Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality.

Here we provide the raw data from our publication in New Phytologist (accepted 10 June 2019). Out study highlights are as follows: • Growing evidence indicates tree-stem methane emissions may be an important and un-accounted for component of local, regional and global carbon budgets. Studies to date have focussed on upland and freshwater swamp-forests; however, no data on tree-stem fluxes from estuarine species currently exist. • Here we provide the first-ever mangrove tree-stem methane flux measurements from >50 trees (n=230 measurements), in both standing dead and living forest, from a region suffering a recent large-scale climate-driven dieback event (Gulf of Carpentaria, Australia). • Average methane emissions from standing dead mangrove tree-stems were 249.2 ± 41.0 µmol m-2 d-1 and eight-fold higher than from living mangrove tree-stems (37.5 ± 5.8 µmol m-2 d-1). The average methane flux from tree-stem bases (~10cm above ground) was 1071.1 ± 210.4 µmol m-2 d-1 and 96.8 ± 27.7 µmol m-2 d-1 from dead and living stands respectively. Sediment methane fluxes and redox potentials did not differ significantly between living and dead stands. Our results suggest both dead and living tree-stems act as methane conduits to the atmosphere, bypassing potential sedimentary oxidation processes. • Although large uncertainties exist when up-scaling data from small-scale temporal measurements, we estimated that dead mangrove tree-stem emissions may account for ~26 % of the net ecosystem methane flux.

我们在此提供发表于《新植物学家》（New Phytologist，2019年6月10日接收）的研究原始数据。本研究亮点如下：• 越来越多的证据表明，树干甲烷排放可能是局域、区域及全球碳收支中一个重要且未被充分考虑的组成部分。迄今为止的研究主要集中于山地和淡水沼泽森林；然而，目前尚无关于河口物种树干通量的数据。• 我们在此提供首次针对超过50棵树（n=230次测量）的红树林树干甲烷通量数据，样本来自近期受气候驱动发生大规模枯死事件的区域（澳大利亚卡奔塔利亚湾）的活林和枯立木林。• 红树林枯立木树干的平均甲烷排放量为249.2 ±41.0 µmol m⁻² d⁻¹，是活树树干（37.5 ±5.8 µmol m⁻² d⁻¹）的8倍。树干基部（地面以上约10cm处）的平均甲烷通量在枯立木林和活林中分别为1071.1 ±210.4 µmol m⁻² d⁻¹和96.8 ±27.7 µmol m⁻² d⁻¹。活林与枯立木林之间的沉积物甲烷通量和氧化还原电位无显著差异。研究结果表明，枯立木和活树的树干均作为甲烷向大气传输的通道，绕过了潜在的沉积物氧化过程。• 尽管从小尺度时间测量数据外推时存在较大不确定性，但我们估算枯立木红树林树干排放可能占生态系统净甲烷通量的约26%。