Brandts voles Impact of Brandts voles on grassland vegetation under simulated conditions 1 Impact on vegetation biomas

The impact of Brandts voles (Lasiopodomys brandtii) with different densities on aboveground biomass and compensation growth of grassland were studied under simulated conditions in Xuanping Country of Hebei Province from May to October, 2007. The results indicated that 1) the relationship between the vegetation aboveground biomass and vole density showed a parabolic curve, the vegetation biomass increased while the vole density was less than 5 voles/100 m2 and it reached the peak value at the density of 5 voles/100 m2, but it decreased while the density was over 5 voles/100 m2; 2) the relationship between compensation growth and vole density showed one single peak curve and the compensation growth reached the highest while the vole density was 8 voles/100 m2; 3) the vole density that vegetation could stand was 4 voles/100 m2 (or 400 voles/hm2) and the plant growth could be stimulated and the vegetation community structure could be stabilized while the density was less than 4 voles/100 m2.