Earthworm-microbial interactions controlling nitrous oxide production in perennial grass- and legume- based agroecosystems using stable isotopes and molecular markers

蚯蚓对土壤肥力和作物产量的贡献是众所周知的。具有多年生植被的农业生态系统，如以草和豆科植物为基础的干草地，支持大量的蚯蚓种群，因为土壤未受到耕作的干扰，而衰老的植物残留物是蚯蚓的食物来源。在这些条件下，蚯蚓创造的结构，如地表和地下粪便（粪便颗粒），丘墩（土壤表面的土壤-凋落物混合物）和洞穴是无数的。这些结构是微生物硝化菌和反硝化菌的有利栖息地，它们产生一氧化二氮，一种强效的温室气体，作为它们代谢的副产品。我的研究小组以前的实验室研究表明，蚯蚓刺激一氧化二氮的产生，这使我假设蚯蚓-微生物的相互作用导致一氧化二氮在小尺度（微观世界，小块田地）的产生，并可能在农业生态系统水平上促进季节性一氧化二氮的排放。这些生物相互作用将通过尖端的研究工具进行评估，包括15N同位素稀释和DNA方法（amoA， nosZ和其他相关基因的q-PCR扩增，DNA稳定同位素探测）。这些先进的技术极大地增加了我们发现新生物的机会，并获得了微生物介导的N转化的新见解。描述导致土壤一氧化二氮排放的蚯蚓-微生物关系的数学函数将被纳入预测生态系统水平模型（DNDC, ecosys），这些模型最终可能被用于根据IPCC第三阶段方法计算国家温室气体清单。在未来五年内，该项目将培养12名具有专业知识和分析技能的高素质人才，这些人才是环境科学研究岗位所急需的。

Earthworms are well known for their contribution to soil fertility and crop production. Agroecosystems with perennial vegetation, such as grass- and legume-based hayfields, support large earthworm populations because soils are undisturbed by cultivation and senescing plant residues are a food source for earthworms. Under these conditions, earthworm-created structures like surface and subsurface casts (fecal pellets), middens (soil-litter mixture at the soil surface) and burrows are numerous. These structures are a favorable habitat for microbial nitrifiers and denitrifiers that produce nitrous oxide, a potent greenhouse gas, as a byproduct of their metabolism. Previous laboratory studies by my research group have shown that earthworms stimulate nitrous oxide production, leading me to hypothesize that earthworm-microbial interactions lead to nitrous oxide production at small scales (microcosms, small field plots) and may contribute to seasonal nitrous oxide emissions at the agroecosystem level. These biological interactions will be evaluated with cutting-edge research tools, including 15N isotope dilution and DNA methods (q-PCR amplification of amoA, nosZ and other relevant genes, DNA-stable isotope probing). These advanced techniques tremendously increase our chance of discovering novel organisms and gaining new insights into microbially-mediated N transformations. Mathematical functions describing the earthworm-microbial relationships that contribute to nitrous oxide emissions from soils will be incorporated into predictive ecosystem-level models (DNDC, ecosys), which may eventually be used to calculate national greenhouse gas inventories with the IPCC Phase III methodology. In the next five years, this project will train 12 highly qualified personnel with specialized knowledge and analytical skills that are highly desired for research positions in the environmental sciences.