中文摘要：

为更好地理解侵蚀土壤质量变化,该文利用137Cs技术探讨了川中丘陵区紫色土陡坡耕地土壤侵蚀对土壤生物学肥力的影响。结果表明,与无侵蚀的坡地相比,陡坡耕地土壤微生物量碳含量及碱性磷酸酶、蔗糖酶活性分别显著降低41%、44%、17%,土壤生物学肥力退化指数MFDI达-35%。陡坡耕地土壤蔗糖酶活性与137Cs浓度显著正相关（r=0.643,p=0.024）,表明蔗糖酶活性随土壤侵蚀强度增大而降低。耕作侵蚀造成的陡坡耕地上坡土壤损失导致土壤微生物量碳含量、碱性磷酸酶、脲酶及蔗糖酶活性最低,而耕作侵蚀造成的陡坡耕地坡底土壤堆积导致这4个微生物特性最高,结果陡坡耕地这些微生物特性的空间变异分别增大2.8、0.8、1.4、4.5倍。紫色土陡坡耕地土壤生物学肥力退化与空间变异性增大在今后的土地管理中应引起关注。

英文摘要：

In order to better understand erosion-induced changes in soil quality,soil erosion impacts on soil microbial fertility of a purple soil with steep sloping farmland were explored in the Sichuan Basin of China by using 137Cs technique.Results showed that the contents of soil microbial carbon（MBC） and activities of soil alkaline phosphate and invertase significantly decreased by 41%,44% and 17%,respectively,in these farmlands compared to a control slope,resulting in an obvious deterioration in soil microbial fertility with a 35% decrease in MFDI（soil microbial fertility degradation index）.A significantly positive correlation was found between soil invertase activity and 137Cs inventory（r=0.643,p=0.024）,suggesting soil invertase activity decreases with increasing soil erosion.Soil erosion by tillage resulted in the lowest soil MBC contents and enzyme activities in upslope positions,whereas soil accumulation by tillage created the highest soil MBC contents and enzyme activities in bottom positions.As a result of soil redistribution,the variations in soil MBC,alkaline phosphate,urease and invertase increased by 2.8,0.8,1.4 and 4.5 times,respectively,in these farmlands than those in the control slope.Land management strategies should involve combating the deterioration and increased spatial variation in soil microbial fertility in purple soil with steep sloping farmland.