Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests.
Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests.
复制标题
亚热带低地森林内轴向树干甲烷氧化的同位素证据。
作者：
Luke C. Jeffrey;D. Maher;D. Tait;Michael J. Reading;E. Chiri;C. Greening;S. Johnston
关于减缓甲烷（CH 4）汇/源行为沿着沉积物-树干-大气连续体的机制的知识仍然不完整。在这里，我们应用稳定同位素分析（δ13 C-CH 4），以获得洞察轴向CH 4运输和氧化在两个全球分布的亚热带低地物种（白千层五脉和木麻黄glauca）。结果表明，CH 4通量（随高度的增加而减少）和δ13 C-CH 4富集（随高度的增加而增加）与树干离地高度的关系是一致的。白千层和木麻黄树干下部0-40 cm的δ13 C-CH 4平均值（-53.96 ‰和-65.89 ‰）与相邻的淹水沉积物CH 4沸腾值（-52.87 ‰和-62.98 ‰）相似，表明树干CH 4主要来源于土壤。81-200 cm的树干上部δ13 C-CH 4明显富集，白千层为-44.6 ‰，木麻黄为-46.5 ‰。耦合3D摄影测量与新的3D干测量显示不同的热点CH 4通量和同位素分馏白千层，可能是由于树皮异常的气体流出的优先途径增强。昼夜实验表明，相对于上午，下午更大的δ13 C-CH 4富集和更高的氧化速率。总的来说，我们估计，约33%的甲烷在轴向运输过程中在上下茎之间被氧化，因此可能代表了一个全球性的，但以前未考虑的甲烷汇。
Knowledge regarding mechanisms moderating methane (CH4 ) sink/source behaviour along the sediment-tree stem-atmosphere continuum remains incomplete. Here, we applied stable isotope analysis (δ13 C-CH4 ) to gain insights into axial CH4 transport and oxidation in two globally distributed subtropical lowland species (Melaleuca quinquenervia and Casuarina glauca). We found consistent trends in CH4 flux (decreasing with height) and δ13 C-CH4 enrichment (increasing with height) in relation to stem height from ground. The average lower tree stem δ13 C-CH4 (0-40 cm) of Melaleuca and Casuarina (-53.96 ‰ and -65.89 ‰) were similar to adjacent flooded sediment CH4 ebullition (-52.87 ‰ and -62.98 ‰), suggesting that stem CH4 is derived mainly via soil sources. Upper stems (81-200 cm) displayed distinct δ13 C-CH4 enrichment (Melaleuca -44.6 ‰ and Casuarina -46.5 ‰ respectively). Coupled 3D-photogrammetry with novel 3D-stem measurements revealed distinct hotspots of CH4 flux and isotopic fractionation on Melaleuca, were likely due to bark anomalies where preferential pathways of gas efflux were enhanced. Diel experiments revealed greater δ13 C-CH4 enrichment and higher oxidation rates in the afternoon, relative to the morning. Overall, we estimated that ~33% of the methane was oxidised between lower and upper stems during axial transport, thus potentially representing a globally significant, yet previously unaccounted for, methane sink.
影响因子：
4.6
作者：
Barba, Josep;Poyatos, Rafael;Vargas, Rodrigo
通讯作者：
Vargas, Rodrigo