Adapting to climate change: Applying climate change refugia to forest management and old-growth restoration

Background/Question/Methods

As climate change alters the distribution and abundance of organisms, recent studies have highlighted the potential of climate change refugia (CCR; areas relatively buffered from contemporary climate change) to support the persistence of biodiversity in regions that may otherwise become unsuitable with climate change. In addition to providing insight into biological processes, CCR can also be used by natural resource managers to develop climate resilient management strategies. Key challenges in implementing CCR in resource management lie in defining and detecting refugia, as well as understanding their relationship with biodiversity patterns and management strategies. Here we address this challenge in the temperate coastal forests of the Pacific Northwestern United States where declines in the extent of old-growth forests have heightened a need for effective strategies to restore this ecosystem, which provides valuable benefits including habitat for endangered species and carbon sequestration. We first used variation in remotely-sensed vegetation indices to identify and map CCR in an experimental forest and identified the relationships between biophysical variables and CCR presence using Boosted Regression Trees. We then assessed how CCR relate to vegetation characteristics in multivariate space using constrained ordinations. Finally, we examined the interaction between current restoration strategies (stand-thinning) and landscape buffering capacity.

Results/Conclusions

Our results suggest that incorporating CCR into forest management requires careful consideration of the interactions between CCR, biodiversity, and current management practices. Variation in vegetation indices were positively associated with recorded understory temperature, indicating that this method captures some aspects of landscape buffering capacity. Biophysical variables were strong predictors of CCR presence in our study area and topo-edaphic variables were relatively more important than climate-related variables. When examining the importance of CCR for forest biodiversity, CCRs significantly influenced species presence and relative abundance. We also found that stand-thinning, on average, reduces climatic buffering capacity. Our study examines a method of identifying CCR based on variation in vegetation responses to local climate and provides insight into one way of including climate change adaptation into on-the-ground management decisions.