东北黑土坡面降雨和汇流对土壤团聚体流失和颗粒迁移的影响

Impacts of slope rainfall and inflow in Mollisol region of Northeast China on the soil aggregate loss and particle transport

分析降雨和汇流对坡面土壤团聚体流失和颗粒迁移的影响,可加深对土壤侵蚀退化过程的认识,也为土壤资源可持续利用提供科学依据。采用室内模拟降雨和汇流试验,通过设计2个降雨强度(50和100 mm/h,即R_(50)和R_(100))、1个汇流强度(100 mm/h,即I_(100))以及降雨与汇流组合(50 mm/h降雨强度+50 mm/h汇流强度(R_(50)I_(50))、50 mm/h降雨强度+100 mm/h汇流强度(R_(50)I_(100))、100 mm/h降雨强度+50 mm/h汇流强度(R_(100)I_(50)))试验,分析降雨和汇流对黑土坡面土壤团聚体流失和颗粒迁移的影响。结果表明:1)在试验供水量相同时,R_(100)试验处理的坡面土壤侵蚀速率分别是R_(50)I_(50)的1.9倍和I_(100)的2.4倍,试验处理R_(100)I_(50)的土壤侵蚀速率是R_(50)I_(100)的1.3倍,表明降雨对坡面水蚀的作用大于汇流;2)在降雨主导的坡面水蚀过程中,R_(50)、R_(100)、R_(50)I_(50)和R_(100)I_(50)试验处理下的<0.25 mm微团聚体流失量比例较试验土壤分别增加20.6%、16.7%、17.9%和21.8%,而在汇流主导的坡面水蚀过程中,I_(100)和R_(50)I_(100)试验处理下的≥0.25 mm团聚体流失量比例分别为61.9%和65.2%,表明坡面汇流对黑土团聚体的分散作用小于降雨;且平均质量直径能更好地反映土壤团聚体流失特征;3)R_(100)、I_(100)和R_(50)I_(50)试验处理下砂粒和黏粒流失量比例较R_(50)增加1.4%~9.5%,R_(50)I_(100)和R_(100)I_(50)试验处理下砂粒流失量比例较R_(100)、I_(100)和R_(50)I_(50)试验处理增加0.8%~4.0%,其较R_(50)增加3.7%~6.0%,但粉粒和黏粒比例相应减少,表明粗颗粒流失随坡面汇流量的增加而增加。总之,降雨对黑土团聚体的破碎作用大于坡面汇流作用,坡面水蚀过程中泥沙颗粒的分选取决于降雨和汇流对坡面水蚀的作用程度。

[Background]Soil loss area on the slope croplands of the Chines Mollisol reached 214100 km 2,accounting for 19.7%of the totle land area.Soil aggregates loss and particle transport is often identified as the main mechanism that leads to nutrient loss.This reduces soil fertility and affects the utilization of Mollisol resources.Thus,to study the effects of rainfall and inflow on soil aggregate loss and particle transport may deepen the understandings of soil degradation processes driven by soil erosion and provide scientific basic for soil resource sustainability.[Methods]This study applied simulated rainfall and inflow experiments to investigate effects of rainfall and inflow on soil aggregate loss and particle transport in a 10°sloping landscape of Mollisol region of Northeast China.The experimental treatment included two rainfall intensities of 50 and 100 mm/h(R_(50)and R_(100)),one inflow rate of 100 mm/h(I_(100)),and the combinations of rainfall intensity and inflow rate(50 mm/h rainfall intensity+50 mm/h inflow rate(R_(50)I_(50)),50 mm/h rainfall intensity+100 mm/h inflow rate(R_(50)I_(100)),100 mm/h rainfall intensity+50 mm/h inflow rate(R_(100)I_(50))).[Results]1)Under the same amount of water supply,the sloping soil erosion rate under the R_(100)treatment was 1.9 and 2.4 times compared with the R_(50)I_(50)and I_(100)treatments,respectively;and the soil erosion rate under the R_(100)I_(50)treatment was 1.3 times compared with R_(50)I_(100)treatment,which indicated that the effect of rainfall on sloping soil erosion was greater than that of inflow.2)When rainfall played a dominant role in the process of sloping water erosion,such as the R_(50),R_(100),R_(50)I_(50)and R_(100)I_(50)treatments,the loss of<0.25 mm aggregates increased by 20.6%,16.7%,17.9%and 21.8%respectively,compared with the tested soil.When inflow took a dominant role in the process of sloping water erosion,such as the I_(100)and R_(50)I_(100)treatments,the loss of≥0.25 mm accounted for 61.9%and 65.2%,respectively,which demonstrated that the dispersion effect of inflow water on Mollisol aggregates was less than that of rainfall.Moreover,MWD(mean weigh diameter)value could better reflect the characteristics of soil aggregate loss.3)The total loss of sand and clay particles under the R_(100),I_(100)and R_(50)I_(50)treatments increased by 1.4%-9.5%,compared with the R_(50)treatment;the proportion of sand particle loss under the R_(50)I_(100)and R_(100)I_(50)treatments increased by 0.8%-4.0%,compared with the R_(100),I_(100)and R_(50)I_(50)treatments;and it increased by 3.7%-6.0%compared with the R_(50)treatment;while the total proportion of silt and clay particles decreased accordingly,indicating that the loss of coarse particles increased with an increase of inflow rates.[Conclusions]The dispersion action of rainfall on Mollisol aggregates was larger than that of inflow and the sorting action of sediment particles in the depended on the action degree of rainfall and inflow in sloping water erosion process.