Availability Of Soil Water For Steep Slope Vegetation Restoration In Semi-arid Loess Region Of North Shaanxi

The influence of available water content to vegetation restoration and reconstruction is remarkable.In order to explore the characteristics of available water in surface soils on steep road-slopes,the study which choose steep road-slopes(>45°)and five micro-topography in loess area of north Shaanxi as research object used centrifuge method to fit soil moisture characteristic curves to obtain field water holding capacity and wilting coefficient,and used them to study on saturation of soil available water of 0?60 cm of steep road-slope with different slope aspects,slope grades and formation time.The variation characteristics of saturation of soil available water of 5 kinds of micro-topography and its original slope were analyzed,and the response of vegetation community characteristic index to saturation of soil available water was studied based on Mann-Kendall trend test and wavelet analysis.The following conclusions were drawn.(1)The phenomenon of topsoil desiccation exists in the steep road-slope in the loess region of Northern Shaanxi.Even during the rainy season,there is still non-available water layer on the bare and steep road-slope,and the saturation of available water is zero.Slope aspect is an important factor in the formation of topsoil non-available water layer in the steep slope.With the increase of the slope gradient and the prolongation of the formation time of the slope,the thickness of the non-available water layer will increase.(2)At 0?60cm soil depth range,In terms of saturation of available soil water,the different landform units can be ranked in the Descending order of undisturbed slope,collapse,shallow gully,gully,platform and scarp.The saturation of soil available water of gully and collapse increased significantly;the saturation of soil available water of scarp also increased with a non-significant trend;the saturation of soil available water of shallow gully,platform and undisturbed slope showed a downward trend,but the trend was not significant.(3)The change cycle of soil available water saturation in different micro-topography is different.Scarp,collapse and platform had same main cycle which is 22mon.The main cycle of shallow gully,gully and undisturbed slope were 23mon,21mon and 28mon,respectively.(4)Margalef richness index,Shannon-Wiener diversity index,Simpson diversity index and Alatalo evenness index were positively correlated with saturation of available soil water.The highest correlation was found between Simpson diversity index and saturation of available soil water.