Characteristic And Regulation Of Soil Moisture Under Typical Degraded Vegetation In Loess Covered Pisha Sandstone Area

Soil erosion is extremely serious in the middle reaches of the Yellow River,which has a negative impact on the ecological environment and safety of the lower reaches.Studying the dynamic response of soil moisture to rainfall in typical plots and the effects of different soil and water conservation measures on soil moisture in Pisha Sandstone areas are of great scientific significance for revealing the soil hydrological process in this area,and promoting the prevention and control of soil erosion and ecological restoration.At present,there is little research on the in-situ moisture dynamics and rainfall infiltration supplement process in the semi-arid Pisha Sandstone area.However,due to the difficulty of field tests,there is little research on the in-situ water dynamics and rainfall infiltration recharge process in the semi-arid Pisha Sandstone area.In this paper,soil plots of different cover types(Loess Covered Grassland,Loess Covered Seabuckthorn,Loess Covered Seabuckthorn with Stumping and Uncovered Grassland),and 3 different fish scale pit water retention measures(Fish Scale Pit,Grass Covered Fish Scale Pit and Grass Covered Fish Scale Pit+Infiltration Hole),through dynamic monitoring of the soil moisture distribution in the 0-160 cm profile,combined with the determination of the hydraulic properties of the undisturbed soil sample,the study characteristics of soil moisture under typical degraded vegetation in the Loess covered Pisha Sandstone area and the effect of different regulation measures on water retention.The following research results were obtained:1.Seabuckthorn has a better effect on soil improvement than grassland,which is mainly reflected in the increase of soil aeration pore,the increase of saturated hydraulic conductivity and the slight decrease of bulk density,and the difference is more obvious in 10-20 cm.The Loess covered layer has better soil hydraulic properties and soil pore structure than the Pisha Sandstone.It is mainly reflected in the increase of capillary porosity(40.89%)and the decrease of bulk density.Generally speaking,the water holding capacity of the Loess covered is significantly stronger than that of the Pisha Sandstone area.Due to the degradation of the soil structure,the sand accounts for a relatively high proportion of the surface Pisha Sandstone,and the water is difficult to maintain.After one year of stumping,the change of soil hydraulic properties was not significant.2.The existence of Loess-Pisha Sandstone layer hinders the infiltration of soil water.The presence of Loess covered layer and seabuckthorn planting can significantly increase the infiltration of soil water in the process of rainfall.In the process of rainfall,the response of covered grassland to rainfall was 18.46% higher than that of bare grassland,and the water holding capacity of redistribution was 127.89% higher.The response of Seabuckthorn to rainfall was 114.16% higher than that of grassland,and the water holding capacity during redistribution was 68.45% higher.The long-term monitoring results show that the Loess covered layer significantly improves the water holding capacity of the soil,and effectively improves the soil moisture status of the Pisha Sandstone area.The average water storage of the Loess covered layer increased by 31.77%,which was more obvious in the wet period;in the Pisha Sandstone layer,the Loess covered layer increased the water content of the lower layer Pisha Sandstone by 8.68%,which was more obvious in the dry period,indicating that the existence of the interface aquiclude not only blocked the water infiltration,but also blocked the upward loss of the lower layer water,which slightly increased the water storage of the lower layer in the dry period.Seabuckthorn increased the capacity of soil water storage and water conservation,and the average water storage of Loess covered was 4.45% higher,mainly in the wet period.Seabuckthorn had a greater advantage in water infiltration and soil water conservation after rainfall.The water can hardly infiltrate into the soil of exposed Pisha sandstone,which is easy to form runoff and aggravate soil erosion.of exposed arsenic sandstone,which is easy to form runoff and aggravate soil erosion.3.The rainfall mainly affected the water content of the overlying soil layer,but had little effect on the water content of the deeper Pisha Sandstone.Grass covering increased infiltration of soil water in fish scale pit during rainfall.In the process of rainfall with grass cover,the infiltration of soil water in fish scale pit increased by 24.53% compared with that without grass cover,and the infiltration hole did not increase the total infiltration,but increased the water supply depth brought by rainfall,which increased the soil water content of 80-100 cm by 57.46%.The results of one-year monitoring show that the soil moisture change is more intense in the upper Loess,and the total soil water storage is Grass Covered Fish Scale Pit+Infiltration Hole > Grass Covered Fish Scale Pit > Fish Scale Pit.Grass covering measures can buffer the change of soil moisture in different seasons,and effectively enhance the soil moisture conservation capacity.The soil moisture increased by 7.53% in summer and 11.38% in winter.The infiltration hole can effectively improve the soil water and supply depth of the covered Pisha Sandstone area.The 70 cm infiltration hole mainly supplies the soil water below 80 cm soil layer.4.In the process of rainfall,the difference brought by flat stubble is not obvious.In the process of redistribution,because of the difference of canopy cover,the surface soil moisture in flat stubble area decreases faster.The results of one-year monitoring showed that the total soil water storage of stumping was higher than that of non stumping.Generally speaking,one year of stumping had little effect on soil moisture,only slightly increased on the soil moisture of Loess layer.