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从防止水土流失和土壤水分容量两个方面出发,分析了以森林植被为主体的植物系统的覆盖率、植被盖度与形成良好的健康的森林水分生态环境和水土保持功能的关系。分析了小流域森林覆盖率与水蚀的关系,地块尺度上植被盖度与水蚀的关系。提出根据最大土壤侵蚀量、年允许土壤流失量和小流域的水分供应关系来确定区域宜林地林分面积与适宜森林覆盖率。根据水分、树种、林龄和立地条件对森林密度做具体分析。研究表明:在黄土区小流域尺度,合理的森林分布是防治水蚀的关键;适宜植被盖度是保证水土保持功能持续的关键,乔木成林林分郁闭度达到40%,草本植物的盖度达到90%就具有较好的防蚀功能,植被盖度与生物量同时处于适宜状态时,林分的水土保持功能最佳。研究认为水土保持有效植被盖度不应低于有效盖度(群落下土壤流失量等于允许流失量),最大为临界盖度(群落下土壤流失量为自然侵蚀量),群落灌层下死被物应具有一定厚度为1.0～2.0cm。研究表明在山西省吉县,阳坡刺槐造林密度小于2250株/hm2,以1111株/hm2为最佳;成林密度为300～1800株/hm2,以小于1500株/hm2为佳。
From the perspectives of preventing soil erosion and soil water content, the paper analyzes the coverage of plant systems mainly based on forest vegetation, and the relationship between vegetation coverage and the formation of a healthy and healthy forest water environment and soil and water conservation functions. The relationship between forest coverage and water erosion in small watershed was analyzed. The relationship between vegetation cover and water erosion at the plot scale was analyzed. According to the relationship between the maximum soil erosion and annual allowable soil loss and the water supply in small watershed, the paper proposes that the area of suitable forest stands and suitable forest coverage should be determined. According to the water, tree species, forest age and site conditions to do a detailed analysis of forest density. The results show that the reasonable forest distribution is the key point to prevent water erosion in the small watershed scale of loess area. The suitable vegetation coverage is the key to ensure the sustainable function of soil and water conservation. The coverage of arbor forest reaches 40%, the coverage of herbaceous plants When it reaches 90%, it has better anti-corrosion function. When the vegetation cover and biomass are in proper condition, the function of water and soil conservation is the best. It is concluded that the effective vegetation coverage of soil and water conservation should not be less than the effective coverage (the soil loss under the community is equal to the allowable loss), the maximum is the critical coverage (the soil erosion under the community is the natural erosion) Material should have a certain thickness of 1.0 ~ 2.0cm. The results showed that the afforestation density of Robinia pseudoacacia was less than 2250 plants / hm2 in Ji County of Shanxi Province, with 1111 plants / hm2 being the best. The density of forest plantations was 300-1800 plants / hm2, but less than 1500 plants / hm2.