Rice paddy soils are an important biogenic source of methane, a relevant greenhouse gas. Rice rotation with upland crops and pastures affects hydrolytic and fermentative bacteria and methanogenic archaea by sequential exposition to oxic and anoxic conditions. There are several ways to reduce methane emissions from rice paddy soils. Here we examine the effect of intensification in rice rotations with upland crops upon the microbial community structure and methanogenesis when dicarboxylic acids exudated by rice root were amended in microcosms assays. Soils under rotations rice-pasture, rice-soybean and continuous rice, with the last two more intensive systems recently installed in the field experiment, were sampled. Amplicon sequencing of 16S rRNA gene analysis showed that the rotation system was a main driver of the microbial community structure, explaining 33%, 38% and 55% of the differences in the structure of Bacteria, Archaea and methanogens, respectively. The density of mcrA gene copies was significantly higher in continuous rice soil than in other soils, and the relative abundance of methanogenic archaea was 33% for rice monoculture, whereas represented 15% and 14% for the rice-pasture and rice-soybean soils, respectively. The incubation of soils with tartrate and succinate confirmed functional differences among soils since rice monoculture showed similar or higher methane production and significantly less acetate and propionate accumulation than other soils. The T-RFLP analysis of mcrA gene in soils and incubated soils revealed that Rice Cluster I increased after incubation in all rotational soils, whereas Methanosarcinaceae and Methanobacteriaceae remained relevant after incubation. Furthermore, a more stable community of methanogenic archaea was established in soil under continuous rice, since T-RF profiles of soils and incubated soils with dicarboxylic acids grouped together with 62% similarity, while communities from other rotational soils experimented a great shift after incubation with these substrates. Altogether, these results showed that the conversion of rice-pasture rotational fields to a more intensive rice crop production strongly impacts the methanogenic community structure and their potential for methane emission.

稻田土壤是甲烷的重要生物来源，甲烷是一种相关的温室气体。水稻与旱地作物和牧场的轮作通过连续暴露于有氧和缺氧条件来影响水解和发酵细菌以及产甲烷古菌。有几种方法可以减少稻田土壤的甲烷排放。在这里，我们研究了在微观世界分析中修正水稻根部分泌的二羧酸时，水稻与旱作作物轮作对微生物群落结构和产甲烷的影响。对水稻-牧场、水稻-大豆和连续水稻轮作的土壤进行了采样，最近在田间试验中安装了最后两个更密集的系统。16S rRNA基因分析的扩增子测序表明，旋转系统是微生物群落结构的主要驱动力，分别解释了细菌、古生菌和产甲烷菌结构差异的 33%、38% 和 55%。的密度连续水稻土壤中的mcr A 基因拷贝数显着高于其他土壤，水稻单一栽培的产甲烷古菌相对丰度为 33%，而水稻-牧草和水稻-大豆土壤的产甲烷古菌相对丰度分别为 15% 和 14%。用酒石酸盐和琥珀酸盐培养土壤证实了土壤之间的功能差异，因为与其他土壤相比，水稻单一栽培显示出相似或更高的甲烷产量以及明显更少的乙酸盐和丙酸盐积累。土壤和孵化土壤中mcr A 基因的 T-RFLP 分析表明，在所有轮作土壤中孵化后，水稻簇 I 增加，而Methanosarcinaceae和Methanobacteriaceae孵化后仍然相关。此外，在连续水稻下的土壤中建立了一个更稳定的产甲烷古菌群落，因为土壤的 T-RF 剖面和用二羧酸培养的土壤具有 62% 的相似性，而来自其他轮作土壤的群落在用二羧酸培养后发生了很大的变化。这些基材。总之，这些结果表明，将稻草轮作田转变为更集约化的水稻作物生产强烈影响产甲烷群落结构及其甲烷排放潜力。