藏北青南高原地表风蚀粗化特征

藏北青南高原长期受风蚀影响,地表粗化现象明显。本研究系统采集该区东西向调查样带内表层（0~1 cm）与浅层（1~10 cm）土壤样品,通过粒度测定、构建能够表征土壤风蚀粗化程度的风蚀粗化指数（WECI）,分析该区地表风蚀粗化特征。结果表明：藏北青南高原土壤中砾石、极粗砂、粗砂等粗颗粒组分在表层土壤中含量较浅层土壤有所增加,自西向东逐渐减少;黏土与粉砂等细颗粒组分相反,表层较浅层土壤中含量明显下降,自西向东逐渐增加。从样带东部的高寒草甸区到中部高寒草原区和西部高寒草原与荒漠草原过渡区,表层土壤环境敏感组分逐渐变粗,各区域平均风蚀粗化指数依次为1.05、1.47和1.77,地表风蚀粗化趋于加剧。现有文献常用的土壤粒度分形维数与土壤质地粗化度是刻画土壤质地粗细程度的静态指标,无法衡量风蚀导致的地表颗粒组成变化,本文构建的风蚀粗化指数克服了上述不足,且具有风蚀动力学依据。

Characteristics of land surface coarsening by wind erosion on the Northern Tibet and Southern Qinghai Plateau

Under the long-term influence of wind erosion, land surface coarsening on the Northern Tibet and Southern Qinghai Plateau is obvious. In this paper, the surface soil (0-1 cm deep) and shallow soil (1-10 cm deep) were systematically sampled in an east-west directional survey transect. By grain-size composition measurement and constructing a wind erosion coarsening index (WECI) that can depict the soil wind erosion coarsening degree, wind erosion coarsening characteristics of the land surface on the plateau were analyzed. Results show that the contents of coarse particles such as gravel, very coarse sand, and coarse sand in surface soil are higher than those in shallow soil, and the contents of coarse particles decrease gradually from west to east. On the contrary, compared with shallow soil, the contents of fine particles such as clay and silt decrease significantly in surface soil and increase gradually from west to east. From the eastern alpine meadow region (average WECI = 1.05) to the central alpine steppe region (average WECI = 1.47) and the western transition region between the alpine steppe and desert steppe (average WECI = 1.77), the degree of land surface coarsening caused by wind erosion aggravates. The fractal dimension and soil texture coarsening indexes commonly used in existing research are static indicators that can describe the soil texture status but cannot measure the change in surface soil particle composition caused by wind erosion. The wind erosion coarsening index constructed in this paper overcomes the above shortcomings and has the basis of wind erosion dynamics.