Vegetation pattern determines the soil moisture dynamics in re-vegetation watershed in semi-arid regions
Soil moisture in fundamental to ecosystem sustainability in semi-arid regions, and characterizing the soil moisture dynamics to vegetation restoration is important for assessing the sustainability of vegetation restoration. Along with the large-scale ecological restoration in the Chinese Loess Plateau, identifying the ecohydrological response to human-introduced vegetation restoration has become an important issue in current research. In this study, we want to find the relation between vegetation pattern and soil moisture content, and to elucidate the response of spatial and temporal dynamics of soil moisture to human-introduced vegetation restoration. The soil moisture data in depth of 0-5 m was obtained by field observation and geostatistical method in two neighboring re-vegetation watersheds. The spatial and temporal dynamics of soil moisture were analyzed and compared between different vegetation types, transects, and watersheds.
The soil moisture was drastically decreased after vegetation restoration (in lands covered with pasture grass, shrub, and forest) and became temporally stable when compared with lands covered with crops and native grasses. No significant differences in soil moisture content were found between different introduced vegetation types in layers below 2 m. The high planting density is considered as the main cause of severe soil moisture deficit on a long-term temporal scale. The analysis of differences in soil moisture for different vegetation patterns indicated that the vegetation had significant influence on soil moisture spatial and temporal variability. Vegetation structure determined the soil moisture content and its spatial-temporal variation. Vegetation restoration with introduced plants diminished the spatial heterogeneity of soil moisture and induced temporally stable soil desiccation at the watershed scale. The improvement of vegetation management was suggested to improve the water management and maintain the sustainability of vegetation restoration.