典型黑土区农业流域土壤侵蚀-沉积对土壤养分和酶活性的影响

Effects of Soil Erosion-deposition on Soil Nutrients and Enzyme Activities in An Agricultural Watershed of Chinese Mollisol Region

研究农业流域土壤侵蚀—沉积对土壤养分和酶活性的影响可为土壤侵蚀退化评价提供重要科学依据。选择典型薄层黑土区的宾州河流域为研究区,在流域上游、中游和下游各选取2个代表性坡面,基于137 Cs示踪技术估算土壤侵蚀—沉积速率,分析流域和坡面尺度土壤侵蚀—沉积对土壤养分(有机质、全氮和速效磷)和土壤酶活性(转化酶、脲酶和碱性磷酸酶)的影响。结果表明:(1)土壤侵蚀速率在流域上游最大,分别是流域中游和下游的1.9,11.2倍;坡面尺度上土壤侵蚀速率在坡中部最大,分别是坡上部和坡下部的1.3~2.6,2.8~12.2倍。(2)在流域尺度上,土壤有机质空间分布与土壤侵蚀速率空间分布呈相反的变化趋势,土壤全氮和速效磷含量在流域下游皆大于流域中游;坡面尺度上土壤有机质、速效磷含量、转化酶、脲酶和碱性磷酸酶活性均表现为坡下部>坡中部,说明农地土壤侵蚀降低土壤养分含量和酶活性。(3)流域沉积区土壤沉积速率对土壤有机质、速效磷含量、脲酶和碱性磷酸酶活性有显著影响。(4)土壤有机质和速效磷含量对土壤脲酶和碱性磷酸酶活性有显著影响,表明土壤侵蚀—沉积引起的土壤养分再分布是造成土壤酶活性空间分异的重要原因。

Identifying the effects of soil erosion-deposition on soil nutrients and enzyme activities in agricultural watersheds can provide an important scientific basis for soil erosion evaluation.Binzhou River Basin,a typical thin-layer Mollisol area,was selected as the study area,and two representative slopes were selected in the upstream,midstream and downstream of the basin.137 Cs tracer technique was used to estimate soil erosion-deposition rates and impacts of soil erosion-deposition on soil nutrients(organic matter,total nitrogen and available phosphorus)and soil enzyme activities(invertase,urease and alkaline phosphatase)at both watershed and sloping scales were analyzed.The results showed as follows:(1)The soil erosion rates were the highest in the upstream of the Binzhou River Basin,which were 1.9 and 11.2 times of those in the midstream and downstream,respectively;at the sloping scale,the soil erosion rates were the highest in the middle slope locations,which were 1.3~2.6 and 2.8~12.2 times of those in the upper and lower slope locations,respectively.(2)At the watershed scale,the spatial distribution of soil organic matter and soil erosion rates showed an opposite trend and the contents of total nitrogen and available phosphorus in the downstream were both greater than those in the midstream;on the sloping scale,the contents of soil organic matter and available phosphorus as well as the activities of soil invertase,urease and alkaline phosphatase in the lower slope locations were all greater than those in the middle slope locations,indicating that soil erosion in farmland declined soil nutrient contents and enzyme activities.(3)The soil deposition rates in the deposition areas of the watershed had significant impacts on the contents of soil organic matter and available phosphorus as well as the activities of soil urease and alkaline phosphatase.(4)The contents of soil organic matter and available phosphorus had significant impacts on the activities of urease and alkaline phosphatase,indicating that the redistribution of soil nutrients caused by soil erosion-deposition was an important reason for the spatial differentiation of soil enzyme activities.