退耕还林对贵州喀斯特石漠化区水土保持效果的影响

Effects of Soil and Water Conservation by De-farming and Reafforestation in the Karst Rocky Desertification Regions

为了探明喀斯特石漠化区退耕还林与水土保持效果的关系,采用实地调查与无界径流小区法研究了退耕还林地对贵州喀斯特石漠化区水土保持效果及养分涵养的影响。结果表明:喀斯特石漠化区各类型植被坡地地表径流中的泥沙、养分含量大小顺序均为玉米旱地>退耕还林地>天然灌丛草地>次生阔叶林地;退耕还林后,坡地土壤及养分的流失量明显减少,退耕还林地地表径流中的NH4+、NO3-、PO34-和K+的平均含量分别比玉米旱地减少41.32%、57.08%、30.49%和35.23%,其含量受退耕年限及植被覆盖度的影响较大;退耕还林地土壤中的有效氮、磷、钾含量也明显高于玉米旱地,其平均含量分别比玉米旱地高25.62%、28.21%和63.74%。因此,退耕还林能明显减少土壤侵蚀和养分流失,增加土壤养分含量。

To prove up the relationship between de-farming and reafforestation in the karst rocky desertification regions and the effects of soil and water conservation, the field survey and surface runoff methods were used to study the influence of de-farming and reafforestation on soil and water conservation effect in karst rocky desertification regions in Guizhou and the nutrient conservation. The results showed that the amount of sand and nutrient in the runoff followed a sort order： corn dry land 〉 de-farming and reafforestation land 〉 forest land 〉 shrub-grass land. The amount of soil or nutrient loss reduced obviously, and the average contents of NH4＋ , NO3- , PO4^3- and K＋ in runoff from the land of de-farming and reafforestation decreased by 41. 32%, 57.08%, 30.49% and 35.23%, respectively, compared with corn dry land. These nutrient contents were largely influenced by the years of de-farming and reafforestation and the coverage of plants. Also, the average contents of available N, P, and K in the soils increased by 25.62%, 28.21% and 63. 74% after de-farming and reafforestation. Therefore, de-farming and reafforestation could decrease the soil erosion and the amount of soil nutrient loss to effectively increase soil nutrient level.