Abstract: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.