Estimation of meadow steppe yield and carrying capacity of meadow grassland in Hulunber region

The improved CASA model was used to estimate the net primary productivity (NPP) and the carrying capacity of Xieertala meadow steppe during growing season of 2009 in Hulunber region, and then output from the improved CASA model was validated by the field survey data during growing season of 2009. The results of this study indicated that the estimated NPP of Xieertala meadow steppe in Hulunber region showed a unimodal curve throughout the year, peaking in July with 71.92 g/m2 yield. NPP changes corresponded to circle of meadow steppe vegetation growth stage. The estimated NPP and actual NPP was not significantly different and they shared the similar trend in seasonal change, and the accuracy of the improved CASA model was 94.05%. The total community cover and the heights were significantly positive correlation with meadow steppe yield. The estimated yield of Xieertala meadow steppe in 2009 showed that the optimal carrying capacity was 7 562.40 cattle units and was lower than the actual carrying capacity, implying that overloading rate was about 13.37%.