Moisture Factor Dynamics And Its Impact On Aboveground Biomass In Stipa Klemenzii Steppe

Water is the significant factor in controlling the structure and function of terrestrial ecosystem, precipitation and soil moisture are the main limiting factors of aboveground biomass, especially in the grassland region. Desert steppe is not only an important grassland ecosystem type but also one of the most important grassland resources types in Inner Mongolia. However, due to the global climate change and the irrational use of grassland resources, desert grassland degradation is becoming more serious, desertification trend is growing. The structure and function of desert steppe ecosystem as well as its response to moisture factor is drawing widespread attentions.In this study, taking Stipa klemenzii steppe as example, combined with soil moisture content (15cm underground) and rainfall monitored during the past contiuous four years and the rainfall data in recent50 years from the nearby meteorological station in desert steppe, soil moisture dynamic as well as the response to rainfall were explored and the response of aboveground biomass dynamic characteristic of community and functional groups to moisture factor was analysised and discussed based on positioning survey of the community and the functional group aboveground biomass. Our results showed that:1. The dynamic of soil moisture in desert steppe shows two pattern, Unimodal or bimodal, it is mainly effected by rainfall distribution pattern.2. Soil moisture reflected more rapid change with the greater rainfall, or the greater rainfall intensity, or the higher soil moisture content before rainfall.There is no response of soil moisture(15cm underground) when rainfall is under5.0mm. However, the soil moisture increased significantly when rainfall is more than18.0mm.3. The aboveground biomass is low in desert steppe, there is high yearly variability in the aboveground biomass distribution pattern. The perennial grasses is a major part of the region community aboveground biomass. However, the contribution rate of perennial grasses to community biomass shows gradually reduced trend in the growing season, on the contrary the contribution rate of other functional groups to community biomass shows continuous increased trend.4. In study area, the community aboveground biomass strongly correlated with both mean soil moisture content in the previous two months or growing season and cumulative rainfall in growing season, it was negatively correlated to cumulative rainfall in the previous two months. No matter in growing season or the previous two months, the aboveground biomass of perennial grasses strongly correlated with mean soil moisture content, it was negatively correlated to cumulative rainfall; the aboveground biomass of shrubs or semi-shurbs and perennial forbs strongly correlated with cumulative rainfall, and they were negatively correlated to mean soil moisture content.