Managing Moist Forests of the Pacific Northwest United States for Climate Positive Outcomes

Abstract

The moist forests of the Pacific Northwest United States (PNW) are among the most naturally carbon rich ecoregions in the world. However, regional in-forest carbon storage levels are currently well below ecological potential. Recent climate policy proposals have renewed and deepened debates over forest sector climate strategies. This paper begins with a review of regionally applicable forest carbon life cycle assessments (LCAs) in an effort to provide some clarity around how these studies are conducted, and why their results may vary. The review highlights the importance of assumptions made during carbon accounting across the wood product lifespan and how the inclusion or exclusions of variables, such as product substitution and leakage, influence study results and subsequent management recommendations. Next we discuss the influence of climate change on forest management and planning. We conclude with a review of regional-specific factors to consider when developing optimal forest climate strategies in the moist forests of the PNW. These strategies include, but are not limited to; extending harvest rotations, shelterwood and select tree harvests (in lieu of full harvest), and managing forests for increased structural, age, and species complexity.

Disturbance and management effects on forest soil organic carbon stocks in the Pacific Northwest

“…Our synthesis provides a clear distinction between management approaches from a C accounting perspective: in the context of widespread elevated fuel loads and chronically lagging reforestation efforts following fire (Cook‐Patton et al, 2020; Domke et al, 2020; Dumroese et al, 2019; Franklin & Johnson, 2012; Haugo et al, 2015), combinations of mechanical thinning and prescribed fire may be the most effective means to jointly minimize fire risk and SOC loss, especially in dry interior forests (Halofsky et al, 2020). Careful vegetation management can remove and utilize C from forests in a controlled fashion (Dugan et al, 2018; Fain et al, 2018; Malmsheimer et al, 2011) while protecting against uncontrolled losses of C from soils and biomass, even as rapid reforestation creates opportunities for C recovery and gain (Nave et al 2018; Nave, Walters et al, 2019). These findings will ideally inform strategic, regional discussions of C stewardship in forests of the Pacific Northwest.…”

Potential greenhouse gas reductions from Natural Climate Solutions in Oregon, USA

“…While we specifically model timber harvest deferral, altering other aspects of the timber harvest and wood processing system could also result in emission reductions [131]. In our study, we assume that 15% of the annual harvested wood volume results in unused mill residue or mill residue burned on site [50,51].…”

“…However, shifting wood product pools is unlikely to result in GHG emission reductions at the same order of magnitude as increasing rotation lengths and managing for older, more diverse forests [46,122,123]. Product substitution, which assumes the use of wood products materials in place of more emission intensive alternatives, has been treated variably in carbon accounting assessments [131]. While product substitution may provide GHG emission reductions, it is not included in our study due to the large and compounding uncertainty in assumptions related to estimating substitution [46,123].…”

More Timber in Construction: Unanswered Questions and Future Challenges

“…However, substitution has been labelled merely a theoretical carbon pool that is overestimated by some authors by an order of magnitude, and with a built-in double-counting mechanism that is initiated when the HWP is itself replaced [47]. Some models accumulate the benefits of substitution almost ad infinitum, whilst others define a more limited period of interest, such as 70 years [48].…”