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 watershed in west Shanxi province, including seasonal variation and soil humidity vertical variation. In the modern soil moisture dynamics researches, the methods of dividing soil moisture profile and soil moisture variation season have no rigorous mathematical theory supports. The author resolves the problem by the Sequential Cluster method.The growing season is divided into three periods: lessen period, stable period and compensatory period. In general, the season variation is controlled by the environment; the different vegetation affected by the environment has different appearance and the vegetation with the different density enter the stable period in different time.The different vegetation has different soil moisture profile. The type of the soil moisture profile, the trend of the Platycladus orientalis, secondary forest, Pinus tabulaeformis is increment, and the Robinia pseudoacacia is decline pattern. The soil moisture profiles are divided into three layers: utilization layer, weak utilization layer, regulation layer. The result corresponds to the results of the researching on the biomass distribution of the total roots and the absorbing roots , so it meets the ecophysiological characters of the vegetation It indicates the rationality of applying Fisher's law to the deciding the depth of boundary layer and the total of the profile going to be divided.