Flanagan Lawrence B, Nikkel Dylan J, Scherloski Lauren M, Tkach Rachel E, Smits Kristian M, Selinger L Brent, Rood Stewart B
Department of Biological Sciences, University of Lethbridge, 4401 University Drive, Lethbridge, AB, T1K 3M4, Canada.
Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, AB, T1K 3M4, Canada.
New Phytol. 2021 Feb;229(4):1970-1982. doi: 10.1111/nph.16977. Epub 2020 Oct 31.
Methane emission from trees may partially or completely offset the methane sink in upland soils, the only process that has been regularly included in methane budgets for forest ecosystems. Our objective was to analyze multiple biogeochemical processes that influence the production, oxidation and transport of methane in a riparian cottonwood ecosystem and its adjacent river. We combined chamber flux measurements on tree stems, forest soil and the river surface with eddy covariance measurements of methane net ecosystem exchange. In addition, we tested whether methanogens were present in cottonwood stems, shallow soil layers and alluvial groundwater. Average midday peak in net methane emission measured by eddy covariance was c. 12 nmol m s . The average uptake of methane by soils (0.87 nmol m s ) was largely offset by tree stem methane emission (0.75 nmol m s ). There was evidence of methanogens in tree stems but not in shallow soil. Growing season (May-September) cumulative net methane emission (17.4 mmol CH m ) included methane produced in cottonwood stems and methane input to the nocturnal boundary layer from the forest and the adjacent river. The multiple processes contributing to methane emission illustrated the linked nature of these adjacent terrestrial and aquatic ecosystems.
树木排放的甲烷可能会部分或完全抵消高地土壤中的甲烷汇，而高地土壤甲烷汇是森林生态系统甲烷收支中唯一经常被纳入的过程。我们的目标是分析影响河岸杨树林生态系统及其相邻河流中甲烷产生、氧化和传输的多个生物地球化学过程。我们将对树干、森林土壤和河流表面的箱式通量测量与甲烷净生态系统交换的涡度协方差测量相结合。此外，我们还测试了杨树树干、浅层土壤层和冲积层地下水中是否存在产甲烷菌。通过涡度协方差测量的甲烷净排放中午平均峰值约为12 nmol m⁻² s⁻¹。土壤对甲烷的平均吸收量（0.87 nmol m⁻² s⁻¹）在很大程度上被树干甲烷排放量（0.75 nmol m⁻² s⁻¹）抵消。有证据表明树干中存在产甲烷菌，但浅层土壤中没有。生长季节（5月至9月）累积净甲烷排放量（17.4 mmol CH₄ m⁻²）包括杨树树干中产生的甲烷以及森林和相邻河流向夜间边界层输入的甲烷。导致甲烷排放的多个过程说明了这些相邻陆地和水生生态系统的相互联系性质。
