Hydrological Effects of Forest Litter and Soil on Different Density Plantations of Pinus sylvestris L. Var. mongolica Litv. in Mu Us Sandland, Northwest China

摘要

A pilot study of hydrological effects of litter and soil layers was carried out on different densityplantations of Pinus sylvestris L. Var. mongolica Litv. in the southeast of Mu Us Sandland. For thepurpose of evaluating the hydrological function of litter and soil quantitatively, 30 standard plots (10types of forest×3 replications) were investigated. The soil physical characteristics and water-holdingcapacity were determined. The results showed that: (1) The total storage capacity of litter among 10forest types, generally followed by the sequence of forest densities, were P III = P IV > P X > P VII > P IX > P VI> P VII >P V > P II > P I ; the maximum water-holding capacity and effective water-holding capacity of litter,for 10 forest types, were 2.46-8.23 t/hm 2 and 0.163-6.42 t/hm 2 , respectively. (2) There were nosignificant differences in water content, bulk density and the maximum water-holding capacity of soilamongst these forest types, with the variation range of 8.94-16.54%, 1.10-1.66 g/cm 3 and 200.43-266.43 t/hm 2 , respectively. However, the non-pore porosity of soil among these 10 forest types variedgreatly with a variation range of 0.99-4.32%. The hydrological effects of soil were the highest in theP III and P IV plots, and the lowest in the P I plot. (3) The power function model can better indicate highcorrelation coefficients between the water absorption rate of litter and its immersion time, and alsobetween the water-holding capacity of litter and its soaking time. The stable infiltration rates of soil in10 different forest stands were consistent, while they varied greatly with a range of 0.11-0.89 mm/minafter 20 minutes. (4) In this study, the hydrological effects of forest litter and soil in P III and P IV plotswere the best, and the optimal afforestation density was 1500 to 1800 plants per hectare. The resultsshow that thinning should be done timely and appropriately in this study area to prevent the recessionof a forest stand. Besides, it is unapproachable whether Pinus sylvestris Var. mongolica can beplanted in large scale or in high density, and further research is needed.