Journal Article

Methane exchange in a boreal forest estimated by gradient method

Lindroth, Anders, Mölder, Meelis, Kljun, Natascha, Crill, Patrick, Sundqvist, Elin

2015

Overview

Forests are generally considered to be net sinks of atmospheric methane (CH 4 ) because of oxidation by methanotrophic bacteria in well-aerated forests soils. However, emissions from wet forest soils, and sometimes canopy fluxes, are often neglected when quantifying the CH 4 budget of a forest. We used a modified Bowen ratio method and combined eddy covariance and gradient methods to estimate net CH 4 exchange at a boreal forest site in central Sweden. Results indicate that the site is a net source of CH 4 . This is in contrast to soil, branch and leaf chamber measurements of uptake of CH 4 . Wetter soils within the footprint of the canopy are thought to be responsible for the discrepancy. We found no evidence for canopy emissions per se. However, the diel pattern of the CH 4 exchange with minimum emissions at daytime correlated well with gross primary production, which supports an uptake in the canopy. More distant source areas could also contribute to the diel pattern; their contribution might be greater at night during stable boundary layer conditions.

• Publisher: Taylor & Francis,Stockholm University Press
• Subject: Boreal forests / Bowen ratio / Earth and Related Environmental Sciences / eddy covariance / footprint / Forests / Geovetenskap och relaterad miljövetenskap / Methane / Methods / micrometeorology / Natural Sciences / Naturvetenskap / Saturated soils / Science / Soil depth / Soil moisture / Soil texture / Water depth / Water table / wet soil