陕西榆林樟子松人工林土壤及枯落物水文效应
Hydrological effects of soil and litters in Pinus sylvestris var.mongolica plantations in Yulin,Shaanxi

【目的】研究不同密度樟子松人工林土壤及枯落物的水文效应。【方法】以陕西榆林不同密度（550，800，1 250，1 750，2 050，2 250，3 850株/hm2）樟子松人工林为研究对象，在林下设置标准地采集土壤及枯落物，通过室内试验研究不同密度林地土壤物理性质、土壤持水量及枯落物的持水特性。【结果】7种林分密度樟子松人工林中，密度为800株/hm2林地土壤的含水率最大（6.88%），土壤体积质量最小（1.51 g/cm3），总孔隙度最大（42.99%），土壤有效持水能力最强（147.55 t/hm2）。随着林分密度的增大，林下枯落物总蓄积量不断增加，其值为16.23～27.99 t/hm2，枯落物有效拦蓄量表现为3 850株/hm2＞2 250株/hm2＞2 050株/hm2＞1 750株/hm2＞1 250株/hm2＞800株/hm2＞550株/hm2，其中以林分密度为3 850株/hm2林地的最强，达45.14 t/hm2，是林分密度为800株/hm2林地的1.8倍。不同林分密度下，枯落物持水量与浸泡时间呈对数关系，吸水速率与浸泡时间呈幂函数关系。【结论】在一定范围内，樟子松人工林分密度越大，枯落物总蓄积量越高，持水能力越强；但其土壤含水率、总孔隙度呈先增大后减小趋势，土壤持水能力先增强后减弱。因此，人工林水文功能的充分发挥应综合考虑土壤含水率、孔隙度等土壤物理性质以及林地枯落物蓄积量等持水特性，从而确定最适种植密度。
【Objective】The study aimed to explore the influence of stand density on hydrological effects of soil and litters in Pinus sylvestris var.mongolica plantations.【Method】Taking Pinus sylvestris var.mongolica plantations with different stand densities (550,800,1 250,1 750,2 050,2 250 and 3 850 stem/hm2) in Yulin,Shaanxi as object,standard plots were set for collection of soil and litter samples to investigate soil physical properties,soil water holding capacity,and litter water holding characteristics.【Result】In the seven Pinus sylvestris var.mongolica plantations with different stand densities,the plot with stand density of 800 stem/hm2had the largest soil moisture (6.88%),lowest soil bulk density (1.51 g/cm3),largest total soil porosity (42.99%),and the strongest modified water holding capacity (147.55 t/hm2).Litters reserves increased as the increase of stand density,ranging from 16.23 to 27.99 t/hm2.The modified interception capacity was in the order of 3 850 stem/hm2＞2 250 stem/hm2＞2 050 stem/hm2＞1 750 stem/hm2＞1 250 stem/hm2＞800 stem/hm2＞550 stem/hm2.The highest value (45.14 t/hm2) was 1.8 times of the lowest.Water holding capacity and soaking time had logarithmic relationship,while water absorption rate and soaking time had power function relationship.【Conclusion】Litter volume and water holding capacity increased with the increase of stand density in Pinus sylvestris var.mongolica plantations.However,soil moisture,total soil porosity,and soil water holding capacity firstly increased followed by a decreasing trend.Comprehensive consideration of soil physical properties,such as soil moisture,soil organic matter content,soil porosity and litter water holding characteristics is needed to determine optimal stand densities