Applying climate change refugia to forest management and old‐growth restoration

Abstract

Recent studies highlight the potential of climate change refugia (CCR) to support the persistence of biodiversity in regions that may otherwise become unsuitable with climate change. However, a key challenge in using CCR for climate resilient management lies in how CCR may intersect with existing forest management strategies, and subsequently influence how landscapes buffer species from negative impacts of warming climate. We address this challenge in temperate coastal forests of the Pacific Northwestern United States, where declines in the extent of latesuccessional forests have prompted efforts to restore old-growth forest structure.One common approach for doing so involves selectively thinning forest stands to enhance structural complexity. However, dense canopy is a key forest feature moderating understory microclimate and potentially buffering organisms from climate change impacts, raising the possibility that approaches for managing forests for old-growth structure may reduce the extent and number of CCR. We used remotely sensed vegetation indices to identify CCR in an experimental forest with control and thinned (restoration) treatments, and explored the influence of biophysical variables on buffering capacity. We found that remotely sensed vegetation indices commonly used to identify CCR were associated with understory temperature and plant community composition, and thus captured aspects of landscape buffering that might instill climate resilience and be of interest to management. We then examined the interaction between current restoration strategies and CCR, and found that selective thinning for promoting old-growth structure had only very minor, if any, effects on climatic buffering. In all, our study demonstrates that forest management approaches aimed at restoring old-growth structure through targeted thinning do not greatly decrease buffering capacity, despite a known link between dense canopy and CCR. More broadly, this study illustrates the value of using remote sensing approaches to identify CCR, facilitating the integration of climate change adaptation with other forest management approaches.

Forest restoration thinning accelerates development of old‐growth characteristics in the coastal Pacific Northwest,USA

“…Increased species diversity has been identified as a method to increase community resilience (Tilman, 1999) and can provide additional habitat and forage opportunities for a diversity of species (Stein et al, 2013). A diversity of habitats and food may become increasingly important as animal species move in response to warming temperatures and changes in moisture regimes (Littlefield et al, 2019;Pradhan et al, 2023).…”

“…Climate change also impacts vegetation dynamics, growth, mortality, and regeneration and therefore, long-term monitoring (i.e., dendrochronology, climate monitoring, tree-water relationships, and insect and disease monitoring), and subsequent analyses are needed to determine the successional pathway and assess whether restoration objectives are continually being met (Reilly & Spies, 2015). Future research could also integrate our empirical results with modeling studies to further assess and prioritize restoration treatment effects aimed at accelerating old-growth forest characteristics, enhancing wildlife habitat, and increasing climate change resilience (e.g., Pradhan et al, 2023). Further, our results could be combined with other research studies in a meta-analysis to better understand the multiple spatial, temporal, and population effects of restoration treatments.…”

Refuge‐yeah or refuge‐nah? Predicting locations of forest resistance and recruitment in a fiery world

“…The explicit incorporation of fire refugia into the planning of such strategies is new, yet promising (Krawchuk et al, 2020; Martinez et al, 2019; Stevens et al, 2021). For example, locations of potential refugia might be used to conserve habitat and maintain connectivity for fire‐sensitive species (Andrus et al, 2021; Landesmann & Morales, 2018; Robinson et al, 2014) or considered as essential elements that influence the outcomes of larger fuel treatments (Pradhan et al, 2023; Wilkin et al, 2016). After over a century of fire exclusion, fire is now regarded as a key tool to promote resilient social‐ecological systems (North et al, 2021; Schoennagel et al, 2017).…”

Variable species establishment in response to microhabitat indicates different likelihoods of climate-driven range shifts

“…It is, however, now widely accepted that microclimate differs from macroclimate due to factors such as forest canopy cover (De Frenne et al, 2019;Haesen et al, 2021) and topography (Lawson et al, 2014). This can modify species response to habitat use (Lawson et al, 2014) and create climate change refugia (Dobrowski, 2011;Pradhan et al, 2023) that mediate species response to climate change (Morelli et al, 2020). Very few studies have been able to document how variable plant-relevant environmental drivers of performance are across macroscale gradients, although substantial progress is underway in including microclimate as part of biogeographical research (Kemppinen et al, 2023).…”