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，如以草和豆类为基础的干草地，支持着大量的蚯蚓种群，因为土壤不受耕作的干扰，而老化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，如地表和地下铸件(粪便颗粒)，蚊子(土壤表面的土壤-凋落物混合物)和洞穴很多。这些结构是微生物硝化菌和反硝化菌的有利栖息地，它们会产生一氧化二氮，这是一种强有力的温室气体，是它们新陈代谢的副产品。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，蚯蚓与微生物的相互作用导致小规模(微观世界、小块田地)一氧化二氮的产生，并可能导致农业生态系统层面的季节性一氧化二氮排放。这些生物相互作用将使用尖端研究工具进行评估，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稳定的同位素探测)。这些先进的技术极大地增加了我们发现新生物体的机会，并对微生物介导的N转化获得了新的见解。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的生态系统水平模型(DNDC、生态系统)，该模型最终可能被用于通过气专委第三阶段方法计算国家温室气体清单。在接下来的五年里，该项目将培训12名具有专门知识和分析技能的高素质人员，这些人员是环境科学研究职位所急需的。

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.