EVALUATION OF GRAZING PRESSURE ON STEPPE VEGETATION BY SPECTRAL MEASUREMENT, pp. 201-222
Authors: (Tsuyoshi Akiyama, Kensuke Kawamura, Ayumi Fukuo, Toru Sakai, Zuozhong Chen, Genya Saito, River Basin Research Center, Gifu University, Gifu, Japan, and others)
Abstract: Steppe grassland spreading over eastern Europe to eastern Asia is one of the largest grassland ecosystems in the world, which is precious but fragile. Last four decades the grazing pressure has been increasing due to increase of animal and human population in Inner Mongolia, China. It may affect on the grassland ecosystem, including grassland biomass, grass quality, and species diversity. But how can we achieve for maintaining the valuable ecosystems and sustainable livestock farming at the same time? We examined the relationship between grazing pressure and grassland vegetation using drastically improved information technology such as remote sensing, Geographic Information Systems (GIS) and Global Positioning System (GPS). The experiment was carried out at Xilingol steppe, where the annual precipitation is around 300 mm, and annual mean air temperature is around 0°C. In the former part of the chapter, we discussed how to evaluate the grazing pressure under free ranging condition utilizing multiple livestock farmers in the extended grassland without fences and borders. Standing against this problem, we put GPS on the shoulder of sheep to trace the daily traveling distance. Sheep herd moved between 11 and 12 km in a day during summer season. GPS also showed us the place and time where the sheep herd spent. Newly developed bite-counter clarified the number of biting during grazing separated from rumination. The time series of biomass and grass quality (in term of crude protein content) changes were successfully monitored by satellite vegetation indices such as Terra MODIS-EVI and NOAA AVHRR-NDVI. In the latter part, we examined the effects of grazing pressure on steppe vegetation in the same district. In 1960‘s, several pipe lines were buried inside grassland from lake to supply drinking water for animal. Opening mouths were set at 5 or 6 km intervals. Livestock villages were formed around the opening, therefore, surrounding grassland came under the influence of gradation of grazing pressure concentrically. Started from certain opening, we put quadrates on 4 directions at 1 km intervals until 5 km of distance. In addition of botanical composition survey, biomass, soil conditions and spectral reflectance measurements were executed at each plot. Vegetation cover, biomass and plant height increased in accordance with distance from opening. Both NDVIs obtained from radiometer at ground and Landsat image showed similar trend as biomass change. Botanical composition also changed. Land was almost bare around the opening, then some low palatable herbaceous plants are remained near the opening. Three or four km apart from opening, the original vegetation and biodiversity recovered and biomass became constant. Finally, we discussed effects of grazing pressure on steppe vegetation from a comprehensive stand point.