A satellite-based multi-dimensional approach to identify potential post-fire regime shifts in ecosystem functioning

Abstract

Wildfires can profoundly impact many aspects of matter flows and energy budgets in ecosystems. Exacerbated by projected shifts in climate, land use, and forest management, changes in fire regimes can lead to decreased ecosystem resilience, regime shifts, and ecosystem collapse. Thorough assessments of ecosystem resilience to wildfires are thus critical to bridge gaps between science, policy, and management. To that end, approaches based on ecosystem functioning offer an integrative view of ecosystem responses to wildfire-induced changes and provide quicker, quantifiable responses to disturbances that are more directly connected to ecosystem services. In that regard, satellite remote sensing can be employed to easily and frequently monitor multiple dimensions of ecosystem functioning over large areas and across time, and to evaluate ecosystem functioning resilience to wildfires. This study describes an approach for identifying potential regime shifts based on satellite-based surrogates of four key dimensions of ecosystem functioning: primary production, water content, albedo, and sensible heat. To that end, we classified the trajectories after wildfires in 2005, in NW Iberian Peninsula, for the 2000–2018 period, into five main types, using two metrics of medium-to-long term post-fire recovery. Then, we derived a synthetic indicator to analyse the overall “strength-of-evidence” of potential regime shifts across dimensions. Potential regime shifts were identified for each dimension of ecosystem functioning considered, with the main effects associated with the sudden removal of vegetation. For primary production, regime shifts may be linked to changes in land cover and use, as well as management. Changes in the concentrations of impervious and radiation-absorbing materials following wildfires may be responsible for regime shifts in water content and albedo, with loss of canopy moisture due to fire-related damage leading to vegetation mortality during post-fire recovery. On the other hand, regime shifts in sensible heat were less frequent, since wildfires tend to have transient effects on this dimension of ecosystem functioning. Overall, our results show that our approach successfully captured different patterns of post-fire recovery and resilience across multiple dimensions of ecosystem functioning. We argue that our approach can provide an enhanced characterization of ecosystem resilience to wildfires, and support the identification of potential regime shifts after such disturbances, ultimately upholding promising implications for post-fire ecosystem management.