西藏冷杉原始森林土壤物理性质特征分析

CHARACTERISTIC ANALYSIS OF SOIL PHYSICAL PROPERTIES OF ABIES GEORGEI VAR.SMITHII VIRGIN FOREST IN TIBET

在西藏东南部色季拉山森林生态系统定位研究站 ,采用定位和典型样地研究法 ,对该区森林的主要森林类型急尖长苞冷杉 (Abiesgeorgeivar .smithii)原始林林内和林外 (采伐迹地 )土壤物理性质进行了为期两年的观测和对比分析。结果表明 :林内A层土壤容重小于林外A层土壤容重 ,分别为 0 74和 0 92 ,B、C两层 ,林内和林外分别为 0 94、1 34和 0 99、1 2 2。饱和持水量、毛管持水量、田间持水量、非毛管孔隙度、毛管孔隙度和总孔隙度相比较 ,林内A层均大于林外A层 ,B层则相差不明显。随土层深度增加土壤含水量呈下降趋势 ,表层 (0～ 10cm)含水量最高 ,林内、林外分别为 75 %和 6 3% ,5 0cm以下土壤含水量趋于稳定 ,为 30 %～4 5 % ,并依此区分出土壤水分弱利用层、利用层和调节层 3个层次。土壤含水量年变化有明显的规律 ,在冬季1、2月达到最高 ,而在生长季土壤含水量变化幅度不大 ,并依此界定出土壤水分消耗期、积累期、消退期、稳定期 4个时期。林内A层、B层的渗透性能均好于林外A层、B层 ,达到稳渗速度所需时间林内A层比林外A层要少 ,分别为 10min和 4 5min ,B层所需时间要长 ,分别为 70min和 4 5min。总体表明 ,林内土壤物理性状优于林外 ,说明森林受到干扰破坏后土壤物理性质发生了明显变化 ,土壤物?

Abies georgei var. smithii virgin forest was main distribution type in southeastern area of Tibet. By adopting the posting and typical-plot method, the physical properties of the soils inside and outside the forest was studied, through two year observation (1999～2000) in Sejila Mountain Research Station of Forest Ecosystem. The bulk densities of layer A, layer B, and layer C soils was 0 74, 0 94, and 1 34 respectively inside forest and was 0 92, 0 99, and 1 22 respectively outside forest, which indicated that the bulk density for layer A inside forest was less than that of outside forest, while for B and C layers there existed no significant difference between inside and outside forest. By comparison of the saturated moisture capacity, capillary moisture capacity, field moisture capacity, non capillary porosity, capillary porosity, and the total porosity of soil, all values of these factors for layer A soil inside forest were higher than that of outside forest, but those for layer B had no marked difference between inside and outside forest. With depth increasing, the soil water content decreased. It was the highest in surface layer (0～10?cm), with a maximum value of 75% inside forest and 63% outside forest, and tended to be stable below 50 cm (30%～40%). Based on change law of soil water and water absorption and utilization of plant root, the soil water utilization of Abies georgei var. smithii forest was first divided into three levels: weak utilization layer (0～10?cm), utilization layer (10～50?cm), and regulating layer (below 50 cm). The soil water content of the forest was the highest in January and February in winter and had little change in growing season. The dynamic of soil water content was divided into consumptive, accumulative, receded, and stable periods. The permeability of both layer A and layer B soils in forest were better than those of outside forest. The time for reaching the stable permeation in layer A was 10 min and 45 min respectively for inside and outside forest.The results showed that the soil physical properties inside forest were superior to that of outside forest. It also indicated that the soil physical properties would be changed obviously and evolved towards adverse directions after forest interfered or destroyed.