龙门山地震带坡耕地土壤侵蚀对有机碳迁移的影响

发布时间：2018-12-20 16:49

【摘要】：坡耕地土壤再分布对土壤有机碳(SOC,soil organic carbon)迁移的作用机制研究已成为土壤侵蚀学研究的热点,然而目前极少有研究关注地震后生态脆弱的龙门山地震带坡耕地土壤侵蚀机理及其导致的土壤有机碳再分布规律。该研究选择龙门山地震带内(都江堰市)一块陡坡耕地和一个梯田系列,采用137Cs法和野外调查,对比分析强震导致田埂垮塌和未受损情况下坡耕地土壤侵蚀空间变化特征和有机碳运移变化机理。结果表明,该区黄棕壤有效137Cs背景值为1 473 Bq/m2;坡度较小的坡式梯田内部上坡表现为侵蚀,下坡表现为沉积,同时,上部梯田的侵蚀速率高于下部梯田,但整个梯田系列净侵蚀量非常小,这表明梯田之间由于缺乏田埂的保护,水力也起着侵蚀、搬运上坡梯田土壤的作用,但是整个坡式梯田系列可以起到较好的保土作用,同时,坡式梯田内部主要以耕作侵蚀为主,是造成梯田上部坡位土壤流失严重的主要原因;陡坡耕地的地形为复合坡,由于田埂垮塌导致其土壤侵蚀速率显著高于坡式梯田系列,在整个坡面上,除了坡顶土壤侵蚀速率高之外,下坡坡度变大(曲率较大)的部位土壤侵蚀速率也非常高,同时,土壤沉积也发生在2个坡位(中下坡坡度较缓的部位和坡脚部位);在梯田系列和陡坡耕地上,SOC与土壤137Cs的空间变化规律较为一致。研究结果表明,在龙门山地震带,质量较好的石埂梯田仍然发挥着较好的土壤保持效果,同时,耕作侵蚀是该区坡耕地上一种重要的土壤侵蚀形式,在制定相应的土壤保持措施时,必须充分考虑耕作侵蚀的作用,才能有效地控制土壤侵蚀,此外,该研究结果还表明采用137Cs核素示踪技术可以比较科学地解释该区域的土壤侵蚀速率和SOC的空间变异规律。
[Abstract]:The mechanism of soil redistribution on soil organic carbon (SOC,soil organic carbon) migration in sloping farmland has become a hotspot in soil erosion. However, little attention has been paid to the mechanism of soil erosion and the redistribution of soil organic carbon (SOC) in sloping farmland in Longmen Mountain seismic zone. In this study, a steep slope cultivated land and a terraced field in the Longmen Mountain seismic belt (Dujiangyan City) were selected, and 137Cs method and field investigation were used. The spatial variation characteristics of soil erosion and the mechanism of organic carbon transport in sloping farmland caused by strong earthquakes were analyzed. The results showed that the background value of available 137Cs of yellow brown soil was 1 473 Bq/m2;. At the same time, the erosion rate of the upper terrace is higher than that of the lower terrace, but the net erosion amount of the whole terrace series is very small. This indicates that due to the lack of field ridge protection between terraces, water power also plays an erosion role in transporting the upper slope terrace soil, but the whole slope terrace series can play a better role in soil conservation, at the same time, In slope terrace, tillage erosion is the main reason, which is the main cause of soil loss in the upper slope of terrace. The topography of steep slope cultivated land is compound slope. The soil erosion rate is significantly higher than that of slope terrace series due to the collapse of field ridge. In the whole slope, except for the high soil erosion rate at the top of slope, the soil erosion rate of steep slope is higher than that of terrace. The soil erosion rate is also very high in the lower slope where the slope becomes larger (curvature is larger), and the soil deposition also occurs in two slope positions (the middle slope is slower and the slope foot is at the bottom). In terrace and steep slope farmland, the spatial variation of SOC and soil 137Cs is consistent. The results show that in the Longmen Mountain seismic belt, the terraces with good quality still play a better role in soil conservation, and tillage erosion is an important form of soil erosion on sloping farmland in this area. In formulating appropriate soil conservation measures, the role of tillage erosion must be fully taken into account in order to effectively control soil erosion, The results also show that the 137Cs tracer technique can scientifically explain the soil erosion rate and the spatial variation of SOC in the region.
【作者单位】：绵阳师范学院生态安全与保护四川省重点实验室;中国科学院水利部成都山地灾害与环境研究所中国科学院山地灾害与地表过程重点实验室;
【基金】：生态安全与保护四川省重点实验室开放基金资助(ESP201303) 国家自然科学基金(41401313) 四川省应用基础研究计划项目(2014JY0067)
【分类号】：S157.1

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