Climate Change During The Past 50 Years And Its Impact On The Production Ability In Inner Mongolia Grassland

The climate is the most primary factor that determines the vegetation types and species distribution. With the long effect of climate such as rainfall, temperature and sun radialization, there were Meadow Steppe, Typical grassland and Desert Steppe distributed in the Inner Mongolia from East to West. Based on the measurements of aboveground productivity, and changes of precipitation and temperature during the past 50 years in the three kinds of grassland region, this paper attempted to analyzes the effects of climatic changes on grassland degradation in Inner Mongolia region. The main conclusions are listed in below:1. The annual mean air temperature and the mean air temperature in four seasons increased in the past 50 years from East to West in the Inner Mongolia grassland region, The annual average temperature increased 0～0.45℃(10a)^-1, the range of increase was 12.5%, 15.7% and 13.6%, respectively in the Meadow Steppe, Typical grassland and Desert Steppe. The extreme highest air temperature increased most greatly in winter while the extreme lowest air temperature only change slightly.The distributed trend of precipitation was regionally different in the past 50 years. The precipitation in Meadow Steppe increased from 1960 to 1980, thereafter decreased distinctly after 1990, the range of decreased was 6.6 mm (10a)^-1 and the precipitation mainly decreased in spring. The patterns of precipitation in the Typical grassland and Desert Steppe were characterized by curved lines, there were a small peak in the middle of 1950s, 1970s, and 1990 and the precipitation fluctuated 2.5-5.8 mm (10a)^-1. The annual precipitation in Desert Steppe varied slightly (0.8-2.2 mm. 10a^-1). The moisture index (K) which combined water and heat kept constantly though observed increase of air temperature in the three type of grassland.2. The annual productivity in the Inner Mongolia steppe varied largely and was 150-250,160-200,90-105 g.m^-2, respectively in the Meadow Steppe, Typical grassland and Desert Steppe.With the effects of precipitation and temperature, the observed values of aboveground biomass fluctuated greatly in the Meadow Steppe and Typical grassland while continued to increase in the Desert Steppe which more depended on precipitation. The relationship between grassland productivity and temperature and precipitation showed obvious spatial variation.According to our results, Holdridge's life zones system has certain limitation in estimating theproductivity of Inner Mongolia grassland, more work was needed for the emendation of this model.Our results suggested that the land reclamation and use irrationally is the main reasons of grassland degradation, the climate change may accelerate the process.