Methane emissions from tree stems: a new frontier in the global carbon cycle

• Published in: The New phytologist Vol. 222; no. 1
• Main Authors: Barba, Josep, Bradford, Mark A., Brewer, Paul E., Bruhn, Dan, Covey, Kristofer, Haren, Joost, Megonigal, J. Patrick, Mikkelsen, Teis Nørgaard, Pangala, Sunitha R., Pihlatie, Mari, Poulter, Ben, Rivas‐Ubach, Albert, Schadt, Christopher W., Terazawa, Kazuhiko, Warner, Daniel L., Zhang, Zhen, Vargas, Rodrigo
• Format: Journal Article
• Language: English
• Published: United States Wiley 18-12-2018
• Subjects: methane emissions, CH4, tree stems, upland forests, wetland forests, methanogenesis, spatial variability, temporal variability
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.15582

Tree stems from wetland, floodplain and upland forests can emit CH4. This emerging field of research has revealed a high spatial and temporal variability on CH4 stem emissions between trees and species, and within and across ecosystems, which is not completely understood. Additionally, there is no consensus on the biophysical mechanisms that could support stem CH4 emissions, including the origin of these emissions. This hinders our understanding of spatial and temporal patterns and hamper the identification of biophysical drivers. Here, we summarize up to 30 opportunities and challenges on stem CH4 emissions research in order to improve estimates of magnitudes, patterns, drivers and trace the potential origin of CH4 emissions. We propose two main challenges: the need for long-term high frequency measurements of stem CH4 emissions, and the need for a mechanistic model including passive and active transport of CH4 from the soil-tree-atmosphere continuum. The first challenge would allow to constrain magnitudes and patterns of CH4 emissions at different temporal scales, and the second would require discovery and integration of pathways and mechanisms of CH4 production and emissions to be integrated into process-base models. Addressing these challenges might improve upscaling of CH4 emissions from trees to the ecosystem scale and the quantification of the role of stem CH4 emissions for the local-to-global CH4 budget.