Ageing forests and carbon storage: a case study in boreal balsam fir stands

Abstract

The pattern of change in carbon (C) accumulation with forest ageing can vary greatly amongst different forest types. Documenting how C accumulates in various forest ecosystems in the absence of logging makes it possible to predict what would be the outcome of extending forest rotations or in dedicating more land to conservation on C storage. This study was conducted in boreal balsam fir (Abies balsamea (L.) Mill.) forests of Quebec, in eastern Canada. We compared carbon stocks in forest pools (aboveground (live) biomass, deadwood, FH horizon and mineral soil) of mature (70 years after harvest) vs old-growth stands (stands with no signs or history of human disturbance). Total ecosystem C stocks were not significantly different between mature and old-growth stands. However, as mature stands transition to old-growth stage, there appears to be a shift of C from live biomass pools towards deadwood and soil FH horizons. Coarse woody debris in old-growth stands were also found to be at more advanced stages of decay. The variability of C stocks was also high amongst old-growth stands; however, there was no obvious difference in structural diversity between mature and old-growth stands. Results suggest that ageing balsam fir stands through the lengthening of forest rotations (e.g. past the maturity age of 70 years) or by placing them under conservation, while not creating an important C sink, still contributes to maintain large forest C stocks across landscapes. Preserving or increasing the presence of old-growth forests is an important aspect of ecosystem-based forest management; our study concludes that it could also be compatible with sustainable forest carbon management.

Aboveground live tree carbon stock and change in forests of conterminous United States: influence of stand age

“…The pattern of increasing carbon stocks with stand age (Table 1 , Additional file 1 : Table S1 and Additional file 4 : Table S4), followed by a leveling off or slight decline, is as expected and widely reported (e.g., [ 28 , 17 , 29 ]). Most regions in the United States follow the pattern of increasing stock (with occasional declines in the oldest age classes) and decreasing rate as stand age increases (Fig.…”

Under what circumstances can the forest sector contribute to 2050 climate change mitigation targets? A study from forest ecosystems to landfill methane emissions for the province of Quebec, Canada

“…Strategies that involve reducing the annual harvested volume might be more at risk of carbon inversion caused by natural disturbances due to the abundance of mature and old‐growth forests that such strategies create (Sharma et al, 2013). The significant uncertainty related to the carbon sink capacity of those stands over the long term (Gao et al, 2018; Gundersen et al, 2021; Smyth et al, 2020) may also be a concern, as ecosystem carbon stocks may eventually become saturated (Harel et al, 2021). Yet, uncertainty regarding the net carbon sink potential of mature and old‐growth stands should not overshadow their role as carbon reservoirs (Harel et al, 2021).…”

“…The significant uncertainty related to the carbon sink capacity of those stands over the long term (Gao et al, 2018; Gundersen et al, 2021; Smyth et al, 2020) may also be a concern, as ecosystem carbon stocks may eventually become saturated (Harel et al, 2021). Yet, uncertainty regarding the net carbon sink potential of mature and old‐growth stands should not overshadow their role as carbon reservoirs (Harel et al, 2021). On the other hand, expected changes in natural disturbance regimes could negatively impact the productivity and regeneration capacity of forest ecosystems (Boulanger et al, 2017) and thus jeopardize the sustainability of wood production (Bouchard et al, 2022; Boucher et al, 2018; Brecka et al, 2020).…”

A regional integrated assessment of the impacts of climate change and of the potential adaptation avenues for Quebec's forests

“…Moreover, there are still uncertainties regarding the ability of these stands to act as carbon sinks in the long term (Gao et al 2018, Smyth et al 2020, Gundersen et al 2021) as conservation after age 70 does not result in significant carbon uptake or emission in Quebec's boreal forests (Harel et al 2021). That being said, we advocate that these uncertainties should not overshadow the role of old-growth forests to act as carbon sinks (Harel et al 2021).…”

“…For instance, conservation strategies that maintain or increase the abundance of mature and old-growth forests might be more at risk of carbon inversion in landscapes that are more prone to natural disturbances (Sharma et al 2013). Moreover, there are still uncertainties regarding the ability of these stands to act as carbon sinks in the long term (Gao et al 2018, Smyth et al 2020, Gundersen et al 2021) as conservation after age 70 does not result in significant carbon uptake or emission in Quebec's boreal forests (Harel et al 2021). That being said, we advocate that these uncertainties should not overshadow the role of old-growth forests to act as carbon sinks (Harel et al 2021).…”