Response Of Soil Moisture Content To Returning Farmland To Forest (Grass) In Loess Plateau

The soil erosion in the Loess Plateau is serious and the ecological environment is very fragile.In order to improve the ecological environment of the Loess Plateau,China implemented the project of returning farmland to forest and grass in 1999,soil moisture in the Loess Plateau is the main factor restricting the construction of vegetation,and the cultivation of returning farmland vegetation has a great influence on the change of soil moisture.In recent years,many scholars have studied the impact of the project of returning farmland to forest on soil moisture in different areas of the Loess Plateau.However,most studies only focus on the influence of a certain region or a certain factor on soil moisture.In order to study the effect of returning farmland to forest and grassland on soil moisture in a more comprehensive study,based on the data of many scholars,this paper uses the method of integrated analysis to analyze the soil area of the Loess Plateau,and integrates the soil moisture data of the degraded vegetation from each area.From the aspects of rainfall,vegetation type,vegetation age and vegetation density,the effects of returning farmland to soil moisture on the Loess Plateau were analyzed.The main conclusions of this study are as follows:1.The average annual rainfall in the Loess Plateau is stable,decreasing from south to north,and the unevenness of rainfall is arid area> semi-arid area> semi-humid area.In the space,the soil water content decreased from south to north,Which is consistent with the spatial distribution of average annual rainfall.From a time perspective,the relationship between soil water content is expressed as October> June> September> July> August.2.The relationship between soil water content of different vegetation types is farmland> wasteland> alfalfa grassland> shrub and arbor forest in semi-arid and sub-humid areas.Therefore,in the process of returning farmland to forest should be based on local rainfall conditions to select the appropriate retreat vegetation.3.In the semi-arid and semi-humid areas of the Loess Plateau,soil water content of returning farmland vegetation decreased with the increase of planting period.Therefore,the vegetation planting period should be controlled during the process of returning farmland to avoid the serious consumption of soil moisture due to the high vegetation planting period.4.The change of planting density in semi-arid and sub-humid lands showed the same regularity,that is,the soil water content decreased with the increase of planting density.This is due to the high density of vegetation to grow more water,In the soil layer of roots than low-density vegetation to absorb more soil moisture,resulting in reduced soil moisture.Therefore,in the process of returning farmland to forest should be based on the actual local climate conditions to choose a reasonable density,rather than blind pursuit of high density,high coverage.