Hydro-ecological effects of artificial Pinus tabulaeformis carr. and Hippophae rhamnoides woods in the low mountainous upland of Western Liaoning Province, China

Pinus tabulaeformis carr. and Hippophae rhamnoides are widely planted in the low mountainous upland and loess plateau and are the main species for afforestation in the semiarid region. To expound their roles in controlling severe soil and water losses and the mechanism of their roles, a study on the hydro-ecological effects of the woods was carried out during 2002–2004, using the runoff plot method set up in different woods and conducting a physical and chemical analyses of the soil. The experimental woods are located in the low mountainous upland of Western Liaoning Province, China where the annual average air temperature is 5.4–8.7°C, the annual precipitation is 450–580 mm, of which June averages 238.9 mm, and the annual average humidity is 38%–82%. The coverage rate of vegetation is 28%. The age of Pinus tabulaeformis carr. is 28 a, its distribution density is 2825 ind.·hm2, and its coverage rate is 0.75, while those of Hippophae rhamnoides are 11a, 8950 ind.·hm2 and 0.90, respectively. The results showed that the intercepting rates of canopy in Pinus tabulaeformis carr. and Hippophae rhamnoides were 23.08% and 32.28%. The litter intercepting rate averaged 14.17% in the Pinus tabulaeformis carr. woods and 20.8% in the Hippophae rhamnoides woods, respectively. The runoff depths in Pinus tabulaeformis carr. and Hippophae rhamnoides were 2.516 mm and 0.893 mm, while erosion amounts were 15.57 t·km−2 and 0.76 t·km−2, respectively. Under the comprehensive action in the artificial woods, the runoff depth and erosion amount from the woodland were 1/20 and 1/50 of those from the wasteland, respectively, which indicated the immense hydro-ecological functions of Pinus tabulaeformis carr. and Hippophae rhamnoides woods Litter and dead roots would decompose into organic matter and nutrient substances with the help of microbes, and would thus distinctly improve the physical and chemical properties of the soil. In comparison with the wasteland, the bulk density of soil decreased in the woodland, while the content of organic matter, total N, total K, and available K significantly increased. The physical properties of soil in the woodland, such as total porosity, noncapillary porosity, saturated moisture content, noncapillary water-holding capacity, were distinctly higher in surface soil (0–20 cm) than those in the soil at the depth of 20–40 cm. There was no significant difference of pH, total P, and available P among different land types or at different soil depths. The noncapillary water-holding capacities in Pinus tabulaeformis carr. and Hippophae rhamnoides were 182.1% and 275.9% times those of wasteland, respectively.