Impacts of Clear-Cutting of a Boreal Forest on Carbon Dioxide, Methane and Nitrous Oxide Fluxes

Abstract

The 2015 Paris Agreement encourages stakeholders to implement sustainable forest management policies to mitigate anthropogenic emissions of greenhouse gases (GHG). The net effects of forest management on the climate and the environment are, however, still not completely understood, partially as a result of a lack of long-term measurements of GHG fluxes in managed forests. During the period 2010–2013, we simultaneously measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes using the flux-gradient technique at two clear-cut plots of different degrees of wetness, located in central Sweden. The measurements started approx. one year after clear-cutting, directly following soil scarification and planting. The study focused on robust inter-plot comparisons, spatial and temporal dynamics of GHG fluxes, and the determination of the global warming potential of a clear-cut boreal forest. The clear-cutting resulted in significant emissions of GHGs at both the wet and the dry plot. The degree of wetness determined, directly or indirectly, the relative contribution of each GHG to the total budgets. Faster establishment of vegetation on the wet plot reduced total emissions of CO2 as compared to the dry plot but this was partially offset by higher CH4 emissions. Waterlogging following clear-cutting likely caused both plots to switch from sinks to sources of CH4. In addition, there were periods with N2O uptake at the wet plot, although both plots were net sources of N2O on an annual basis. We observed clear diel patters in CO2, CH4 and N2O fluxes during the growing season at both plots, with the exception of CH4 at the dry plot. The total three-year carbon budgets were 4107 gCO2-equivalent m−2 and 5274 gCO2-equivalent m−2 at the wet and the dry plots, respectively. CO2 contributed 91.8% to the total carbon budget at the wet plot and 98.2% at the dry plot. For the only full year with N2O measurements, the total GHG budgets were 1069.9 gCO2-eqvivalents m−2 and 1695.7 gCO2-eqvivalents m−2 at the wet and dry plot, respectively. At the wet plot, CH4 contributed 3.7%, while N2O contributed 7.3%. At the dry plot, CH4 and N2O contributed 1.5% and 7.6%, respectively. Our results emphasize the importance of considering the effects of the three GHGs on the climate for any forest management policy aiming at enhancing the mitigation potential of forests.

Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management

“…Clear‐cutting in boreal forests (not after fire) can turn forest soils from sinks to sources of CH 4 due to reductions in evapotranspiration and consequent increases in the water table (Sundqvist et al, 2014; Vestin et al, 2020) or soil compaction by heavy machinery (Strömgren et al, 2016; Teepe et al, 2004). However, we found no significant differences in SWC between the SHM and HM sites, and we did not observe any evidence of soil compaction at the SHM site.…”

The short-term effect of partial harvesting and clearcutting on greenhouse gas fluxes and evapotranspiration in a nutrient-rich peatland forest

“…12 and 13). Similar results of the soil turning from a CH4 sink to a source after clearcutting have been found on both peat (Zerva and Mencuccini, 2005) and mineral soil (Castro et al, 2000;Vestin et al, 2020) soil, which were attributed to increases in WTL and soil moisture. However, opposing results have also been observed on both soil types.…”

“…Large CO2 emissions have been measured for several years after clearcutting upland forests (Amiro et al, 2010;. Also, the net CH4 Vestin et al, 2020) and N2O emissions have been observed to increase, even though the research is not as comprehensive as with CO2. These environmental and economic problems have raised a discussion if continuous cover forestry (CCF) could be a feasible alternative to EM in peatland forests .…”

Back to the Future: Restoring Northern Drained Forested Peatlands for Climate Change Mitigation

“…Water table variability is likely higher than in the pristine state because lower soil macroporosity and higher bulk density developed after long term drainage have a negative effect on hydraulic conductivity and water storage capacity (Ahmad et al, 2020;Liu et al, 2020;Kreyling et al, 2021). High organic substrate availability is expected due to rewetting associated disturbances, tree residues, turnover of tree roots and its associated microbial biomass and expansion of wetland vascular plants (Rigney et al, 2018;Vestin et al, 2020). High nutrient availability due to low plant nutrient demand is expected which, added to rewetting associated disturbances, might promote high nutrients exports often reported after rewetting (Koskinen et al, 2017;Nieminen et al, 2020).…”