Work

Tree stem-atmosphere greenhouse gas fluxes in a boreal riparian forest

Year: 2024

Type: article

Abstract: Tree stems exchange greenhouse gases with the atmosphere but the magnitude, variability and drivers of these fluxes remain poorly understood. Here, we report stem fluxes of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) in a boreal riparian forest , and investigate their spatiotemporal variability and ecosystem level importance. For two years, we measured CO 2 and CH 4 fluxes on a monthly basis in 14 spruces ( Picea abies ) and 14 birches ( Betula pendula ) growing near a headwater stream affected by historic ditching. We also measured N 2 O fluxes on three occasions. All tree stems were net emitters of CO 2 and CH 4 , while N 2 O fluxes were around zero. CO 2 fluxes correlated strongly with air temperature and peaked in summer. CH 4 fluxes correlated modestly with air temperature and solar radiation and peaked in late winter and summer. Trees with larger stem diameter emitted more CO 2 and less CH 4 and trees closer to the stream emitted more CO 2 and CH 4 . The CO 2 and CH 4 fluxes did not differ between spruce and birch, but correlations of CO 2 fluxes with stem diameter and distance to stream differed between the tree species. The absence of vertical trends in CO 2 and CH 4 fluxes along the stems and their low correlation with groundwater levels and soil CO 2 and CH 4 partial pressures suggest tree internal production as the primary source of stem emissions. At the ecosystem level, the stem CO 2 , CH 4 and N 2 O emissions represented 52 ± 16 % of the forest floor CO 2 emissions and 3 ± 1 % and 11 ± 40 % of the forest floor CH 4 and N 2 O uptake, respectively, during the snow-free period (median ± SE). The six month snow-cover period contributed 11 ± 45 % and 40 ± 29 % to annual stem CO 2 and CH 4 emissions, respectively. Overall, the stem gas fluxes were more typical for upland rather than wetland ecosystems likely due to historic ditching and subsequent groundwater level decrease.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2024.176243

Authors: Marcus Klaus, Mats Öquist, Kateřina Macháčová

Institutions: Swedish University of Agricultural Sciences, Czech Academy of Sciences, Global Change Research Institute

Language: English

Topic: Atmospheric and Environmental Gas Dynamics

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDGs: Climate action, Life on land

Open Access status: hybrid

Estimated APC paid: $3,990