Soil Moisture Dynamics Under Differewt Land Uses in Hilly and Gully Area on Loess Plateau

Based on data collected by random survey of soil moisture in loess hilly and gully region,the authors analyzed the soil moisture dynamics of different land uses.The study showed that land uses resulted in the differences of dynamic characteristics of soil moisture.The crop land and the apple-orchard land had the same dynamics variation.With the process of time,soil moisture increased gradually and then fell.The lands without human husbandry,such as forest,shrub and grass land had the different trend.The soil moisture reduced gradually with time.In rainy season,soil moisture appreciably increased,but its extent was not markedly.At the same time,land uses also made the dynamic characteristics of soil moisture profile different.The authors used standard deviation to separate the layer of the soil vertical moisture variation.The result indicated that the active moisture layer of farm land was markedly shallow.Land uses of different types made the variation coefficients and their variety different.Except for the 0—10 cm layer,the variation trend of different layers is accordant.As a whole,soil moisture reduced gradually month by month.The expiation of rainfall was impaired by vegetation transpiration and soil evaporation.