Climate change tendency and grassland vegetation response during the growth season in Three-River Source Region

Climate change, climate suitablity change for grassland vegetation, and grassland response to climate change during the growth season are studied systematically by using meteorological data of temperature, precipitation, and length of sunlight from 1961 to 2007, NOAA/AVHRR NDVI from 1982 to 2006, and observations of grass height, biomass, and coverage in enclosed grassland from 1994 to 2006. Two models are developed to evaluate climate change and the climatic suitability of grassland vegetation growth. Average temperature, accumulative precipitation, and length of sunlight during the growth season increased from 1961 to 2007 at rates of 0.24A degrees C/10 yr, 2.32 mm/10 yr, and 2.81 h/10 yr, respectively. The increase rates of average temperature between April and May, and between June and August are 0.17 and 0.30A degrees C/10 yr; accumulative rainfall between April and May increased at a rate of 2.80 mm/10 yr, and accumulative rainfall between June and August decreased at a rate of 0.38 mm/10 yr; the increase rates of accumulative length of sunlight between April and May, and between June and August are 2.15 and 1.2 h/10 yr. The climatic suitability of grassland vegetation growth showed an increasing trend, and the increase rate between April and May is greater than that between June and August. Both NDVI observations from 1982 to 2006 and measurements of grass height, dry biomass, and coverage from 1994 to 2006 show that the climate change has resulted in an increase in plant productivity of the grassland in Three-River Source Region. If some protection measures are taken as soon as possible, the deteriorated grassland in Three-River Source Region can recover.