青海省大通县退耕还林对土壤理化性质的影响

Effect of Returning Farmland into Forest on Soil Physicochemical Properties in Datong County of Qinghai Province

为全面了解退耕还林对土壤理化性质的影响,在青海省大通县选取退耕年限分别为5 a以内、5～10 a、10～20 a、20 a以上的青海云杉群落及其对比的青海云杉天然次生林及耕地群落,采用标准地调查法,分层取土样,对各群落表层和中下层土壤理化性状进行对比分析,结果表明：土壤容重、总孔隙度、毛管孔隙度、土壤团粒、大团聚体含量均表现为天然林地〉退耕地〉耕地,且随着退耕时间的延长,土壤孔隙状况和结构性能越来越接近于天然林地;土壤有机质、全氮、速效钾、CEC均表现为天然林地〉退耕地〉农耕地,而且与农耕地相比,退耕地土壤碱性有了明显的改善,且随着退耕时间的延长,越来越偏向于天然林地。

In order to know the effect of returning farmland into forest on soil physicochemical properties, the various plant communities of Picea crassifolia with different converting time（5 years below, 5 - 10 years,10-20 years and 20 years above）together with the contrastive types of natural forest and cultivated farmland have been selected in Datong county of Qinghai. And the soil physicochemical properties in the top, middle and bottom layer of these different communities were comparatively analyzed. The main result shows that returning farmland into forest has a great impact on soil physicochemical properties. Soil bulk density, total porosity, capillary porosity, soil aggregate, large aggregate have shown for the natural woodland〉converted farmland〉farmland, and as the extension of the time, the performance of returning farmland to forest is getting closer and closer to natural forest land. Meanwhile the content of soil organic matter, total N, rapid available K, CEC have shown the same for the natural woodland〉converted farmland〉 farmland. Compared with farmland, the pH value of soil is a marked improvement, as the extension of the time, the performance of returning farmland to forest is getting closer and closer to natural forest land.