Survival Capability Analysis of Four Kinds of Artificial Forests in Loess Plateau

The continuous dry climate has been threatening the survival of the artificial forests in the Loess plateau in resent years. Some of the branches on the treetops have perished or the whole woods have died of drought. This study has chosen the lands of Pinus tabulaeformis, Platycladus orientalis, Ulmas pumila, Caragana microphylla, grazing and farmland in the loess hilly and gully area of Suide county, Sannxi province, and measured the soil water contents from 0~9.9 m on soil profiles to test the survival ability of different trees. The results showed that the critical survival soil water content for Pinus tabulaeformis and Ulmas pumila are between 4.5%~5.2% and 5.2%~5.8% respectively, and the corresponding relative water moisture are 27.6%~31.9% and 31.9%~35.6% respectively. The soil moisture of Platycladus orientalis and Caragana microphylla are 4.3% and 4.2% respectively, and the corresponding relative water moisture are 26.4% and 25.8%, but both were still alive. 