Seven afforestation densities of Picea crassifolia plantations were taken as the study object in this article in Anmentan small watershed

Datong County

Qinghai Province. Flooding method and ring knife method were used to determine water holding capacity of litter

herbaceous layer and 0-60 cm soil layer. This study quantified water conservation functions of Picea crassifolia plantation with different densities. The results showed that:(1) The maximum water holding capacities of litter varied from 1.97 m3/hm2 to 7.60 m3/hm2 for different afforestation densities. The afforestation density with the maximum litter water holding capacity was 1 725 plants/hm2

whereas the afforestation density of 2 300 plants/hm2 gave the minimum. The variation range of water holding capacities of understory herbaceous layer with different afforestation densities was as followed:1.97~7.17 m3/hm2. The maximum water holding capacity of understory herbaceous layer was 1 575 plants/hm2. (2) The water conservation functions of 0-60 cm soil layer were closely related to soil physical properties

soil permeability and water storage. The variation range of soil bulk density was 1.20~1.43 g/cm3. The total porosity in soil varied from 46.53% to 53.30%. There was a negative correlation between soil bulk density and soil total porosity with afforestation density. The forest land with density of 1 575 plants/hm2 had the smallest soil bulk density and maximum soil total porosity. The permeability of soil mainly depended on the non-capillary porosity of the soil. They had a significant correlation. The permeability of the soil with the density of 1 575 plants/hm2 was the strongest

and the worst with the density of 2 300 plants/hm2. The range of saturated water storage in 0-60 cm soil layer was between 2 792.50 to 3 197.90 m3/hm2. The soil saturated water storage with afforestation density of 1 575 plants/hm2 was the largest. (3) The water conservation functions were evaluated by using the total water storage of forest land. The order of total forest water storage was D1575(3 207.37 m3/hm2) > D2300(3 164.67 m3/hm2) > D1900(3 157.17 m3/hm2) > D1650(3 141.12 m3/hm2) > D1475(3 105.91 m3/hm2) > D1725(2 998.32 m3/hm2) > D1350(2 803.68 m3/hm2). This results matched with the local afforestation specifications of 2 m×3 m. These findings provides a theoretical basis for the sustainable management of Piceacrassifolia plantation in the high and cold region of Loess Plateau of Qinghai Province.