Influence of rainfall in growing season and clipping intensity on aboveground biomass of Leymus chinensis steppe

The study on the biomass change of Leymus chinensis, Artemisia eriopoda, Cleistogenes squarrosa and community of L.chinensis grassland under different rainfall conditions by using rainfall shelter and irrigation to adjust natural rainfall and using clip frequency to adjust clipping intensity was conducted from 2005 to 2007. The result showed that the biomass of A. eriopoda , C. squarrosa and the community except L. chinensis were significantly decreased in R1 treatment (rainfall was reduced by 50%, P0.05).In R3 treatment (rainfall was increased by 50%), the biomass of A. eriopoda and C. squarrosa performed an increasing tendency, however both L. chinensis and community showed a decreasing tendency (P0.05). In C2 treatment (clipping frequency was increased), the biomass of L. chinensis, A. eriopoda and the community showed the significant increasing tendency (P0.05). In 2006 (rainfall was 311 mm), the biomass of A. eriopoda, C. squarrosa and the community except L. chinensis increased significantly compared to that in 2005 (rainfall was 216 mm, P0.05). In 2007 (rainfall was 290 mm, drought in spring), the biomass of L. chinensis and C. squarrosa decreased significantly compared to that in 2006 (P0.05), the biomass of L. chinensis was even lower than that in 2005. The coefficient of variation (CV) on biomass of C. squarrosa, A. eriopoda, L. chinensis and the community was 85.2, 58.3, 36.0 and 16.5 respectively and the difference was significant.