Spatiotemporal Variability of Soil Moisture under Different Agroforestry Landscape in Jinghe River

摘要

Measured the cover soil water content in soil layer 0～30 cm of different agroforestry landscape types in Jinghe river with TDR, the landscape types including sloping cropland, apple orchard, apple-clover system, land under forest and grass changed from grain crop and black locust forest. Analyze the distribution characteristic and spatiotemporal variability of the cover soil water. The result showed that the soil water has renewed in a certain extent after a rain period in 1.5 m soil profile; the soil water content is gradually increased from the top of to the bottom of the slope under the affection of the slope location and plant category. The theory model of semivariogram for cover soil water content before rain season and after season, the value of nugget is changed no obviously, and they are 0.25 and 0.30; ranges is 99.7 m and 87.6 m. And the results indicated that soil moisture exhibited high fractal dimensions and clear spatial autocorrelation. The fractal dimensions are 1.71 and 1.74 variogram is main autocorrelation. During rain season the theory semivariogram model is linear, the spatiotemporal variability of soil water content becomes higher with the increase in distance, and its fractal dimension is 1.40. Jing river is a major tributary of the he middle reaches of the Yellow River, a total length of 483 km, the basin area of 45421 km~2, of which water and soil loss area of 33220 km~2, accounting for 73.1% of the total area. According to the landform types in the basin can be divided into Loess Hilly and gully region, the gully area of the Loess Plateau hilly region, soil, loess hilly area and loess terrace area. The hilly and gully area of Loess Plateau and gully region of loess plateau area occupies the entire basin 81% (Guo Dongbin, 1999). Most of the farmland without irrigation, agriculture and animal husbandry to obtain natural precipitation becomes the main water source. Land use and land topography is the impact of spatial and temporal distribution of soil moisture is the important factor (Crave, 1997), in the area of soil moisture is not only the process of soil erosion (Jiang Dingsheng, 1997), plant growth (Yang Wenzhi, 1992) and vegetation restoration (Zhu Zhicheng, 1993) and the main influence factors of land, is an important index in the evaluation of (Fu Bojie, 1991). Due to the heterogeneity of the soil itself (Fu Bojie, 1991; Wu Qinxiao, 1998), at the same time as in the semiarid area of loess plateau gully slope position, under different planting patterns influence, will increase the spatial variability of soil moisture. The soil moisture spatial variability and its affecting factors made a lot of research (Li Yushan, 1990; Fu Bojie, 1999; Liu Mei, 1990; Wang Jun, 2000; Pan Chengzhong, 2003), of the slope soil water study is the main target of gentle slope land in or on a steep slope, woodland, and for the different land use patterns in spatial and temporal distribution of soil moisture characteristics research. This study chooses the gully area of the Loess Plateau Watershed with different land use way, on the different position of slope, vegetation type under the influence of surface soil moisture content determination, to study the temporal and spatial distribution characteristics, designed for gully region of Loess Plateau Watershed of agricultural production, the restoration of vegetation and rational use of land to provide some guiding significance, to for a period of adaptation in Jinghe River basin economy and protection of ecological environment coordinated development's needs, for the construction of agroforestry landscape optimization configuration model provides a scientific basis.