Effects of Land Use On Soil Water in the Loess Plateau, China.

In water-limited ecosystems, large-scale changes in vegetation are an important component of global change. One example of these vegetation changes is the ¡°Grain to Green¡± program conducted by Chinese government in the Loess Plateau. Many hectares of steep farmland were converted to grass land or forest, which has potential large-scale ramifications for both water and carbon cycling. Soil water dynamics and soil respiration of different land use patterns were studied by measuring and simulating data in the Loess Plateau of China. Two years of data in four land use patterns were analyzed and the Hydrus-1D model was used to simulate root water uptake driven by evapotranspiration and the impact on deeper soil water content dynamics. Results showed the evapotranspiration from four vegetation types exceeded precipitation with distinct differences in soil water content and water balance calculations among species. There were also significant differences in the effects of precipitation on soil water dynamics. Water uptake by alfalfa extended to deep soil layers where other plant roots (grass) were absent during the two-year study period. Detailed understanding of the water balance is needed to design and manage vegetation restoration in the Loess Plateau. Sustainable vegetation should have high water use efficiency and minimal reliance on deep soil water storage.