The Study Of Biomass, Belowground Productivity And Their Relationship With Environmental Factors In Inner Mongolia Grassland

In order to explore the distribution pattern of species diversity, biomass and belowground productivity andtheir response to environmental factors in Inner Mongolia temperate steppe, using belt transect method, wesettled33sample sites along the water and thermal gradients in Inner Mongolia steppe. Belowground sampleswere collected by soil core method and belowground productivity was determined by ingrowth-bag method,and we recollected27bags. Meantime, the data of soil environmental factors were obtained by experimentsand climate information in sample sites was extracted with climate data of GIS technology and many years.Then the impacts of temperature, precipitation and soil factors on biomass, below-aboveground biomass ratioand belowground productivity were discussed by linear regression analysis. And then structural equationmodels were built to clarify the direct and indirect effect of environmental factors. The results show:（1） In general, the relationship of the species diversity index and belowground biomass were unimodal.The species diversity index and belowground biomass were negatively related in typical steppe and positivelyrelated in desert steppe. In typical steppe, the relationship weren’t clear, but were single-peaked in typicalsteppe, which were dominated with Stipa grandis and L. chinensis.（2） The aboveground biomass, belowground biomass and total biomass decreased from meadow steppe totypical steppe and to desert steppe and differed significantly among three grassland types. Butbelow-aboveground biomass ratio didn’t differ significantly among three grassland types.（3） The distribution pattern of belowground biomass was inverted-pyramid. Belowground biomass weremainly limited by soil total nitrogen.content in0-10cm soil layer, and by soil pH value in10-30cm soil layer.（4） The responses of aboveground biomass and belowground biomass to mean annual temperature werenegative significantly and to mean annual precipitation and soil organic carbon and total nitrogen content werepositive significantly. B/A responded insignificantly to all environmental factors.（5） The mean belowground productivity was269.1g·m^-2·a^-1. The response of belowground productivity tomean annual precipitation was positive significantly and to mean annal temperature and soil pH value wasnegative significantly.（6） The impact of climate on soil factors was remarkable and there were also relationships among soilfactors. The effects of soil factors reflect indirect effect of climatic factors to some extent. Climatic factors,especially the variety of annual precipitation, were the main reason causing the differences of biomass andproductivity. Since the large diversity among community compositions and there were complex interactions amongenvironmental factors, the effect of each environmental factor on B/A might be limited, implying furtherthorough study need to focus on plants in physiological and synecological aspects.