Synthesis Action 01

Until recently, it was believed that tree stem surfaces were inert to methane (CH₄) exchange with the atmosphere. However, technical advances in gas analysers for measuring CH₄ fluxes have shown that vegetation can contribute significantly to local and regional CH₄ budgets, with rates influenced by factors such as tree species, forest type, or environmental conditions. However, the global contribution of such fluxes is still under debate, with some estimates suggesting that tree fluxes should be considered as a new term in the global carbon (C) cycle. The novelty of this field of research and its potential implications for the global climate have led to a sharp increase in interest and the number of studies on CH₄ fluxes from trees over the last decade. As a community, we are at an exciting moment where we have sufficient understanding of the topic to frame the main challenges and future lines of research for the next decade, which include distinguishing between different CH₄ sources and sinks, biochemical processes, and gas transport mechanisms within the soil-plant-atmosphere system, that occur simultaneously on different time scales.