODIS pixel sizes appeared to perform well, thus showing potentials in the validation of other satellite products.
44

Landscape perceptions and natural resource management: Finding the 'social' in the 'sciences'

Toupal, Rebecca Stuart January 2001 (has links)
Multi-cultural demands of public lands in the United States continue to challenge federal land managers to address social and cultural concerns in their planning efforts. Specifically, these individuals lack adequate knowledge of cultural concerns as well as a consistent strategy for acquiring that knowledge for use in decision-making. Current federal approaches to cultural concerns include public participation, conservation partnerships, government-to-government consultations with American Indian tribes, cultural resource inventories, and landscape analysis. Since cultural knowledge arises from human-nature relationships and shared perceptions of natural environments, and landscapes are the ultimate expression of such knowledge, an exploratory methodology was developed for a different approach to understanding cultural concerns through landscape perceptions. Using cultural landscape theories and applications from the natural and social sciences, this study examined the landscape perceptions of four groups concerned with management planning of the Baboquivari Wilderness Area in southern Arizona: the Bureau of Land Management, landowners of the Altar Valley, recreationists, and members of the Tohono O'odham Nation. The methodology is based on a human nature relationships rather than cultural aspects or features. It takes a holistic approach that differs from other perception studies by including: emic aspects of data collection and analysis; a spatial component: triangulation of data collection through narrative and graphic descriptions; conducting ethnographic, on-site interviews; and consensus analysis and small-sample theory. The results include: verification of four cultural groups; two levels of consensus---in the population of concern, and in each group---that overlap in some aspects of landscape perception; descriptions of four cultural landscapes that illustrate similarities and differences among the groups, and include patterns and representations of spatial relationships; an effective methodology for revealing cultural concerns that are not identified through public forums, and with potential for application by agencies at the field office level.
45

Prescribed fire and ecosystem management: Managerial considerations for longer temporal and broader spatial scales

Keating, Brian Elliott, 1968- January 1995 (has links)
Ecosystem management is positioned as the modern paradigm of resource management. Fire management activities within the natural resource management agencies, under the adoption of an ecosystem management approach, supports an increased focus upon prescribed and manager-ignited fire programs. A review of past national fire policies and the effects they have had upon ecosystem conditions today further supports the role for prescribed fire. Under an ecosystem management approach, resource managers need to consider the effects of fire management activities over longer temporal and broader spatial scales. Examining the ecological, social, political, and economic aspects surrounding fire management activities on these scales will help ensure healthier ecosystems in perpetuity. Although the suppression of wildfires will remain a necessary component to fire management activities today, there needs to be an increased effort to reintroduce fire into ecosystems and to recognize fire as a natural component vital to maintaining ecosystem health.
46

Extracting temporal and spatial information from remotely sensed data for mapping wildlife habitat

Wallace, Cynthia S.A. January 2002 (has links)
The research accomplished in this dissertation used both mathematical and statistical techniques to extract and evaluate measures of landscape temporal dynamics and spatial structure from remotely sensed data for the purpose of mapping wildlife habitat. By coupling the landscape measures gleaned from the remotely sensed data with various sets of animal sightings and population data, effective models of habitat preference were created. Measures of temporal dynamics of vegetation greenness as measured by National Oceanographic and Atmospheric Administration's Advanced Very High Resolution Radiometer (AVHRR) satellite were used to effectively characterize and map season specific habitat of the Sonoran pronghorn antelope, as well as produce preliminary models of potential yellow-billed cuckoo habitat in Arizona. Various measures that capture different aspects of the temporal dynamics of the landscape were derived from AVHRR Normalized Difference Vegetation Index composite data using three main classes of calculations: basic statistics, standardized principal components analysis, and Fourier analysis. Pronghorn habitat models based on the AVHRR measures correspond visually and statistically to GIS-based models produced using data that represent detailed knowledge of ground-condition. Measures of temporal dynamics also revealed statistically significant correlations with annual estimates of elk population in selected Arizona Game Management Units, suggesting elk respond to regional environmental changes that can be measured using satellite data. Such relationships, once verified and established, can be used to help indirectly monitor the population. Measures of landscape spatial structure derived from IKONOS high spatial resolution (1-m) satellite data using geostatistics effectively map details of Sonoran pronghorn antelope habitat. Local estimates of the nugget, sill, and range variogram parameters calculated within 25 x 25-meter image windows describe the spatial autocorrelation of the image, permitting classification of all pixels into coherent units whose signature graphs exhibit a classic variogram shape. The variogram parameters captured in these signatures have been shown in previous studies to discriminate between different species-specific vegetation associations. The synoptic view of the landscape provided by satellite data can inform resource management efforts. The ability to characterize the spatial structure and temporal dynamics of habitat using repeatable remote sensing data allows closer monitoring of the relationship between a species and its landscape.
47

Spatial and seasonal variations along the US-Mexico border: An analysis with Landsat Thematic Mapper imagery

De Lira-Reyes, Gerardo, 1960- January 1997 (has links)
Research in global ecology has been concerned with the effect of vegetation removal in semi-arid regions including aspects such as plant succession and desertification and its impact on global change, specifically global warming. In addition, conditions along international borders often are presented as discontinuities in terms of vegetation and soil status. To better document these discontinuities in a semi-arid region, a multi-temporal study along the U.S.-Mexico border was conducted with a series of six Landsat Thematic Mapper (TM) images acquired over the 1992 growing season. Spatial and temporal variations across the border were analyzed with reflectance data. Spatial data was obtained from three different sampling size areas which included: the Parker Canyon grassland; the San Rafael Valley, a grassland combined with riparian areas and croplands; and the regional area along the Arizona-Sonora border including valleys and mountains, and diverse vegetation communities and soil conditions. These areas consisted of about 106 ha, 5,800 ha, and 738,000 ha, respectively, at each side of the border. Temporal data were obtained from the six TM images which were acquired in days of the year 162, 178, 194, 274, 306, and 322. Four remote sensing applications were considered for comparison studies on both sides of the border. These techniques included: (a) band comparisons, (b) albedo, derived from the discrete sensor band information, (c) vegetation indices, and (d) application of a linear mixing model. When comparing both sides of the border, significant differences were observed in most of the remote sensing techniques applied at the Parker Canyon area. Higher differences were found during the wet season with all of the applied techniques with the exception of albedo. The red band and albedo were the most important discriminants during the dry season. At the intermediate size, San Rafael Valley area, U.S.-Mexico differences followed the same pattern as Parker Canyon, but statistically, these differences were deemed insignificant. At the regional area, no differences were observed between the U.S. and Mexican side. The effect of pixel aggregation using the different remote sensing techniques and ground data from field campaigns in 1995 were also analyzed.
48

Strategies for enhancing local support for wildlife conservation in Maasai land, Kenya

Ole Seno, Simon Kasaine, 1953- January 1998 (has links)
The primary goal of my study was to evaluate strategies for promoting local support for wildlife conservation in Masai Mara National Reserve (MMNR) and the adjacent group ranches. This was done by determining the effects of the changing land tenure from communal to individual on the Maasai lives and wildlife, and the role of the revenue sharing program in enhancing support for wildlife conservation. The study used local people's suggestions to recommend strategies for improving revenue sharing. A combination of literature review, questionnaire-based surveys and participant observation methods were used to achieve these goals. The maintenance of a viable ecosystem in Mara has succeeded due to the traditionally benign relationship between the Maasai and wildlife. However, various factors continue to strain this relationship. First, increasing human population and encroachment of agriculture has diminished areas available for livestock and wildlife grazing. Second, the absence of compensation for loss of life and property to wildlife and inadequacy of the revenue sharing has increased people's antagonism towards wildlife. Third, since the local people are excluded from the management of MMNR and wildlife in general, they consider these activities external impositions. Fourth, subdivision of group ranches will severely reduce the land available for livestock and wildlife grazing and eliminate the traditional resource sharing strategy that has sustained the Maasai for centuries. This study also revealed that although the Maasai harbor many negative feelings towards MMNR, they consider it an important asset. Further, they are unwilling to give up pastoralism and expect to continue with communal grazing after subdivision which, is good for wildlife conservation. In view of this, I made the following recommendations: implement a regional land management system with a core wildlife area (the reserve) and a wildlife management-pastoral area surrounding the core, and designated zones for agriculture; support the above system with firm government policies and incentives; redesign the revenue sharing program to cover all the affected people; promote policies that encourage diversified wildlife-based enterprises including consumptive use; transfer much of the wildlife management responsibilities to the local people.
49

Biotic and abiotic constraints on shifts in temperate savanna ecotones at lower treeline

Weltzin, Jake Frederick, 1964- January 1998 (has links)
In contrast to documented increases in woody plant dominance of former savannas and grasslands of North America, oak (Quercus L.) savannas that form lower treelines in the southwestern United States and northwestern Mexico have been relatively stable over the past millennium. This research identified potential biotic and abiotic constraints on seedling recruitment of Quercus emoryi Torr. (Emory oak) within the context of potential shifts in lower treeline. Field surveys were used to describe seedling distribution at and below lower treeline, and to determine the potential for acorn dispersal from lower treeline into adjacent grassland. Field and greenhouse experiments designed to determine constraints on seedling establishment included reciprocal soil transfers, nutrient amendment studies, provision of artificial shade, and manipulation of seasonal precipitation inputs. Results indicate that rates of Q. emoryi recruitment within grasslands below treeline are relatively low, and are constrained by low rates of seed dispersal coupled with a low probability of seedling emergence. Seedling recruitment rates were directly correlated with quantity of summer precipitation, but were independent of winter precipitation. Results of this and complementary research suggest that lower treeline in southern Arizona is stabilized by self-enhancing feedback mechanisms of overstory shade, seed dispersal, and seedling establishment coupled with strong abiotic constraints beyond the current ecotone. The observed shift in treeline in the last millennium was less likely the result of slow, spatial progression of autogenic safe sites than the result of episodic and infrequent allogenic processes that simulated, or negated the importance of, conspecific, biogenic safe sites. Increases in summer precipitation are one such process that would facilitate (historic or potential future) downslope shifts in lower treeline. This interpretation is consistent with observations that downslope shifts in lower treeline which occurred 700-1700 ybp coincided with a period of particularly high summer precipitation in the region (i.e., the "Medieval Warm" period, 645-1295 ybp).
50

The effectiveness of public/private conservation partnerships as measured by common characteristics of success

Toupal, Rebecca Stuart, 1957- January 1997 (has links)
Conservation partnerships are working throughout the United States to address natural resource problems in watersheds. These projects have levels of complexity that challenge successful accomplishments. This study investigates what constitutes success in watershed partnerships and what measures may define success. Characteristics are identified from a literature search to create a success model. Characteristics of three partnerships led by the U. S. D. A. Natural Resources Conservation Service, Conservation Districts, and Resource Conservation and Development councils are compared to the model. Analyses address frequencies of occurrence of characteristics and differences between public and private responses. The results do not support the success model. Eight common characteristics of success are found in the case studies. Six of these characteristics are of a qualitative nature indicating a need to include qualitative measures with quantitative measures of success. The development of an effective guide for successful conservation partnerships is based on the eight characteristics.

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