Soil desiccation in deep soil layers under different vegetation types in the semi-arid loess hilly region
半干旱黄土丘陵区人工植被深层土壤干化效应

Artificial vegetation restoration as an effective way to control serious soil erosion and improve environment conditions has taken several positive environmental effects.However,serious soil desiccation as one of negative effects also appears associated with artificial vegetation restoration lack of scientific guidance,especially in deep soil layers.To recover the fragile ecosystem of the Loess Plateau and maintain sustainable development of this region,proper artificial vegetation types should be selected based on local soil water conditions.However,methods to quantitatively evaluate soil water effect based on local rainfall and soil water conditions is urgently needed to improve,which is one of the top priorities in current research.To quantitatively evaluate the soil desiccation degree in vegetation types,14 vegetation types were selected to analyze the eco-hydrological effect in deep soil layers in the typical semi-arid loess hilly region.Compared Soil Water Deficit Index(CSWDI) and Plot Compared Soil Water Deficit Index(PCSWDI) were induced to quantitatively analyze the soil water deficit in different vegetation types.The research showed that high-density artificial vegetation was the main reason of deep soil desiccation.Soil water contents in all vegetation types increased with soil depth except abandoned land and farmland,and had a significant linear relationship with soil depth.The degree of soil water deficit of different vegetation types was Pinus tabulaeformis forestland>Pinus tabulaeformis and Platycladus orientalis mixed forestland>Armeniaca sibirica forestland>Caragana korshinskii shrubland>Medicago sativa grassland>Platycladus orientalis forestland>Amygdalus davidiana shurbland>Armeniaca sibirica and Platycladus orientalis mixed forestland>Populus simonii forestland>Populus simonii and Platycladus orientalis mixed forestland.Soil desiccation various in soil profile cause for transpiration,root system characteristics and tillage management between different vegetation types.Solanum Tuberosum farmland,Zea mays farmland and abandoned land had no soil water deification compared with natural grassland.Comparisons of soil water contents in mixed forestland and pure broadleaved forestland showed that soil water condition in mixed forestland was better than that in pure broadleaved forestland.Results of this study also indicated that the CSWDI and PCSWDI were capable of reflecting conditions of soil water deficit in different soil layers and plots.They could be used as quantitative indices for soil water deficit analysis under different vegetation covers.