Simulation Of Soil Moisture Movement Under Different Land Use Types In Loess Hilly Area

The natural environment of gully region of loess plateau is fragile,water loss and soil erosion is serious.The research on slope surface water movement law is a popular research field in the fields of soil science,water literature and ecology.In view of that location monitor and numerical simulation of the runoff cell based on the present study,the law of the migration of soil moisture in bare land,grassland and woodland was study using the methods of correlation analysis,variance analysis,wavelet analysis,redundancy analysis,etc.,and analyzed the spatio-temporal distribution characteristic of soil moisture in different land use types,and determined the response relation of soil moisture to environmental factors in different land use types,and provided an important basis for the dynamic and slope surface water balance of soil moisture,which provided the land water management of slope and the utilization of land.The main conclusions are as follows:(1)Soil moisture and space-time characteristics in different soil layers(within 100 cm)of different land use types were studied.Soil moisture of 0?50cm on the upper layer is affected by the seasonal transformation to a different degree,where 0?10cm is the water-steam exchanging active layer.The average value of soil moisture content of grassland and woodland is relatively close,and the soil moisture of woodland is more stable over the seasons than the grassland,and the more the soil water content in the middle part of the slope is nearer to slope.(2)The soil water content of the bare,grassland and woodland is the periodic variation of the first main period at a time scale of 200 days on the day scale,due to the periodic variation in soil moisture due to seasonal climate change;The thicker the soil layer,the smaller the water content of the soil,and the tendency to flatten;In the 0?100cm range,the water content of each soil layer in the forest land is higher than that of the grassland,and the spatial variation is more stable;In spatial distribution,the moisture content of the soil exhibits strong spatial heterogeneity.(3)The main meteorological and soil factors affecting the water distribution of soil in slope surface were determined.According to the RDA sequence analysis of meteorological factors and soil water content,air temperature,surface temperature and relative humidity are the most important factors influencing soil water content in bare soil.The maximum influence on grassland is water vapour pressure,and the forest land has the biggest influence on relative humidity and water vapour pressure due to the different vegetation coverage.According to the characteristic of soil physical and chemical properties,the bare land for the amelioration of soil bulk density,smallest largest woodland,bare soil water content increases with the increase of bulk density,grassland soil water content decreases with increasing bulk density,forest land has no obvious change trend;The soil porosity and bulk density results in contrast;It was found that that content of soil organic matter in profile soil was at least 2.8%?9.12%,and the organic matter content of the profile soil was the bare land,and the grassland was the most significant,and the water content of the open soil was negatively correlated with the content of the organic matter,and the organic matter content and soil water content of the grassland and the wood land had a positive relation in correlation.It was found that that soil wat content in the nude surface was negatively correlated with the content of the clay particle and the sand grain,and there was no obvious tendency for grassland and woodland to change.(4)soil moisture migration process of different land use types is revealed.It analyze that simulated mechanism of HYDRUS-2d model and the principle of soil wat movement,and optimizes the parameters of HYDRUS-2d model according to the actual monitor data.According to the measured soil water content and simulate the Nash efficiency coefficient between soil water content,root mean square error,decision coefficient of the three indicators of HYDRUS-2d model simulation results were analyzed,and the results show that HYDRUS-2d model under the condition of the test on the soil moisture migration regularity of simulation precision is higher,soil water content of soil and shallow 0?50 cm simulation effect is best.The water consumption characteristics and moisture equilibrium of three types of bare land,grassland and forest land are quantified,and the soil water is replenished with rainfall without human disturbance,the water volume of the forest land is the largest,and the second place is the grassland,and the minimum is bare.Soil water content varies greatly among different land use types,and vegetation coverage is the main reason for water content difference.