Quantifying grazing intensities using geographic information systems and satellite remote sensing in the Xilingol steppe region, Inner Mongolia, China

Satellite remote sensing can be used to assess grazing intensities and provide information on grassland management. A methodology was developed for quantifying the effects of grazing intensities (GI) using the normalized difference vegetation index (NDVI) obtained by the moderate resolution imaging spectroradiometer (MODIS) on-board the earth observing system (EOS) terra satellite. A combination of GPS (global positioning system) and GIS (geographic information system) was used. The study area in the Xilingol steppe lies in a semi-arid region and is dominated by typical steppe and the marshy meadow vegetation on the Xilin riverside area in Inner Mongolia. It covers a total area of approximately 20 km2, and is grazed by sheep and goats. The relationship between MODIS/NDVI and observed plant biomass (g DM m−2) showed a significantly positive correlation (R2 = 0.447, P < 0.01). To quantify grazing pressure, a GI map of three herds of sheep was created using a grid cell method with the tracking data recorded by the GPS. The relationship between GI and estimated plant biomass revealed a poor negative correlation (R2 = 0.217, P < 0.01). It indicated that plant biomass reduced with increasing GI. When the plant biomass data was separated into two different vegetation types, marshy meadow and typical steppe, a stronger negative correlation was obtained (R2 = 0.887, P < 0.001). This suggested that the water environment was affected by both the sensitivity of the spectral reflectance of the MODIS sensor and by plant productivity in different vegetation areas. From these results, GPS/GIS was revealed as being a useful tool for quantifying grazing distribution in Inner Mongolia grasslands. It was further suggested that the combined use of satellite images with GPS/GIS could be considered for estimating the effects of GI on plant biomass. It might provide useful information about the sustainable use of grasslands for range managers.