4:00 PM - 4:15 PM
[ACG37-09] Accounting for the emissions of tree stems in the methane budget of forests: upscaling chamber measurements to the stand
Keywords:Methane, Forest, Upscaling
Forests are a well-known carbon sink, which mitigate the rise in atmospheric CO2 and hence global warming. However, methane emissions by stems of living trees become a major concern due to the increasing contribution of methane to global warming. Indeed, methane is the second most important anthropogenic greenhouse gas. Until now, global and regional methane budgets of forests, which cover one third of the land area (67% in Japan) have only considered the source and sink functions of soils, ignoring stem emissions. However, there are growing evidences that trees emit methane through their stem, and the role of trees, in addition to that of the soil, must be considered in the methane budget of forests.
Our objective was to evaluate how to upscale stem CH4 emissions to the ecosystem level and a prerequisite was first to understand the variability of stem CH4 emissions across individuals and species, and within individuals: does tree size influence stem CH4 emission and how do these emissions vary spatially along the stem?
Measurements were carried out in the Ashiu experimental forest from August to December on two to three trees per species and two positions along the trunk. The trunk of five major species at this site emitted CH4, with a large variability among species. While the temporal variation was low (both diurnal and day to day), CH4 emission were higher for large trees than smaller ones for a given species and varied with the position along the trunk.
We have used these preliminary results to provide an estimate of the CH4 emission from the whole trees and we present avenues for estimating these emissions at the stand level considering tree species diversity (contribution of the main species) and the stand structural attributes (tree diameter and height), using species-species allometric relations.
Our objective was to evaluate how to upscale stem CH4 emissions to the ecosystem level and a prerequisite was first to understand the variability of stem CH4 emissions across individuals and species, and within individuals: does tree size influence stem CH4 emission and how do these emissions vary spatially along the stem?
Measurements were carried out in the Ashiu experimental forest from August to December on two to three trees per species and two positions along the trunk. The trunk of five major species at this site emitted CH4, with a large variability among species. While the temporal variation was low (both diurnal and day to day), CH4 emission were higher for large trees than smaller ones for a given species and varied with the position along the trunk.
We have used these preliminary results to provide an estimate of the CH4 emission from the whole trees and we present avenues for estimating these emissions at the stand level considering tree species diversity (contribution of the main species) and the stand structural attributes (tree diameter and height), using species-species allometric relations.