以滇池西南部东大河小流域为研究靶区,利用137Cs核素示踪技术,对研究区内林地、草地、耕地3种土地利用类型的土壤侵蚀量及土壤总有机碳(TOC)、总氮(TN)、总磷(TP)流失量进行了定量分析及评价,并通过土壤养分生态化学计量特征(碳氮比C/N、碳磷比C/P、氮磷比N/P)揭示当地土壤肥力状况。结果 表明:(1)不同土地利用方式下土壤侵蚀存在差异。平均侵蚀程度大小表现为耕地[1 538.74 t/(km2·a)]>草地[1 308.82 t/(km2·a)]>林地[81.88 t/(km2·a)],流域整体侵蚀程度介于轻度侵蚀到中度侵蚀之间,但草地、耕地仍高于当地允许流失量。(2)不同土地利用方式对土壤养分含量分布及流失量具有一定影响,并且土壤侵蚀与养分流失关系密切。TOC,TN,TP含量大小表现的规律不尽相同,林地土壤养分流失量最小,土壤养分状况多数在3级以上,土壤肥力状况较好。(3)土壤侵蚀通过影响养分流失对土壤养分化学计量特征产生间接影响,土壤C/N规律为耕地(6.95)>草地(6.14)>林地(3.14); 土壤N/P为林地(10.99)>草地(10.07)>耕地(4.82); 土壤C/P为草地(57.47)>林地(39.94)>耕地(27.55),C/N,C/P,N/P均较低,表明土壤有机质矿化速率较快,并且磷的有效性较高,流域内植被生长在一定程度上主要受N元素影响。
In this study, the soil erosion and nutrients(total organic carbon, total nitrogen and total phosphorus)losses in woodland, grassland and cultivated land were investigated based on 137Cs radionuclide tracer technology at Dongdahe catchment of Dianchi watershed. At the same time, soil fertility conditions in the three land use types were revealed through ecological stoichiometric characteristics of soil nutrients(C/N, C/P, N/P). The results showed that:(1)there were differences in soil erosion under different land use patterns; the average erosion rate decreased in the order: farmland [1 538.74 t/(km2·a)]>grassland [1 308.82 t/(km2·a)]>forestland [81.88 t/(km2·a)]; the average erosion degree of the basin was between mild erosion and moderate erosion, but the erosion rates of grassland and farmland were still higher than the local allowable loss rate;(2)different land use patterns hadcertain effects on the distribution of soil nutrient content and soil nutrient losses; a close relation between soil erosion and nutrient loss was observed; the patterns of TOC, TN and TP contents in three land types were different; the soil nutrient loss in forestland was the lowest, most soil nutrient levels were above grade 3, and the soil fertility was better;(3)soil erosion affected soil nutrient stoichiometric characteristics indirectly by affecting nutrient losses, soil C/N decreased in the order: farmland(6.95)>grassland(6.14)>woodland(3.14); soil N/P decreased in the order: forestland(10.99)>grassland(10.07)>farmland(4.82); Soil C/P decreased in the order: grassland(57.47)>woodland(39.94)>cultivated land(27.55); lower C/N, C/P and N/P indicated that the mineralization rate of soil organic matter was fast and the availability of phosphorus was high. Vegetation growth was mainly affected by N element to a certain extent in this catchment.
