【摘要】 很少有关于直接测定强度耕作侵蚀引起土壤退化过程的报道。我们的目的是确定应用137Cs和210Pbex直接定量评价耕作侵蚀对土壤有机质(SOM)坡面运移影响的可能性。我们在黄土高原陡坡耕地上进行了50次犁耕活动,并将与其相临的另一块陡坡耕地作为对照。在对照坡地不同坡位,137Cs浓度均匀分布于上部0～30cm土层,而210Pbex浓度在坡上部和坡中部随土层深度增加呈现线性递减,在坡下部呈指数函数递减。0～30cm土层中土壤有机质含量显著大于30cm深度以下土层,并在坡中部和坡下部呈现与210Pbex类似的土壤剖面分布特征。与对照坡地比较,50次犁耕活动导致坡上部、坡中部0～45cm土层的SOM含量分别降低了38%和47%,坡下部0～100cm土层中的SOM含量却提高了18%。坡上部土壤剖面中137Cs浓度的加权平均值从1.48Bq/kg降低到0.29Bq/kg,坡中部从2.53Bq/kg减少到0.33Bq/kg,坡下部从1.48Bq/kg提高到2.81Bq/kg。210Pbex浓度的剖面加权平均值在坡上部从27.71Bq/kg下降到6.15Bq/kg,在坡中部和坡下部分别从35.46Bq/kg和25.53Bq/kg降低到1.57Bq/kg和19.40Bq/kg。137Cs和210Pbex的剖面分布与SOM在p<0.001水平呈显著相关,相关系数R2值在对照坡地为0.81～0.86,在犁耕实验坡地为0.86～0.91。实验结果表明,环境放射性核素137Cs和210Pbex在黄更多还原

【Abstract】 Few direct measurements have conducted to investigate the dynamic process of soil degradation as affected by intensive tillage at the field level. Our objective is to test the potential of 137Cs and 210Pbexfor directly assessing the movement of SOM on the slope land as affected by tillage operations. We conducted 50 plowing operations over a 5day period using a donkeydrawn moldbordplow on steep backslope of the Chinese Loess Plateau. Profile variations of 137Cs, 210Pbex and SOM contents were measured at upper, mid, and lower portion of the slope after 50 plowing operations. Intensive tillage effects on 137Cs, 210Pbex and SOM contents were determined from a control slope adjacent to experimental slope. 137Cs concentration was uniformly mixed in the upper 0~30 cm of soil whereas 210Pbex showed a linear decrease at upper and mid portion, and an exponential decrease with depth on the lower portion of the control slope. SOM contents of 0~30 cm layers were much higher than the soil layers below 30 cm on the control slope, and showed a similar decrease pattern to profile pattern of 210Pbex on the mid and lower portion of the control slope. Fifty 50plowing operations resulted in a decrease of SOM content (g/kg) by 38% and by 47% for the soil layers of 0~45 cm at upper portion and mid portion, respectively. However, the lower position showed an increase of SOM content by 18% in the soil layers of 0~100 cm after 50 plowing operations. Weighed mean values of 137Cs concentrations decreased from 1.48 Bq/kg to 0.29 Bq/kg at upper position, from 2.53 Bq/kg to 0.33 Bq/kg at mid position, and increased from 1.48 Bq/kg to 2.81 Bq/kg at lower position. Weighed mean values of 210Pbex concentrations decreased from 27.71 Bq/kg to 6.15 Bq/kg at upper position, from 35.46 Bq/kg to 1.57 Bq/kg at mid position, and from 25.53 Bq/kg to 19.40 Bq/kg at lower position. Profile concentrations of 137Cs and 210Pbex are significantly correlated with SOM contents with R2 values of 0.81~0.86 for control slope, and 0.86~0.91 for experimental slope. Our results suggested that fallout 137Cs and 210Pbex could be used directly for quantifying soil qualitysoil redistribution relationship as affected by tillage erosion. 更多还原