Effect Of Grazing On Community Characteristics, Soil Properties And Species Diversity Of Stipa Baicalensis Steppe

The study site was located in the Stipa baicalensis steppe, Yimin River, Hulunbeir of Inner Mongolia. The field investigation and indoor mathematical analysis were conducted for discussing the steppe's standing crops and the relationships between plants, soil and species diversity under grazing. The investigation was carried out from July to August, 2004 and August, 2005. It was extremely drought in 2004 because the rainfall was only about half of the average, and there was abundant rainfall in 2005. The major results were as follows:(1) The aboveground standing crops decreased with the increase of grazing intensity in both 2004 and 2005. The aboveground standing crop in 2004 was lower than that in 2005. The underground biomass and the ratio of aboveground standing crop to the underground biomass decreased with the increase of grazing intensity in 2004. The underground biomass in non-grazing (CK), light-grazing (LG), moderate-grazing (MG) and heavy-grazing (HG) were 7448.5, 7110.2, 6980.8 and 4282.6g/m2 respectively. The vertical distribution of the underground biomass accorded with exponential relation in 2004, the equation was y=aebx ( y was underground biomass, g/m2; x was soil depth, dm ). The ratio change of aboveground standing crops of Stipa baicalensis to Artemisia frigida and leymus chinensis to Artemisia frigida in two years was similar, that was CKHG>MG>LG.(4) The correlation analysis of the community standing crop, physical and chemical properties of soil and species diversity showed that the Simpson index was significantly negatively correlated with total K, total P, the aboveground standing crop and the underground biomass at the level of P<0.01; was significantly positively and negatively correlated with the soil rough particle and fine particle at the level of P<0.05 respectively。The aboveground standing crop was significantly positively correlated with total K, total P and quantity of fine particle at the level of P<0.05; was significantly positively correlated with the quantity of soil powder-clay particle and the underground biomass at the level of P<0.05; was significantly negatively correlated with the quantity of rough particle at the level of P<0.01.