东北松嫩典型黑土区长缓坡耕地土壤侵蚀沿坡长变化规律及其对土壤质量的影响

东北黑土区,尤其是农垦地区,是我国重要的粮食生产基地。土壤侵蚀导致耕地质量严重退化,威胁粮食安全。选取克山农场坡长为1020 m的直型坡、凹型坡和凹—直复合型坡耕地,利用¹³⁷Cs示踪技术估算坡面土壤侵蚀模数,测定土壤有机碳作为耕地土壤质量参数,揭示典型黑土区长缓坡耕地土壤侵蚀强度沿坡长变化规律及耕地土壤质量参数的响应。结果表明：（1）不同坡形长缓坡耕地土壤侵蚀差异显著,直型坡多年平均侵蚀速率（3040 t·km^-2·a^-1）<复合型坡（3395 t·km^-2·a^-1）<凹型坡（4220 t·km^-2·a^-1）。（2）直型坡、凹型坡、凹—直复合型坡均呈现出侵蚀强—弱周期性变化规律,其振荡周期分别为380 m、250 m和300 m。（3）土壤有机碳含量与土壤侵蚀速率呈极显著负相关关系,其沿坡长变化规律与土壤侵蚀速率沿坡长变化规律相反。土壤侵蚀是造成黑土坡耕地土壤质量退化的直接原因,研究结果可为黑土长缓坡耕地水土保持措施的精准布设及土壤养分管理提供理论支持。

Variation of soil erosion intensity along the long gentle farming slopes and its influence on soil quality in the typical mollisol region,Songnen Plain,Northeast China

The mollisol region is one of the main grain-producing bases in China, especially the long gentle slopes. Unfortunately, more than 80% of farmland there was suffering from soil erosion, but the variation of soil erosion along the long gentle slopes was still unclear, which will make it more difficult to control soil erosion and protect soil resources. Therefore, the aim of this study was to find the variation law of soil erosion along the gentle slopes. Three gentle slopes (a straight slope, a concave slope and a compound slope ) in Keshan Farm No. 5 were selected as the objects. Soil samples were collected at 30 m intervals along the slopes in early May, 2019. Then the ¹³⁷Cs-activity was measured to evaluate the soil erosion and deposition rates, and to measure soil organic carbon as a parameter of cultivated land soil quality. Wavelet analysis was employed to quantify the variation of soil erosion along the gentle slopes and the response of cultivated land soil quality parameters. The results showed that: (1) The annual average erosion rates of straight slope, composite slope and concave slope are 3040 t·km^-2·a^-1, 3395 t·km^-2·a^-1 and 4220 t·km^-2·a^-1, respecctively. (2) The main changing periods of the whole straight gentle slope, the concave gentle slope, and the compound gentle slope were 380 m, 250 m, and 300 m, respectively. (3) There was a significant negative correlation between soil SOC content and soil erosion rate, and the spatial distribution of soil SOC along the slope length was opposite to that of soil erosion rate, indicating that soil erosion is a key driving factor for soil degradation. Conclusions of this study can help to formulate the targeted soil and water conservation measures for the realization of soil nutrient management along long gentle slope and provides theoretical guidance for soil erosion control of the long gentle cultivated slopes in the mollisol region of Northeast China.