The Research of Artificial Forestland on Soil Water in the Semi-arid of the Loess Plateau

The condition of soil water of main forestation trees in semi-arid vegion on the Loess Plateau was studied,the results were as the following:(1) the soil moisture contents of forestland were low,near to the wilting humidity.In May 2002,soil moisture within 6m depth was 5.02%~5.12%,in May 2003,the soil moisture was 4.65%~6.35%.The influence on soil moisture only took place within 2m depth,in 1.8~4.0m layer,there was obvious soil desiccation,and the soil moisture was on the wiltin humidity.(2) the distribution of soil moisture in different forestlands and wastelands indicated that the existence of dried soil layer was a general common phenomenon in this region.The cause of this phenomenon was from the long-term deficit of soil moisture due to the special climate conditions in this region,not from the growth of forest trees.