Pinus tabulaeformis carr. and Hippophae rhamnoides are widely planted in the low mountainous upland and loess plateau, and are main species for afforestation in the semiarid region. In order to expound their roles in controlling serious soil and water loss and the mechanism of role, a study on the hydro-ecological effects of the stands was carried out in the period from 2002 to 2004, using the method of runoff plot set up in different stands and soil physical and chemical analyses.
The experimental stands are located in the low mountainous upland of western Liaoning Province, where the annual average air temperature is 5.4～8.7℃, the annual precipitation is 450～580mm, of which in June averages 238.9mm, the annual average humidity is 38%～82%. Vegetation cover is 28% of entire land area. The age of Pinus tabulaeformis Carr.stand is 28 year old, and its density is 2825 tree/hm², and forest crown coverage is 0.75; while those Hippophae rhamnoides stand is 11 year old, 8950 tree/hm2, 0.90, respectively.
The results showed that the intercepting rates of canopy in Pinus tabulaeformis carr. and Hippophae rhamnoides stand were 23.08% and 32.28%. The litter intercepting rate averaged 14.17% in Pinus tabulaeformis carr. and 20.8% in Hippophae rhamnoides stands, respectively. The runoff depths were 2.516mm and 0.893mm in Pinus tabulaeformis carr. and Hippophae rhamnoides stands while erosion amounts 15.57 t km^-2 and 0.76 t km^-2, respectively. Under the comprehensive action of the artificial stands, the runoff depth and erosion amount from woodland were, respectively, 1/20 and 1/50 of that from wasteland, which indicated the great hydro-ecological functions of Pinus tabulaeformis carr. and Hippophae rhamnoides forests.
Litter and died roots may be decomposed into organic matter and nutrient substances with the help of microbe; thus will be distinctly improved the physical and chemical properties of its soil after death. In comparison with wasteland, the bulk density of soil decreased in woodland, while the content of organic matter, total N, total K and available K significantly increased. The physical properties of soil in woodland, such as total porosity, non-capillary porosity, saturated moisture content, non-capillary water-holding capacity etc., were distinctly higher in surface soil (0～20 cm) than those of soil at the depth of 20～40 cm. There was no significant difference in pH、total P and available P among different land types or different soil depth. The non-capillary water-holding capacities in Pinus tabulaeformis carr. and Hippophae rhamnoides stands were 182.1% and 275.9% times in wasteland, respectively.