基于土壤粒度和大风日数的风蚀风险预报

    Wind erosion prediction based on soil particle size characteristics and strong wind days

    • 摘要: 为寻求一种较为简便、广泛适用的土壤潜在风蚀风险评价方法体系,选取内蒙古中西部的吉兰太戈壁、乌兰布和半固定沙地、毛乌素沙地、武川农田和希拉穆仁草原5种典型风蚀试验区,基于数字图像技术,获取地表不可蚀颗粒含量,结合地区大风日数资料,建立土壤潜在风蚀风险指数方程,并进行实地验证。结果表明:吉兰太戈壁、灌丛地表已经处于粗化过程后期,抗风蚀能力较强,平均抗风蚀指数分别为91.40%和81.40%。由于灌丛群落的存在,乌兰布和沙漠半固定沙地土壤颗粒空间分布差异明显,导致土壤抗风蚀能力呈现不同程度的差异。毛乌素沙地风成沙物质颗粒较细,抗风蚀指数仅为13.40%,极易起沙。应用土壤潜在风蚀风险方程实地表征所得结果与实际情况吻合,与人类活动关系最为密切的农田、草原土壤潜在风蚀风险最高。研究结果可实现科学、有效地预测地表潜在风蚀风险,为干旱、半干旱地区风蚀荒漠化监测提供理论依据和技术支撑。

       

      Abstract: Abstract: Wind erosion is a severe environmental problem in arid, semi-arid region of the world, and it occurs frequently in northwest part of China and leads to soil degradation. Inner Mongolia is located in Northern China as a very important ecological barrier with various of landforms including desert, grassland and forest. In order to quantify the regional soil degradation degree and predict potential wind erosion risk, 5 typical sites of wind erosion, i.e. Jilantai Gebi, Ulan Buh desert, Mu Us sandy land, Wuchuan farmland and Xilamuren Grassland were chosen as experimental sites. Based on digital image technology, the pictures of these 5 sites were taken using Canon EF24-105 mm, and the grey scale information of the images was analyzed by Erdas-Image software; an area compensation equation was established to obtain the actual particle size, and then the residual amount of coarse surface was calculated. On the basis of wind erosion estimation model of Inner Mongolia Houshan Area, surface un-erodible particle (>0.84 mm) was chosen as key indicator combined with local strong wind days, and then an applicable soil erosion potential risk exponential equation was established and the soil potential wind erosion risk was evaluated. The results suggested that wind erosion was a physical process of erodible particle loss, as a result, serious degradation surface kept a high content of coarse grains. Jilantai Gebi and surface around shrub has experienced severe wind erosion, for there existed a large proportion of coarse particles, indicating that the area was in late period of the coarsening process with strong anti-erosion ability, and the average anti-erosion indices were 91.40% and 81.40% respectively. Soil particles of Ulan Buh Desert showed obvious spatial heterogeneous characteristics due to the effect of few shrub communities, and the soil anti-wind erosion ability was Artemisia xerophytica Krasch plot > Artemisia arenaria DC.plot > Nitraria tangutorum plot. In Mu Us Sandy land, aeolian material was the main component and the vegetation coverage was less than 5%; the area was dominated by barchan, and soil particle content showed intensive spatial heterogeneity with variation coefficient of 37%, which was mainly caused by different position of sand dunes. The anti-erosion index was only 13.40% indicating that wind erosion occurred easily in this site. In terms of typical farming land, surface fine material was maintained at a high level due to frequent plow activities, which led to a lower anti-erosion index of 29.40%; on the contrary, due to long-term wind erosion, much fine particle of abandoned farmland got lost, at last soil surface was covered by coarsening grains mostly, and the anti-wind erosion index was greater than that of farming land. Soil particle turned to show obvious spatial heterogeneity in deserted grassland, un-erodible particle decreased along with the distance far away from the tourist area, and the regional average anti-erosion index was 45.20%. Poor soil and strong wind were the main factors contributing to the sand dust in the tested areas. Based on the potential wind erosion risk equation, Jilantai Gebi was in the lowest potential wind erosion risk among the 5 sites, and it showed that soil surface reached a new stable balance. The potential wind erosion risk of shrub communities in Ulan Buh Desert was contrary to anti-wind erosion ability. However, based on the analysis effect, potential wind erosion risk was farmland > abandoned land > shift sand dune, which seemed to be a little bit abnormal. This was because farmland surface was looser than others, and there were different strong wind days among these areas. As a simple prediction equation, it was applicable in different sites of arid areas, especially in small scale predication, as was shown in the results. Farmland and grassland were in higher wind erosion risk and was becoming a new sand source, and human disturbance played an important role in this process.

       

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