We investigated the potential of earthworm casts to emit N₂O, hypothesizing that emission levels are influenced by the species of earthworm and their ecological category. This study examined casts a broad taxonomic and ecological coverage of tropical earthworms, i.e., 16 different species across four ecological categories. We quantified the potential nitrification, N₂O production and consumption as well as the abundance of N-related microbial functional groups, including ammonia-oxidizers, nitrite-reducers, and distinct clades of N₂O-reducers, along with casts chemical properties to determine cast organic matter quality and substrate availability. Earthworm casts exhibited significantly higher concentrations of carbon, nitrogen, and nitrate compared to control soil, while humification index were lower. A negative correlation between humification index and potential N₂O production suggests that more labile substrates in the casts promote higher N₂O flux. Net potential N₂O emissions were higher in the casts of 7 out of 16 species compared to control soil, and all species’ casts showed higher gross potential N₂O production, with substantial interspecific variability. The abundance of nitrite and N₂O reducers was significantly higher in the casts and positively correlated with potential N₂O emissions. Casts from epigeic and mixed categories displayed higher carbon and nitrogen content, abundance of nitrite and N₂O reducers, ammonia-oxidizing bacteria, and potential N₂O production compared to anecic and endogeic categories, which exhibited higher values of humification index. Structural equation modeling indicated that gross potential N₂O production was primarily explained by the abundance of nitrite reducers and substrate availability indicators such as humification index and nitrate concentration. Our study demonstrates significant interspecific variability in N₂O potential emissions from a broad range of tropical earthworm casts, influenced by species feeding behavior, microbial communities, and substrate availability.

我们研究了蚯蚓粪排放 N ₂ O 的潜力，假设排放水平受到蚯蚓种类及其生态类别的影响。这项研究考察了热带蚯蚓的广泛分类学和生态覆盖范围，即涵盖四个生态类别的 16 个不同物种。我们量化了潜在的硝化作用、N ₂ O 的产生和消耗以及与 N 相关的微生物功能群的丰度，包括氨氧化剂、亚硝酸盐还原剂和 N ₂ O 还原剂的不同分支，以及化学性质，以确定铸造有机物质量和基质可用性。与对照土壤相比，蚯蚓粪的碳、氮和硝酸盐浓度明显较高，而腐殖化指数较低。腐殖化指数与潜在的 N2O 产量之间的负相关表明，铸件中更不稳定的基质会促进更高的 N2O 通量。与对照土壤相比，16 个物种中有 7 个的潜在 N2O 排放量较高，而且所有物种的潜在 N2O 总产量均较高，且种间差异较大。铸件中亚硝酸盐和 N2O 还原剂的丰度显着较高，并且与潜在的 N2O 排放量呈正相关。与非内生和内生类别相比，外生和混合类别的铸件表现出更高的碳和氮含量、丰富的亚硝酸盐和 N2O 还原剂、氨氧化细菌和潜在的 N2O 产量，并表现出更高的腐殖化指数值。 结构方程模型表明，潜在的 N2O 总产量主要由亚硝酸盐还原剂的丰度和底物可用性指标（例如腐殖化指数和硝酸盐浓度）来解释。我们的研究表明，多种热带蚯蚓铸件的 N2O 潜在排放量存在显着的种间变异，受物种摄食行为、微生物群落和基质可用性的影响。