Exchange of important greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O) in forest ecosystems has traditionally focused on gas flux measurements between the soil and the atmosphere only. However, it has become evident that trees may play an important, and until recently overlooked, role in the net exchange of these GHGs. Trees can contribute to ecosystem exchange by uptake and transport of soil-produced CH4 and N2O to the atmosphere, in-situ production of both gases in plant tissues, and alternation of carbon- and nitrogen-turn-over in adjacent soil. However, the contribution of these individual processes to the net ecosystem GHGs exchange is still unclear and seems to depend on tree species, forest ecosystem type, environmental parameters and seasonal dynamics. Wetland tree species may be important CH4 sources, whereas some upland tree species are even known to be sinks for CH4. High N2O emissions have been particularly detected from trees grown under increased N2O concentrations in soils. The question thus remains whether mature trees exchange N2O with the atmosphere under low soil N2O concentration. First studies detected even N2O uptake by upland trees. Forests are also vulnerable to fire which itself is a poorly quantified source of especially CH4. This session seeks to bring together scientists working on the exchange of CH4 and N2O in forest ecosystems at any relevant scale, and from the full climatic and hydrological forest range. We therefore welcome contributions on microbial processes in soils, plant tissues and microtopographic forms, flux measurements on the forest floor, on cryptogams, on tree stems and at the leaf and canopy level; micrometeorological measurements using flux towers, and satellite, inverse and numerical modelling studies that seek to integrate our understanding of CH4 and N2O exchange in forest ecosystems.
Solicited speaker: Prof. Dr. Edzo Veldkamp, Georg-August-Universität Göttingen, Germany