Methanogenic Archaea dominate mature heartwood habitats of Eastern Cottonwood (Populus deltoides)

First author: Daniel Z. Yip; Affiliations: Oak Ridge National Laboratory (橡树岭国家实验室): Oak Ridge, USA

Corresponding author: Christopher W. Schadt

While recent reports demonstrate that the direct emission of methane (甲烷) from living tree trunks may be a significant terrestrial emission source, there has been debate whether tree emissions are due to transport from soils or produced in the wood environment itself. Reports of methanogens (产甲烷菌) from wood of trees were prominent in the literature 40 years ago but have not been revisited with molecular ecology approaches. We examined communities associated with Populus deltoides (美洲黑杨) using rRNA gene sequence analyses and how these vary with tree and wood properties. Our data indicate that wood environments are dominated by anaerobic microbiomes (厌氧微生物群落). Methanogens are prominent in heartwood (mean 34% relative abundance) compared to sapwood (边材) environments (13%), and dominant operational taxonomic units (OTUs; 操作分类单元) were classified as the Methanobacterium sp. Members of the Firmicutes phylum (厚壁菌门) comprised 39% of total sequences and were in 42% greater abundance in sapwood over heartwood niches. Tree diameter was the strongest predictor of methanogen abundance, but wood moisture content (含水量) and pH were also significant predictors of taxon abundance and overall community composition. Unlike microbiomes of the soil, rhizosphere (根际) and phyllosphere (叶际), wood associated communities are shaped by unique environmental conditions and may be prominent and overlooked (被忽视的) sources of methane emissions in temperate forest systems.

尽管近来有研究表明林木躯干中直接释放的甲烷可能是陆地甲烷释放的一个重要来源，然而林木释放甲烷是来自于土壤的转运还是源自于林木自身还未可知。近40年来的研究显示林木木材中的产甲烷菌是主要的甲烷释放来源，然而并为有研究通过分子生态学的方法进行过验证。本文在美洲黑杨中通过rRNA基因测序研究了微生物群落的组成，并研究了其在不同林木与木材材性中的变异。本文的实验数据显示林木木材环境中主要是厌氧微生物群落。相对于边材中产甲烷菌占13%，在心材中产甲烷菌占主要部分，占比34%，并且主要的操作分类单元OTU分类为厚壁菌门的甲烷杆菌属，占了所有序列中的39%，边材中的含量要比心材中高出42%。林木直径与甲烷菌的丰度显著相关，同时木材含水量和pH值与微生物种类丰度及总体微生物群落组成呈显著相关。与土壤、根际和叶际微生物不同，木材相关的微生物群落受到独特的环境调控塑造，且可能是温带森林系统中甲烷释放的未被重视的主要来源。

通讯：Christopher W. Schadt (https://climatechangescience.ornl.gov/content/christopher-w-schadt)

个人简介：2002年，科罗拉多大学，博士。

doi: https://doi.org/10.1111/nph.15346

Journal: New Phytologist

First Published: 06 July, 2018

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