Impacts of global climate changes on the water and heat factors in the Songnen Steppe The Scenarios in the Songnen Steppe Utilization of carbon sources by soil microbial communities of four plant functional groups in Songnen Steppe Influences of Flooding Disturbance on the Distribution Patterns of Three Grass Populations on the Songnen Steppe, Northeastern China Impacts of Climate Change on Soil Water Balance and Grassland Productivity in the Songnen Steppe