Hotspots of soil N2O emission enhanced through water absorption by plant residue

N2O is a highly potent greenhouse gas and arable soils represent its major anthropogenic source. Field-scale assessments and predictions of soil N2O emission remain uncertain and imprecise due to the episodic and microscale nature of microbial N2O production, most of which occurs within very small discrete soil volumes. Such hotspots of N2O production are often associated with decomposing plant residue. Here we quantify physical and hydrological soil characteristics that lead to strikingly accelerated N2O emissions in plant residue-induced hotspots. Results reveal a mechanism for microscale N2O emissions: water absorption by plant residue that creates unique micro-environmental conditions, markedly different from those of the bulk soil. Moisture levels within plant residue exceeded those of bulk soil by 4–10-fold and led to accelerated N2O production via microbial denitrification. The presence of large (∅ >35 μm) pores was a prerequisite for maximized hotspot N2O production and for s...

一氧化二氮（N₂O）是一种强效温室气体，耕地土壤是其主要人为排放源。由于微生物产生N₂O具有间歇性和微尺度特性——其大部分过程发生在极小的离散土壤体积内，田间尺度土壤N₂O排放的评估与预测仍存在不确定性和不精确性。这类N₂O产生热点通常与分解中的植物残体相关。本研究量化了导致植物残体诱导热点中N₂O排放显著加速的土壤物理与水文特征。结果揭示了微尺度N₂O排放的一种机制：植物残体吸水形成独特的微环境条件，与主体土壤的环境特征存在显著差异。植物残体内的水分含量比主体土壤高4至10倍，并通过微生物反硝化作用（denitrification）加速N₂O的产生。大孔隙（直径>35 μm）的存在是热点区域N₂O产生最大化及s...的先决条件。