Impact of species composition on fire-induced stand damage in Spanish forests

Mixed forests play a fundamental ecological role increasing biodiversity and providing ecosystem services; it has been suggested they have higher resilience and resistance against disturbances, particularly fire. Here, we compare tree mortality in post-fire mixed and pure stands in Spain, on 2,782 plots and 30,239 trees during the period 1986 to 2007. We show evidence that mixed stands can have higher post-fire mortality than pure stands, and specific mixtures of species with different fire-related strategies increase the stand's vulnerability to fire damage versus pure stands of either species, such is the case of Pinus halepensis — Pinus nigra mixtures. Mixtures of two species often had higher mortality than species growing in pure stands. Combinations of species with different fire-related strategies can both enhance or reduce forest resistance. The role and management of mixed forests should be reconsidered after these findings, in order to enhance forest resilience to fires.