Changes in stress within grassland ecosystems in the three counties of the source regions of the Yangtze and Yellow Rivers

Abstract

Based on a database of more than 40 years of second production process and energy flow records for Maduo, Qumalai and Yushu counties, a dynamic model of the stress within grassland ecosys- tems was established using a nonlinear regression method for this source regions of the Yangtze and Yel- low Rivers. The results show that dynamic curves of stress within grassland ecosystems in the three coun- ties were in the shape of an inverted "U" during the period 1965-2007. It also revealed that the variation in actual amount of livestock inventories reflected the general trends of the stress within the grassland eco- systems in the source regions, although there were many other factors for the increase or reduction in grassland ecosystem stress.