Riparian cottonwood trees and adjacent river sediments have different microbial communities and produce methane with contrasting carbon isotope compositions

Rivers and their adjacent riparian forests are intimately linked by the exchange of water, nutrients, and organic matter. Both riparian cottonwood trees and adjacent river sediments host microbial communities including archaeal methanogens, supporting methane production and emission to the atmosphere. Here we combine microbial community and stable isotope analyses to characterize the drivers of methane cycling in distinct anoxic habitats (river sediments versus riparian cottonwood stems) in the Oldman River, southern Alberta (Canada). We demonstrate that, differences in the chemical characteristics of organic matter support divergent microbial communities that generate methane from distinct metabolic pathways. Organic matter in river sediments had C/N ratios approximately 50-fold lower than in tree stems and had more diverse dissolved organic components. Contrasting substrate availability between river sediment and tree stems was likely the primary mechanism for the observed differences...

河流与毗邻的河岸森林通过水分、营养物质与有机质的交换紧密联结。河岸杨木（riparian cottonwood trees）与相邻河流沉积物均定殖有包括产甲烷古菌（archaeal methanogens）在内的微生物群落，支撑甲烷的产生与向大气的排放。本研究结合微生物群落分析与稳定同位素分析（stable isotope analyses），对加拿大阿尔伯塔省南部奥尔德曼河（Oldman River）中两类不同缺氧生境——河流沉积物与河岸杨木茎干——的甲烷循环驱动因子进行表征。研究表明，有机质的化学性质差异造就了截然不同的微生物群落，二者通过不同代谢途径产生甲烷。河流沉积物中的有机质碳氮比（C/N ratios）较杨木茎干低约50倍，且溶解有机质组分更为多样。河流沉积物与杨木茎干之间底物可获得性的显著差异，可能是观测到的群落差异的主要成因……