Abstract: A quantitative study on the relationships between the spatial distribution of major grassland species in 145 sampling plots in Yanhe River catchment and the 12 environmental factors extracted by GIS spatial analysis was conducted, and the geographic distribution of individual species with relations to environmental gradient was analyzed by using generalized additive model (GAM). The results showed that the main environmental factors affecting the spatial distribution of the grassland species were mean annual precipitation, mean annual air temperature, and evaporation, followed by seasonal fluctuation of air temperature, and slope position and grade. There existed close relationships between the major grassland species and the environment, and each species had its own specific environmental gradient space, with different responses to the environment factors. GAM could better depict the relationships between species spatial distribution and environment factors, and it was feasible to employ this model to explore the relationships between single species distribution and environment in a catchment scale.

Key words: Peanut, Early rice, Transpiration rate, Stomatal conductance, Water stress