Abstract Both organic matter status and earthworm activity may affect the microbial-mediated N2O production in tropical plantations which contribute greatly to the global N2O emission. The representative pantropical earthworm Pontoscolex corethrurus was likely to be increasingly dominant in degraded lands due to intensified disturbances such as understory removal and soil erosion. We noticed that the relatively fertile surface soil plays key roles in fueling both microbes and earthworms. Therefore, we hypothesized that N2O production was stimulated most by earthworm P. corethrurus in less-disturbed tropical plantations where the surface soil layer was conserved. To determine the effect of organic matter sources and P. corethrurus activity on N2O flux in tropical plantation soils, a field mesocosm experiment including four organic treatments with and without earthworms was then conducted. In plant-free mesocosms, mineral soils (60–80 cm layer) received four organic matter treatments: no organic matter (CK), non-fragmented fallen leaves (NL), partially fragmented leaves (PL) and surface soil containing decomposed litter (0–5 cm, SS), which were used to simulate different levels of disturbance-mediated resource depletion. We found that although the population of P. corethrurus declined with the intensity of food resource limitation, mostly P. corethrurus stimulated N2O flux, but occasionally reduced N2O flux in the organic matter-depleted control soils. In contrast, organic matter sources did not exert significant effects on N2O flux. This study indicates that, although the disturbance-induced changes in organic matter supply altered earthworm population size, the presence of P. corethrurus rather than organic matter sources is the determinant of N2O flux in the studied tropical soils. Although the occasionally negative earthworm effects on N2O flux brings uncertainty, the population size-independent positive earthworm effect on N2O flux may simplify the modeling of earthworm contributions to greenhouse gas fluxes.

中文翻译：

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蚯蚓 Pontoscolex corethrurus 而不是有机物质来源的存在间接控制了热带种植园土壤中的 N2O 通量

摘要 有机质状况和蚯蚓活动都可能影响热带人工林微生物介导的 N2O 生产，这对全球 N2O 排放有很大贡献。由于林下移除和土壤侵蚀等干扰加剧，具有代表性的泛热带蚯蚓 Pontoscolex corethrurus 可能在退化土地中越来越占主导地位。我们注意到相对肥沃的表层土壤在为微生物和蚯蚓提供燃料方面起着关键作用。因此，我们假设在较少干扰的热带种植园中，蚯蚓 P. corethrurus 刺激了 N2O 的产生，其中表土层得到了保护。确定有机质来源和 P. corethrurus 活动对热带种植园土壤中 N2O 通量的影响，然后进行了田间中观实验，包括四种有机处理，有和没有蚯蚓。在无植物的中层环境中，矿质土壤（60-80 cm 层）接受了四种有机质处理：无有机质（CK）、非碎片落叶（NL）、部分碎片化叶子（PL）和含有分解凋落物的表层土壤（ 0-5 cm, SS)，用于模拟不同程度的干扰介导的资源消耗。我们发现，虽然 P. corethrurus 的数量随着食物资源限制的强度而下降，但 P. corethrurus 主要刺激 N2O 通量，但偶尔会降低有机质耗尽对照土壤中的 N2O 通量。相比之下，有机物源对 N2O 通量没有显着影响。本研究表明，尽管扰动引起的有机质供应变化改变了蚯蚓种群规模，但 P. corethrurus 的存在而不是有机质来源是所研究热带土壤中 N2O 通量的决定因素。尽管偶尔蚯蚓对 N2O 通量的负面影响带来了不确定性，但与种群大小无关的蚯蚓对 N2O 通量的积极影响可能会简化蚯蚓对温室气体通量贡献的建模。