The Water/thermal Condition Dynamics And Its Impact On Vegetation Coverage In Ujimqin Grassland

In terrestrial ecosystems, soil, atmosphere and water elements connection through vegetation, heat, water and its distribution pattern determines the regional vegetation type on the earth, the change of vegetation can reflect the change of climate. Study the spatial temporal distribution of water thermal dynamic change and the corresponding changes of vegetation and the correlation between vegetation dynamics and hydro-thermal conditions is of great significance to forecast the ecological environment change trend in the study area.Taking Ujimqin grassland as the study area, with 2000-2013 years meteorological data and MODIS products as the main data sources, using time series analysis, trend calculation, correlation analysis and GIS spatial analysis for the research methods. Subsequently, the spatial temporal changes of growing season NDVI in Ujimqin grassland were analyzed and its relationship with precipitation, temperature and ET was also examined, the results indicated that:1. The hydrothermal interannual variation indicates that, the precipitation and ET in the study area was increased significantly at a rate of 95.7mm/10 a and 21.7mm/10 a. While the air temperature was decreased with a rate of 0.497 ℃ /10 a. In recently 15 years, Ujimqin grassland has a relative humidification trend in climate change.2. In 2000-2013, in Ujimqin grassland growing season the precipitation, temperature and ET of April are declining, May to September the precipitation and evaporation were increased, while the temperature in May and June have a upwards trend and other months have a downward trend, the temperature decline in July is the largest.3. Ujimqin grassland vegetation coverage in growing season increase with a rate of 0.05/10 a. Among them, the vegetation coverage showed a trend of decrease in April, during May to October the NDVI has increasing trend.4. NDVI value increases with temperature rise in March, high temperature is helpful to the growth of vegetation germination, especially important for the growth of vegetation; other times the temperature of NDVI value is negatively related to the vegetation growth, July is the most obvious negative correlation by temperature. Vegetation growth affected by rainfall during the month of April to June, July and August NDVI value was significantly positively related to the June’s precipitation, vegetation growth of precipitation change has certain hysteresis, but negatively correlated with NDVI and monthly precipitation in August, is due to reach maximum vegetation grew in August, excessive rainfall could cause flooding and affect the growth of vegetation. The Precipitation and temperature on the effect of vegetation NDVI have a threshold, the impact on vegetation has both promote and diminished role.