Assessing the recovery of Pinus canariensis stands after wildfires and volcanic eruption on La Palma, Canary Islands

Abstract

The exposure of insular species to local disturbances can influence their evolutionary trajectory resulting in specific adaptations. On the island La Palma, Canary Islands, the archipelago-endemic tree species Pinus canariensis forms forest ecosystems and has been described to be adapted to wildfires. The frequency of these in the recent past, however, is higher due to anthropogenic activities. Recent studies suggest that the species traits might also be an evolutionary response to volcanic outbreaks, consisting of massive sulfur dioxide (SO₂) emissions and ash fall. Several stands of P. canariensis have been exposed to both disturbances, wildfires and volcanic outbreaks, in the recent past. We assess the recovery of P. canariensis after double exposure to these disturbances. P. canariensis recovery was assessed based on Sentintel-2 NDVI images within a 7 km radius of the craters of the Tajogaite volcano that erupted in 2021. Within the same area, wildfires occurred in 2009, 2012 and 2016. We used a Generalized Additive Model (GAM) to assess the recovery of P. canariensis after volcanic and wildfire disturbances. The model shows the P. canariensis forest recovers after the volcanic outbreak with a peak at a distance of 1000–1200 m to the eruption crater, which is in line with our first hypothesis. Our second hypothesis was met with unexpected results, forests exposed to the recent wildfire in 2016 showed an increased recovery, which underlines that P. canariensis exhibits traits related to fire adaptation or might also be the result of stand-specific characteristics such as forest height or local topography. The double pressure of volcanic and forest fire disturbances did not lead to suppressed recovery of the Canary-endemic tree species and highlights the resilience of P. canariensis.