Consistent use of vegetation indices (VIs) for monitoring rangeland ecosystems in Middle Asia, and particularly Uzbekistan has been limited. In the face of intense rangeland degradation in Uzbekistan, understanding the applicability of VIs is an immediate priority for the assessment of the current state of these rangelands. This article focuses on comparing and evaluating the potential of five intensively used VIs (NDVI, SAVI, EVI, PVI and TSAVI) to detect changes in condition and productivity of Artemisia spp. rangelands across different seasons and years. The results indicate a high degree of similarity in the response of the tested VIs when multi-season and multi-year vegetation data were combined. However, there was significant variability when vegetation data were parsed into seasons and/or variable precipitation years. We recommend that a remote sensing assessment of rangelands in various stages of invasion by native non-palatable plants should rely on a multi-season analysis of NDVI or SAVI.
Abstract Many land‐management agencies are caught between decreased budgets and increasing public interest. Furthermore, semi‐arid landscapes are sensitive to management prescriptions and use, and require a significant amount of monitoring in order to assess vegetation productivity and health. The purpose of this study was to evaluate the use of Landsat Enhanced Thematic Mapper (ETM) Imagery to monitor seasonal vegetation cover in a shrub‐steppe ecosystem. The study area, managed by The Utah School and Institutional Trust Lands Administration, consists of a shrub‐steppe environment in south‐central Utah. Biotic (tree, shrub, grass, and forbs) and abotic (slope, aspect, elevation, landform type, and slope shape) data were collected during the 2001 growing season and compared with three dates of Landsat ETM satellite imagery. The relationships between remotely sensed parameters, photosynthetically active ground cover and bare ground were significant. Stepwise linear regression for total vegetation cover identified the ETM bands 2, 4, and 5 with NDVI as the strongest predictor variables (r2 = 0.86, p < 0.01). Combined predictor values for bare ground using ETM bands 3, 4, 5, and 7 with NDVI had a stronger relationship (r2 = 0.92, p < .01). Correlations between percent vegetation cover estimates versus ETM individual reflective bands and NDVI showed little relationship between vegetation cover and the NIR (band 4) but a strong relationship with NDVI for this semi‐arid landscape. Remote sensing information may be the key for public and private land mangers to make optimal economic and environmental decisions regarding use of state, public, and private rangelands.
Abstract Abstract The purpose of this study was to identify the ecological effects of drought on the vegetation resources of subsistence agropastoral communities on the Bolivian Altiplano. The objectives of the study were to (1) characterize vegetation cover response during a typical year, and (2) identify vegetation cover type's response to drought using an image differencing change detection technique. A geographical information system (GIS), which included multi-temporal (from 1972-1987) Landsat satellite imagery, was used as the assessment tool. Vegetation index difference images showed that (1) all vegetation types were impacted by drought, but the wet meadow vegetation cover type had the least response, and (2) approximately 90 per cent of vegetation cover had not changed between 1972 and 1987. Crop and animal production in agropastoral systems are dependant on the availability of vegetation resources. The wet meadow vegetation type was the most resistant to drought, which suggests that during drought periods it is a key resource upon which the livestock of the community would depend. Little change in vegetation cover over the 15-year span of the study, and the rapid recovery of this parameter following the drought of 1983-84, suggest that agricultural practices (especially livestock grazing) are not contributing to resource degradation when measured only in terms of change in vegetation cover.
An accuracy assessment of the Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation continuous field (VCF) tree cover product using two independent ground‐based tree cover databases was conducted. Ground data included 1176 Forest Inventory and Analysis (FIA) plots for Arizona and 2778 Southwest Regional GAP (SWReGAP) plots for Utah and western Colorado. Overall rms. error was 24% for SWReGAP and 31% for FIA data. VCF bias was positive at low observed tree cover but systematically increased thereafter until at greater than 60% observed tree cover, VCF tree cover was 40% (SWReGAP) to 45% (FIA) too low. Errors are unlikely to be related to habitat fragmentation or variation in canopy height but may be influenced by scaling discontinuities between ground and satellite resolutions.
The purpose of this paper was to evaluate the feasibility of conversion from dryland to paddy field in Jinxian County under the water resources constraint and dryland suitability condition. We constructed a water resources balance model to evaluate irrigation needs and a dryland suitability model that coupled various spatial data layers. Our research showed that under the water resources constraint, the amount of conversion from dryland to paddy field was 26,971.69 ha and the feasible conversion degree of dryland to paddy field was 0.84, while under the dryland suitability condition, it was 23,262.74 ha and 0.72, respectively. According to the principle of maximum constraint, we conclude that the feasible conversion degree of dryland to paddy field was 0.72. This research can provide an objective and scientific basis for carrying out a programme of farmland conversion in counties of China as well as similar areas worldwide.
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