Biodiv Sci ›› 2010, Vol. 18 ›› Issue (3): 300-311.DOI: 10.3724/SP.J.1003.2010.300

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Impacts of grazing intensity and management regimes on aboveground primary productivity and compensatory growth of grassland ecosystems in Inner Mongolia

Rui Xue1,2; Shuxia Zheng1; Yongfei Bai1*   

  1. 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093

    2 Graduate University of the Chinese Academy of Sciences, Beijing 100049
  • Received:2009-10-19 Online:2010-05-20 Published:2012-02-08
  • Contact: Yongfei Bai

Abstract:

Based on the ongoing Sino-German grazing experiment, which was designed to test how grazing intensity and management regimes (traditional system vs. mixed system) would affect the aboveground net primary productivity (ANPP) and compensatory growth of a typical steppe ecosystem in Inner Mongolia dominated by Leymus chinensis and Stipa grandis. Our experimental treatments included two management systems (e.g., a traditional versus a mixed system) and seven levels of stocking (i.e., 0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha). The traditional system was managed with grazing and haymaking on two different areas. The mixed system was managed with a yearly shift between grazing and haymaking on the same area. The results showed that, with increasing stocking rate, aboveground net primary productivity (ANPP) declined in both traditional and mixed grazing plots. At high stocking rates, ANPP in mixed grazing plots was significantly higher than that in the traditional grazing plots. Our results were partially in agreement with the grazing optimization hypothesis. Under the two management regimes, and using different methods for estimating the annual ANPP, we observed overcompensation, equal-compensation, and under-compensation in plant growth along a gradient of stocking rates. Equal-compensation was generally observed in the low stocking rate plots, while under-compensation was found in the high stocking rate plots. For most systems, compensatory growth could be simulated with linear or quadratic models when the percent biomass eaten by sheep was used as an index for estimating the relative stocking rate. Our study suggests that stocking rate, grazing regime, topographic position, and methods for estimating the net aboveground productivity were all important factors determining the magnitude and directions of estimated ANPP responses to grazing.