西藏色季拉山土壤物理性质垂直地带性

以色季拉山为代表的藏东南高原山地的水土流失已成为区域生态环境的重要问题。对色季拉山不同海拔梯度土壤物理性质进行分析,结果表明:(1)除海拔3600、4200m外,土壤容重随土层深度增加而增大;总孔隙度、毛管孔隙度随土层深度增加而减小;非毛管孔隙度随土层变化无明显规律;饱和含水率、毛管含水率、田间持水率均随土层深度增加而减小。(2)不同海拔梯度,土壤容重总均值、总孔隙度、毛管孔隙度和非毛管孔隙度变化范围分别为:0.58—1.10g/cm~3、57.00%—72.47%、53.33%—67.59%和3.20%—4.87%。饱和含水率、毛管含水率、渗透性具有相同规律,均为3800、3400m处最大,3200m和3600m处最小,4000—4600m居中,田间持水率随海拔梯度变化呈M型波动性趋势。(3)土壤物理性质具有较强的空间异质性,各指标间有明显的空间自相关现象。土壤物理性质各指标在不同土层和海拔间有较明显的差异性,人为干扰也是导致土壤物理性质空间异质性的重要原因。(4)总体上,色季拉山表层土壤(0—10cm)物理结构优于深层次(10—30cm)土壤;3200m和3600m处最差,4000—4600m居中,3400—3800m最佳。研究结果提示,以色季拉山为代表的藏东南原始森林地带,土壤结构脆弱,为保持水土,应防止旅游和森林生产经营的过度开发。

Research on vertical zonation of soil physical properties in Sygera Mountain, Tibet

Soil and water loss in the southeastern plateau of Tibet, particularly in Sygera Mountain has become an important problem in regional ecological environment. The soil physical properties of Sygera Mountain at different altitude gradients were analyzed. The results showed that:(1) soil bulk density increased with the increase in soil depth at different elevations, except for 3600m and 4200m. The total porosity and capillary porosity decreased with soil depth at different elevations. The non-capillary porosity was not significantly related to the soil layer. The saturated soil water content, capillary water content, and field capacity decreased with the increase in soil depth at different elevations. (2) The soil bulk density, total porosity, capillary porosity, and non-capillary porosity at different elevations ranged from 0.58-1.10g/cm³, 57.00%-72.47%, 53.33%-67.59%, and 3.20%-4.87%,respectively. The saturated water content, capillary water content, and permeability followed a similar trend, with the maximum values at an elevation of 3800m and 3400m, minimum values at 3200m and 3600m, and intermediate values in the summit area (4000-4600m). Field capacity plotted against altitude revealed an M-shaped trend. (3) The soil physical properties at different elevation had a strong spatial heterogeneity, and the indices revealed spatial auto-correlation with each other. Significant differences in soil physical properties were present among different soil layers and elevations. Moreover, human disturbance was an important reason underlying the spatial heterogeneity of soil physical properties. (4) In general, physical properties of surface soil (0-10 cm) at Sygera Mountain were better than that of deeper soil layers (10-30cm or more). However, physical properties of surface soil at the foot of the mountain (3200m) and 3600m were the worst, whereas those in the summit area (4000-4600m) were intermediate, and those in the hillside areas (3400,3800m) were the best. The present study indicated that soil structure was vulnerable in the virgin forest areas of Sygera Mountain, southeast Tibet. Therefore, tourism, and forest industrial production and management, should be better managed in order to maintain the ability of this forest to conserve water and soil.