Long-term impact of an extreme wildfire and salvage logging legacies on ecosystem services provision: Decomposition and nutrient cycling in fire-prone Mediterranean pine forests

Abstract

New wildfire regimes under accelerated global change may have unprecedented effects on ecosystem services (ES) provision but may also be mediated by the biological legacies left onsite. However, until now, we know very little about these effects, especially over the long term after fire. We investigated the impact of an extreme wildfire event and the burned wood legacies resulting from a decade post-fire salvage logging of dead trees on the recovery of two regulating/supporting ES, i.e., litter decomposition and nutrient cycling, in fire-prone Mediterranean ecosystems dominated by Pinus pinaster forests. For this, we (i) performed a two-year decomposition experiment using the Tea Bag Index (TBI) as a standard method to determine the percentage loss of litter mass and decomposition rates over time, and (ii) quantified soil biochemical variables (microbial biomass C, and β-glucosidase, urease and acid phosphatase enzymatic activities) reflecting nutrient cycling processes, in the burned area and in an adjacent 40-year unburned forest (hereafter, control). Furthermore, we analyzed the influence of soil chemical properties, vegetation variables, and fine (FWD) and coarse (CWD) woody debris characteristics on the recovery of the ES supply capacity. Although our results revealed initial differences with lower litter mass loss in the burned compared to the control area, possibly due to the higher humidity conditions created by mosses and FWD in the unburned forest that favour decomposition processes, decomposition rates in the burned area approached those in the control area at the end of the experiment. Furthermore, nutrient cycling driven by plant and microbial enzymatic activities, recovered fully a decade after fire. However, contrary to our expectations, burned wood legacies did not influence the recovery of ES provision, possibly because CWD remains were mostly intact and not decayed.