[Variation of soil physicochemical and microbial properties in degraded steppes in Hulunbeir of China]

Abstract

To investigate the influence of degradation on grassland, we sampled soil and plants at three sites respectively under light, moderate and severe degradation in Hulunbeir Grassland in northern China and analyzed the differences and relationships among soil physicochemical characters, enzyme activity, soil microorganism quantity and aboveground biomass. The results showed that species richness of the moderately degraded site was highest while the aboveground biomass at the lightly degraded site was significantly higher than at the severely degraded site. Soil moisture content, nutrients (organic matter and total nitrogen) concentrations, soil microorganism quantity and enzyme activity were all decreased significantly in the degraded sites, whereas both the soil hardness and bulk density showed an opposite trend. The soil microbial biomass carbon and nitrogen contents ranged from 128 to 185 g x kg(-1) and from 5.6 to 13.6 g x kg(-1), respectively. The soil dehydrogenase and urease activities negatively correlated with soil bulk density but positively correlated with total nitrogen, organic matter, microbial biomass carbon and nitrogen. The aboveground biomass showed significantly positive correlation with the number of soil bacteria and fungi.