| The Loess Plateau is the most serious soil erosion area in the world, and it is also the key area of soil and water conservation and ecological construction in China. Since the 1980s, the Chinese government had carried out a series of ecological construction projects in the Loess Plateau, which played a positive role in vegetation restoration and soil erosion controlling, and meanwhile changed the occurrence pattern and the variation of temporal and spatial of soil water. In this study, the wangmaogou small watershed in the loess hilly region was selected as the object. By means of using the theories of hydrology, soil and water conservation,geomorphology, ecology and environmental science and the methods of field investigation,location monitoring, mathematical statistics, spatial analysis and numerical simulation, the influences characteristics of temporal and spatial distribution of soil water resources and vegetation bearing capacity were analyzed systematically. Thereby, the consumption and compensation pattern of soil water under different ecological construction conditions were clarified. The results could provide scientific basis for ecological construction and utilization of soil water resources management in the Loess Plateau. According to the above research, The main conclusions are as follows::(1) The temporal and spatial cdistribution of soil water content, soil water resources and soil water resources deficitUnder different ecological construction conditions, the average soil water content in soil layer 0-180cm were as followed: dam land> terracesd field > grassland > forest land. The soil water resources of the terraced field, forest and grassland decreased with the increase of soil layer, whereas the soil water resources of the dam land increased with the increase of soil layer.Except dam land, the soil water under different ecological construction conditions were in deficit state after the rainy season. The variation and the coefficient of variation of soil water resources decreased with the increase of soil layer in the soil vertical section.(2) Time stability of soil water contentThe average soil water content in the 8 soil layers of terraced field, forest land and dam land showed three kinds of spatial patterns: gradually increased in 0-60 cm, gradually decreased in 60-120 cm, and gradually increased in 120-160 cm. While the spatial patterns of dam land appeared as: gradually decreased in 0-60 cm, gradually stabilized in 60-120 cm, and gradually increased in 120-160 cm. The lowest soil water content was at soil layer 0-20 cm in the terraced field and forest land and was at soil layer 40-60 cm in dam land. The representative position of soil water content under different ecological construction conditions changed with the depth of soil. The soil water content of the best representative point of diffenrent soil layers under different ecological construction conditions could be used to accurately estimate the average soil water content of certain soil layer of each point in the watershed. Under different ecological construction conditions, the soil water content and the best representative point location of the soil water content in each layer were significantly different.(3) The vegetation bearing capacity of soil waterBased on the quantitative estimation of vegetation bearing capacity of soil water, the water conversion efficiency of different different ecological construction conditions were as followed:Under the ordinary production level and midium water supply, dam land (761g/m2· a) > terraces(654g/m2·a) > grassland (620g/m2·a) > woodland(506g/m2 a); While under the maximum production level and adequate water supply, dam land (893g/m2·a) > grassland (820g/m2·a) >terraces (515g/m2·a) >forest (482g/m2·a).(4) The effects of ecological construction conditions on consumption-compensation of soil waterDuring March 2015 to March 2016, soil available water content showed a trend of"rising-decreasing-stabilizing" in different ecological construction conditions. The consumption period was from March to July, and the compensation period was from August to November,followed by the stable period from December to next March. Under different ecological construction conditions, the average consumption and compensation of soil water of dam land,terraced fields, forest land and grassland were 0.33%, 0.27%, -0.26% and 1.88% (positive value corresponding to compensate of soil moisture, negative value corresponding consumption of soil moisture). |
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