Data Sheet 2_Role of methanotrophic communities in atmospheric methane oxidation in paddy soils.xlsx

Wetland systems are known methane (CH4) sources. However, flooded rice fields are periodically drained. The paddy soils can absorb atmospheric CH4 during the dry seasons due to high-affinity methane-oxidizing bacteria (methanotroph). Atmospheric CH4 uptake can be induced during the low-affinity oxidation of high-concentration CH4 in paddy soils. Multiple interacting factors control atmospheric CH4 uptake in soil ecosystems. Broader biogeographical data are required to refine our understanding of the biotic and abiotic factors related to atmospheric CH4 uptake in paddy soils. Thus, here, we aimed to assess the high-affinity CH4 oxidation activity and explored the community composition of active atmospheric methanotrophs in nine geographically distinct Chinese paddy soils. Our findings demonstrated that high-affinity oxidation of 1.86 parts per million by volume (ppmv) CH4 was quickly induced after 10,000 ppmv high-concentration CH4 consumption by conventional methanotrophs. The ratios of 16S rRNA to rRNA genes (rDNA) for type II methanotrophs were higher than those for type I methanotrophs in all acid-neutral soils (excluding the alkaline soil) with high-affinity CH4 oxidation activity. Both the 16S rRNA:rDNA ratios of type II methanotrophs and the abundance of 13C-labeled type II methanotrophs positively correlated with high-affinity CH4 oxidation activity. Soil abiotic factors can regulate methanotrophic community composition and atmospheric CH4 uptake in paddy soils. High-affinity methane oxidation activity, as well as the abundance of type II methanotroph, negatively correlated with soil pH, while they positively correlated with soil nutrient availability (soil organic carbon, total nitrogen, and ammonium-nitrogen). Our results indicate the importance of type II methanotrophs and abiotic factors in atmospheric CH4 uptake in paddy soils. Our findings offer a broader biogeographical perspective on atmospheric CH4 uptake in paddy soils. This provides evidence that periodically drained paddy fields can serve as the dry-season CH4 sink. This study is anticipated to help in determining and devising greenhouse gas mitigation strategies through effective farm management in paddy fields.

湿地系统被视为甲烷（CH4）的来源。然而，水田在周期性排水。在干旱季节，由于高亲和力甲烷氧化菌（甲烷营养菌）的存在，稻田土壤可以吸收大气中的CH4。在大气CH4浓度较高的稻田土壤中，低亲和力氧化作用可以诱导大气CH4的吸收。多个相互作用的因素控制着土壤生态系统中的大气CH4吸收。为了更精确地理解与稻田土壤中大气CH4吸收相关的生物和非生物因素，需要更广泛的生物地理数据。因此，本研究旨在评估高亲和力CH4氧化活性，并探讨九个地理上不同的中国稻田土壤中活跃的大气甲烷营养菌群落组成。我们的研究结果表明，在传统甲烷营养菌消耗10,000 ppmv高浓度CH4之后，1.86 ppmv CH4的高亲和力氧化作用迅速被诱导。在所有具有高亲和力CH4氧化活性的酸性中性土壤中（排除碱性土壤），II型甲烷营养菌的16S rRNA与rRNA基因（rDNA）的比例高于I型甲烷营养菌。II型甲烷营养菌的16S rRNA:rDNA比例和13C标记的II型甲烷营养菌的丰度与高亲和力CH4氧化活性呈正相关。土壤非生物因素可以调节甲烷营养菌群落组成和稻田土壤中的大气CH4吸收。高亲和力甲烷氧化活性和II型甲烷营养菌的丰度与土壤pH值呈负相关，而与土壤养分供应（土壤有机碳、总氮和铵态氮）呈正相关。我们的研究结果强调了II型甲烷营养菌和非生物因素在稻田土壤中大气CH4吸收中的重要性。本研究为稻田土壤中大气CH4吸收提供了更广泛的生物地理视角。这为周期性排水的稻田可以作为干旱季节CH4汇提供了证据。本研究有望有助于通过有效的农场管理确定和制定温室气体减排策略。