Estimation the Rangeland Vegetation Cover of Tange Sayyad Region (Chaharmahal va Bakhtiary Province) Using IRS LISS-III Data

IntroductionRangelands encompass about 55% of Iran's total area. These lands are the habitat of Iranian nomads and their animals. The extension, variations in climate, soil and vegetation cover require specific management. Having knowledge about the vegetation parameters, especially the coverage, is highly significant for efficient utilization and erosion control of the rangelands. Vegetation cover is defined as the percentage of ground covered by live vegetation within a given reference area such as a plot. Normally vegetation cover is measured using a reference frame, a ring, a square or a circle. The reference frame allows the researcher to focus on a small area (depending on the size of the frame) and estimate vegetation cover versus bare rangeland areas. Point-intercept and line-intercept methods were suggested by some researchers. Vegetation cover is an indicator for some environmental indices. For instance, Amaral, et al. (2007) applied normalized difference vegetation index (NDVI) along with climatic and topographical factors for the probability distribution of five plant species. They reported that the application of NDVI had increased the efficiency of models. Firmino, et al. (2009) studied the relationship between NDVI and precipitation. They concluded that NDVI is a spatial function of precipitation. Using remote sensing techniques for the monitoring of vegetation cover in rangelands of Iran is inevitable due to the extensive and dynamic behavior of these land covers. Normally, using remote sensing for vegetation monitoring corresponds to the application of vegetation indices, which are suggested to minimize the external impacts on spectral data and determining vegetation cover and leaf area index. Taylor et al. (1985) reported the existence of significant correlation coefficients between biomass and grass-prosopis cover, and NDVI and ratio vegetation index (RVI), calculated from NOAA-7 data. Rondeaux, et al. (1996) compared the correlation coefficients of six vegetation indices of SAVI, OSAVI, TSAVI, GEMI, NDVI and MSAVI with vegetation cover and reported that MSAVI is the most sensitive index to vegetation cover. Zhaa, et al. (2003) studied the vegetation cover of grasslands in Western China using 68 plots, and reported that NDVI had the highest correlation coefficient with vegetation cover percentage. Madoganda et al. (2008) assessed biomass and leaf area index of deciduous forests of Westchatz in India, by using IRS-P6 LISS-IV. They reported existence of positive correlation coefficients between satellite data and leaf area index and biomass. Tang e Sayyad National Park is the habitat of precious wild life in the semi arid zone of Charmahal-o-Bakhtiari Province. Assessing the vegetation cover of this national park contributes to management, indirect estimation of animal capacity, and soil conservation of the park. This study was carried out at the early season of drought of 2008.