The contribution of trees to ecosystem methane emissions in a temperate forested wetland
The contribution of trees to ecosystem methane emissions in a temperate forested wetland
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DOI：
10.1111/gcb.12891
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发表时间：
2015-07-01
影响因子：
11.6
通讯作者：
Gauci, Vincent
中科院分区：
文献类型：
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作者：
Pangala, Sunitha R.;Hornibrook, Edward R. C.;Gauci, Vincent
众所周知，适应湿地的树木可以将土壤产生的甲烷(CH4)输送到大气中，这是一种重要的温室气体，但对于成熟的森林来说，树木中介的CH4排放的季节变化和控制仍然未知。我们研究了位于温带森林湿地的两种湿地适应树种(赤杨和毛桦)干甲烷排放的时空变异性及其控制。还测量了土壤和草本植物从凹地和丘陵介导的CH4排放，从而能够估计每条途径对总生态系统通量的贡献。两种树种的树干CH4排放差异显著，其中粘杨表现出最小的季节变化，而毛桦表现出很大的季节变化。每种树的树干都会释放出类似数量的甲烷，无论它们是位于树洞还是丘陵地带。土壤温度和孔隙水CH4浓度最好地解释了树干排放的年际变化，而木材比密度和孔隙水CH4浓度最好地解释了树干CH4排放的树种间差异。我们的研究表明，在温带森林湿地，树木介导的CH4排放对季节生态系统CH4通量的贡献率高达27%，其中春季和冬季的相对贡献率最大。树木介导的CH4排放目前不包括在森林湿地的痕量气体收支中。需要进一步的工作来量化这一运输途径，并将其纳入甲烷清单和基于流程的模型。
Wetland-adapted trees are known to transport soil-produced methane (CH4), an important greenhouse gas to the atmosphere, yet seasonal variations and controls on the magnitude of tree-mediated CH4 emissions remain unknown for mature forests. We examined the spatial and temporal variability in stem CH4 emissions in situ and their controls in two wetland-adapted tree species (Alnus glutinosa and Betula pubescens) located in a temperate forested wetland. Soil and herbaceous plant-mediated CH4 emissions from hollows and hummocks also were measured, thus enabling an estimate of contributions from each pathway to total ecosystem flux. Stem CH4 emissions varied significantly between the two tree species, with Alnus glutinosa displaying minimal seasonal variations, while substantial seasonal variations were observed in Betula pubescens. Trees from each species emitted similar quantities of CH4 from their stems regardless of whether they were situated in hollows or hummocks. Soil temperature and pore-water CH4 concentrations best explained annual variability in stem emissions, while wood-specific density and pore-water CH4 concentrations best accounted for between-species variations in stem CH4 emission. Our study demonstrates that tree-mediated CH4 emissions contribute up to 27% of seasonal ecosystem CH4 flux in temperate forested wetland, with the largest relative contributions occurring in spring and winter. Tree-mediated CH4 emissions currently are not included in trace gas budgets of forested wetland. Further work is required to quantify and integrate this transport pathway into CH4 inventories and process-based models.