Soil Moisture Distribution Of Different Scale And Its Response To Rainfall In Loess Plateau Of Western Shanxi Province

Drought and soil erosion is an important limiting factor for the vegetation construction in the loess area, the reseach on soil mositure distribution can provide guidence and basis for water and soil conservation, ecological environment construction as well as water resources sustainable utilization. This paper chooses different landuse type sample, Artifical Robinia pseudoacacia forests (ARF) in different age and different vegetation types watershed in Caijiachuan as the research object, using the method of positioning soil moisture observation, through analysis of the difference and the change regularity on soil moistures, studied the distribution on different land sample and the inflection of rainfallon on soil moisture and runoff in different landuse watershe.the main conclusions are as follows:(1) It was shown that the order of total soil moisture in rainy season was argriculture land(AL)> waste grassland (WL)>Pinus tabuliformis forestland(PF)>Robinia pseudoacacia forestland(RF);In vertical direction, AL and WL shows dry in upon layers and wet in below, PF and RF and showed strong water deficit, RF mainly use the soil moisture in 20-200cm soil layer, and PF is mainly the use of soil moisture in 20-140cm soil layer. Runoff superimposition is obvious in WL and AL,as artifical forest has a significant ability of adjust the space allocation of water resouces.The order of degree of impact on the soil moisture was:land use>soil depth> slope position.(2) It was shown that the order of total soil moisture in rainy season was waste grassland>20a>15a>10a;Matured ARF has a significant regulation on the slope soil moisture distribution,10a ARF is in the locust vigorous growth period, soil mositure in deeper place soil can be used,15a ARF has a stable effect on soil moisture below 100cm depth; ARF cause a serious soil moisture deficit, with the increase of forest age, the soil moisture of 0-200cm soil profile is improved, but there’s no recover signs for200-400cm soil profile.(3) In dry years, the order of the average soil moisture is, early rainy season> middle of rainy season> end of rainy season. When the elative elevation from the channel bottom is obove 20m, soil moisture spatial distribution is largely affected by vegetation, while positions below 20m is dominanted by the slope position. Rainfall can cause different changes in soil moisture in different watershed, but the effect on spatial distribution pattern of soil moisture is tiny.(4)Natural vegetation restoration method can reduce surface runoff and shows a good water conservation function. Increasing the forest cover rate can reduce the consumption of surface evapotranspiration, and reduce the runoff coefficient. Watershed consumption is the main destination of water resources in watershed, the main destination of the water change is soil evaporation, vegetation transpiration, runoff and soil water storage. The soil moisture is higher within the watershed, the stronger ability of confluence and production flow it has.Soil moisture and base flow shows a close relationship, there’s a certain relationship between watershed runoff characteristics and soil physical properties like bulk density.