Regional climate change and vegetation-water relations in Inner Mongolia lessons learned within the NASA Project 'Effects of land use change on the energy and water balance of the semi-arid region of Inner Mongolia, China'

Climate change in semi-arid areas can significantly affect the seasonal water cycle and increase the stress on vegetation and ecosystems that provide the basis for human livelihood. Climate change and water-vegetation interaction under the effects of land use/cover (LULC) was investigated in Inner Mongolia (IM), China. Climate records, data of micrometeorological water and energy fluxes and remote sensing products were used to examine the different phenomena and processes at various scales. Firstly, I evaluated the changes in the mean and extreme climate conditions at local, biome and regional scales based on long-term meteorological data and by means of the spatial interpolation method. Secondly, I examined how changes in LULC affected evapotranspiration (ET), soil water dynamics and their interactions in six semi-arid ecosystems. The investigation was based on the data from six eddy-covariance (EC) flux towers, which represented three paired sites (cropland vs. natural grassland, grazing grassland vs. natural grassland and poplar plantation vs. natural shrubland). Thirdly, the relationship between surface soil moisture and vegetation was examined at a large spatial scale by using the remote sensing products.;The major findings of this study were: (1) both the mean and extreme climate conditions pointed toward a drying and warming trend in IM, with more pronounced changes occurring in the grassland and desert biomes than in the forest biome, likely due to different intensities of human disturbances within the different biomes; (2) it is known that land surface properties play an important role for climate change. This study found that cultivation and grazing tended to decrease ET through shortening the period of plant growth and the restriction of the volumetric water content (VWC) as compared to the native grassland. The relative contribution of soil water storage (DeltaS) to ET was significantly correlated to the root biomass density in the upper 50 cm of soil; (3) the surface soil moisture and vegetation indices showed different relationships in the grassland, shrubland and cropland, based on remote sensing products of AMSR (Advanced Microwave Scanning Radiometer) and MODIS (Moderate-resolution Imaging Spectroradiometer). Finally, empirical models were tested to predict Ms using MODIS indices. These models showed plausible results and important insight to estimate finer-resolution Ms at a large spatial scale.