微生境尺度上放牧退化草原群落特征与土壤有机质的空间分异性

 格局和过程与异质性有关。以呼伦贝尔克氏针茅草原不同放牧强度下的演替群落为对象,开展群落植被空间分布格局及土壤有机质空间异质性研究。结果显示,不同放牧强度样地群落结构和群落种类组成存在明显差异。轻度放牧样地样方内有8种植物,群落优势种为克氏针茅（Stipa krylovii）;中度放牧样地样方内有12种植物,群落优势种为糙隐子草（Cleistogenes squyarrosa）;而重度放牧样地样方内只有7种植物,群落优势种为多根葱（Allium polyrhizum）。随放牧强度的增强,植被地上生物量及其变异系数逐渐降低;土壤有机质含量表现为轻度放牧>中度放牧>重度放牧,而其变异系数表现为中度放牧>轻度放牧>重度放牧。从植被地上生物量和土壤有机质含量变异函数分析来看,随放牧压力的增大,植被地上生物量空间自相关性增强,空间异质性变大;土壤有机质含量空间分布自相关性先增强,然后减弱,空间变异性先变大,然后变小。在10 cm×10 cm的微尺度上,重牧群落植被地上生物量和土壤有机质含量之间表现出明显的相关性（P<0.05）。

Micro-scale Spatial Heterogeneity of Vegetation Community and Soil Organic Matter under Different Grazing Intensities

Both vegetation pattern and population process have relationship with spatial heterogeneity.In this study,we compared the spatial distribution of the aboveground biomass and soil organic matter in three communities of Stipa krylovii steppe under different grazing intensities.The vegetation community compositions vary with different grazing pressures.The dominant species are Stipa krylovii,Cleistogenes squyarrosa,and Allium polyrhizum in the light,moderate,and heavy grazing communities,respectively.There are eight plant species in the light grazing community,twelve plant species in the moderate grazing community,and seven plant species in the heavy grazing community.(2) Both the aboveground biomass and its variation coefficient decrease with increase of grazing intensity;the sequence of soil organic matter content within 10 cm depth is,light grazing>moderate grazing>heavy grazing and the variation coefficient of soil organic matter is ranked as: moderate grazing>light grazing>heavy grazing.(3) Geostatistical analysis results show that the spatial heterogeneity of aboveground biomass increases with the increase of grazing intensity,and the spatial heterogeneity of soil organic matter within 10 cm depth is ranked as: moderate grazing > light grazing>heavy grazing.(4) At 10 cm×10 cm spatial scale,there is significant correlation between the aboveground biomass and the soil organic matter contents only in the heavy grazing site(P<0.05).