Study on Dynamic Changes of Soil Water of Different Vegetation Types on the Loess Plateau of Western Shanxi Province

In 2005,adopt TDR carry on the soil humidity dynamic state research on 8 vegetative types at Caijiachun watersheld in west Shanxi Province.The result indicates that:in 2005,the characteristic of variety process of the average soil humidity in the range of 0～200 cm has small differences among the sites except farmland.During the growing season,different vegetations can be arranged in the high-to-low order of soil humidity as: farmland,Platycladus orientalis,secondary forest,Pinus tabulaeformis,orchard,Robinia pseudoacacia× Pinus tabulaeformis,Robinia pseudoacacia× Platycladus orientalis,grassland and Robinia pseudoacacia.As to seasonal variation,divide the growing season into three periods: lessen period,stable period and compensatory period.Compared with orchard,farmland,grassland and secondary forest,artificial forest has stronger effect in improving soil moisture condition.In diurnal changes,soil moisture content of all of the sites are affected by rainfall and distribution.According to soil humidity vertical variation,the soil profile can be divided into three layers: weak utilization layer,utilization layer and regulating layer.As to the soil moisture content variety trend,Farmland,secondary forest,Pinus tabulaeformis,Platycladus orientalis,pseudoacacia× Platycladus orientalis,grassland and orchard are increment pattern;Robinia pseudoacacia and Robinia pseudoacacia× Pinus tabulaeformis,Robinia are decline pattern.