Department of Microbiology, University of Massachusetts Amherst, Amherst, MA, USA.
Bioenergy and Biome Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA.
ISME J. 2021 Mar;15(3):658-672. doi: 10.1038/s41396-020-00804-x. Epub 2020 Oct 20.
The Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink threatened by agricultural conversion. Rainforest-to-pasture conversion stimulates the release of methane, a potent greenhouse gas. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active methanogens in pastures. We conclude that a significant increase in the abundance and activity of methanogens in pasture soils could drive increased soil methane emissions. Furthermore, we found that secondary rainforests had decreased methanogenic activity similar to primary rainforests, and thus a potential to recover as methane sinks, making it conceivable for forest restoration to offset greenhouse gas emissions in the tropics. These findings are critical for informing land management practices and global tropical rainforest conservation.
亚马逊雨林是生物多样性热点地区和大型陆地碳汇，但其正受到农业转化的威胁。从雨林到牧场的转化会刺激甲烷的释放，而甲烷是一种强大的温室气体。生物甲烷循环由微生物驱动；因此，本研究专注于活跃的甲烷循环微生物及其在不同土地利用类型中的功能。我们从巴西亚马逊地区的两个地理位置（帕拉州的圣塔伦和朗多尼亚州的阿里克米斯）的三种土地利用类型（原始雨林、牧场和次生雨林）中收集完整的土壤芯，并进行 DNA 稳定同位素探针与宏基因组学相结合，以鉴定活跃的甲烷营养菌和产甲烷菌。在这两个地点，我们观察到，在土地利用类型之间，同位素标记的甲烷循环微生物群落的组成发生了显著变化，特别是在牧场上，产甲烷菌的丰度和多样性显著增加。我们得出结论，牧场上产甲烷菌的丰度和活性的显著增加可能会导致土壤甲烷排放量的增加。此外，我们发现次生雨林的产甲烷活性与原始雨林相似，因此有潜力恢复为甲烷汇，从而使森林恢复能够抵消热带地区的温室气体排放。这些发现对于为土地管理实践和全球热带雨林保护提供信息至关重要。
