Paddy fields differ greatly in their soil historical water regimes, which in turn vary substrate availability and assembly of methanogenic communities for methane (CH) production. However, it remains unclear how the response of the methanogenesis process to current soil moisture is impacted by past water regimes. Here, we noticed that the composition of the methanogenic community was influenced much more by long-term water management practices than by short-term soil moisture changes. Methanogenesis in a permanent flooding system [rice-fallow (RF) with 70–80% historical soil volumetric moisture content (SVMC)] exhibited a higher positive response to moisture variation compared to the alternating aerobic-anaerobic conditions [ricewheat (RW) and double-rice (DR) with 30–50% historical SVMC]. Although the soil CH production potential (MPP) from these systems increased with increasing current moisture levels (water:soil ratios of 0.5, 0.75, 1, and 1.5), it was more sensitive to moisture changes in RF soil than in RW and DR soils. This increase in MPP was probably due to the enhanced available dissolved organic carbon with moisture promotion. Moreover, the relative contribution of acetoclastic methanogenesis () significantly increased from approximately 70% to 80% in the RF soil ( < 0.05) when the moisture rose from 0.5 to 1.5. Structural equation modelling analysis showed that this change was mainly ascribed to the simultaneous increase in acetate content. In contrast, the values under the four moisture contents were relatively stable at approximately 50% and 65% in RW and DR soils, respectively. The abundance of acetoclastic was far higher in RF soil than in RW and DR soils, which was possibly the reason for the larger values. The findings indicate that methanogenesis in high historical SVMC was more sensitive to the current moisture regulation and further suggest that its CH production reduction via drainage was mainly due to the decline in acetate-dependent methanogenesis.

中文翻译：

---

历史水情决定了产甲烷途径对当前土水比的响应

稻田的土壤历史水分状况差异很大，这反过来又改变了底物的可用性和甲烷（CH）生产的产甲烷群落的组装。然而，目前尚不清楚产甲烷过程对当前土壤湿度的响应如何受到过去水情的影响。在这里，我们注意到，长期水管理实践对产甲烷群落的组成的影响比短期土壤湿度变化的影响更大。与交替有氧-厌氧条件[稻麦(RW)和双氧条件]相比，永久淹水系统[水稻休耕(RF)，历史土壤体积含水量(SVMC)]中的产甲烷作用对水分变化表现出更高的正响应。 -具有 30-50% 历史 SVMC 的大米 (DR)]。尽管这些系统的土壤 CH 生产潜力 (MPP) 随着当前湿度水平的增加而增加（水土比为 0.5、0.75、1 和 1.5），但与 RW 和 DR 土壤相比，RF 土壤对湿度变化更敏感。MPP 的增加可能是由于水分促进下有效溶解有机碳的增加。此外，当湿度从 0.5 升至 1.5 时，RF 土壤 (< 0.05) 中乙酰分解产甲烷的相对贡献 () 显着从约 70% 增加至 80%。结构方程模型分析表明，这种变化主要归因于醋酸盐含量的同时增加。相比之下，RW 和 DR 土壤中四种含水量下的值相对稳定，分别约为 50% 和 65%。RF 土壤中醋酸碎屑的丰度远高于 RW 和 DR 土壤，这可能是数值较大的原因。研究结果表明，高历史SVMC中的产甲烷作用对当前的水分调节更加敏感，并进一步表明其通过排水而产生的CH产量减少主要是由于乙酸盐依赖性产甲烷作用的下降。