荒漠草原生物量空间异质性对长期不同放牧强度的响应

Response of Spatial Heterogeneity of Biomass to Different Long-term Grazing Intensity in Desert Steppe

研究植物群落空间异质性及其动态是认识生物多样性和生态系统稳定性维持机制的基础。本研究以拥有20年放牧历史的内蒙古荒漠草原放牧试验样地中的植物群落地上生物量为研究对象,基于地统计学分析不同放牧强度下植物群落地上生物量空间异质性。结果表明:(1)放牧显著降低了植物群落地上生物量,对变异系数未发生显著影响;(2)通过半方差函数进行拟合发现,CK,MG和HG处理植物群落地上生物量空间格局均符合指数模型,LG处理符合高斯模型,且结构比大小随放牧强度降低;(3)通过分形维数发现,随着放牧强度增大,空间分布呈现了较明显的均质化趋势;(4)结合2D和3D空间分布图看出,CK和LG处理中植物群落地上生物量为斑块化分布,MG和HG地上生物量则为梯度分布,趋于均质化。由此可见,随着放牧强度增大,植物群落地上生物量空间异质性逐渐降低。

Study the spatial heterogeneity and dynamics of plant communities are the basis to understand the maintenance mechanism of ecosystem biodiversity and stability.The aboveground biomass of plant communities in a desert steppe grazing experimental site in Inner Mongolia with 20 years grazing history was studied.We analyzed the spatial heterogeneity of aboveground biomass of plant communities under different grazing intensities based on traditional and geostatistical methods.The results showed that:(1)grazing significantly reduced the aboveground biomass of plant communities.The variation coefficient of aboveground biomass did not change significantly along with different grazing intensities.(2)By fitting the semi-variance function,the aboveground spatial pattern of biomass in vegetation communities in CK,MG,and HG treatment conformed to the exponential model,LG treatment met the Gauss model,respectively,and the structural ratio was decreased with the grazing intensity.(3)Through fractal dimension,it was found that the distribution pattern of aboveground biomass under different grazing intensities was simple.With the increase of grazing intensity,the spatial distribution showed a more obvious trend of homogenization.(4)Combined with the 2D and 3D maps of spatial distribution,the above-ground biomass of vegetation in CK and LG treatment was patchy distribution,while MG and HG caused the above-ground biomass of vegetation to change from patchy distribution to gradient distribution,homogenizing the spatial pattern of above-ground biomass of plant community.In summary,with the increase of grazing intensity,the spatial heterogeneity of aboveground biomass of plant communities was decreased.