耕作扰动对喀斯特土壤可溶性有机质及其组分迁移淋失的影响

土壤可溶性有机质(DOM)及其组分淋失特征研究对深入理解干扰作用下土壤碳氮养分损失机制具有重要意义,本研究基于翻耕模拟试验,分析喀斯特石灰土可溶性有机碳(DOC)、可溶性有机氮(DON)、及DOM官能团组分的淋失动态特征及其对不同耕作频率的响应,并探讨其影响因子。结果表明:(1)土壤DOC与DON的淋失量均随翻耕频率的增加而增加,但4个官能团特征参数对翻耕频率响应均不显著;DOC/DON淋失比随翻耕频率的增大而减少,DON占淋溶水可溶性总氮(TDN)比例随翻耕频率增加而增加。(2)DOC和DON月淋失量同时受翻耕处理与季节变化及其交互作用的影响,4个官能团特征参数仅受季节变化的影响;翻耕处理实施后,DOC月淋失量表现为初期大、后期小,各处理间差异性逐渐降低;但DON月淋失量初期小、后期大,各处理间差异性逐渐增大。(3)DOC淋失量与4个官能团特征参数呈显著负相关(P0.05),与Ca~(2+)、NH_4~+-N的淋失量呈显著正相关;DON淋失量与4个官能团参数无显著相关关系,与Mg~(2+)淋失量呈显著正相关关系。以上结果表明耕作扰动会加剧土壤DOM淋失,但淋失组分中稳定性组分没有变化,意味着耕作干扰将导致土壤有机质的持续损失,且由于其淋失组分碳氮比(DOC/DON)随扰动频率增加而降低,DON/TDN比随扰动频率增加而增加,持续的耕作干扰将大大增加水体氮素污染风险。

The impacts of tillage on soil soluble organic matter and its movement and leaching in karst area

The study of soil soluble organic matter (DOM) and its component leaching characteristics is of great significance in understanding the mechanism of soil carbon and nitrogen nutrient loss under disturbance. Based on the tillage simulation trial, we analyzed the leaching dynamic characteristics of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and the functional components changes of the DOM in karst calcareous soil and their responses to different tillage frequencies. The main impact of these dynamics was also explored in this study. Our results showed that the leaching amount of DOC and DON increased as the tillage frequency increased, but it did not happen in the four functional group parameters. As the tillage frequency increased, the ratio of DON to total dissolved nitrogen (TDN) increased, but the DOC/DON ratio decreased. The monthly leaching amount of DOC and DON was impacted by tillage treatment, seasonal variation and their interactions. However, the four functional group parameters were only impacted by the seasonal variation. During the experiments, the monthly leaching amount of DOC decreased gradually and the differences among treatments were also reduced, but the leaching amount of DON increased gradually and the differences among treatments increased. The leaching amount of DOC showed a negative relationship with the four functional group parameters, but a positive relationship with the leaching amount of Ca²⁺ and NH₄⁺-N (P < 0.05). The leaching amount of DON had a positive relationship with the leaching amount of Mg²⁺ (P < 0.05), but no significant relationship with the four functional group parameters. We concluded that the tillage increased the leaching amount of DOM, but did not influence the leaching of its stable components, indicating a continuing losses of soil organic matter and a high risk of nitrogen pollution in water would happen if the tillage frequency increase.