Fire history in the serpentine‑soil Spanish firs of Sierra Bermeja

Abstract

Background Abies pinsapo Clemente ex Boiss. is a species classified as endangered and currently occupies a very small and fragmented area of distribution in the southwest of the Baetic System. The uniqueness of these relict forests has motivated their study from different perspectives: phytogeography, faunal and floristic communities or biotic and abiotic risks. However, the paleoecological characterisation of this fir is still clearly deficient. Consequently, there is hardly any information on the impact that fire has had on this conifer during the Holocene nor the real effect that this disturbance has had on the Spanish fir in recent decades. To fill this knowledge gap, the present research uses the pedoanthracological network developed over the last 10 years in Sierra Bermeja, one of the natural habitats of the Spanish fir forest most affected by fire. This discipline is based on the analysis of the charcoals present in the natural soils, which are an unexplored resource and particularly useful for the reconstruction of paleo-fires and the knowledge of the dynamics of the vegetation. This paleoecological approach has also been complemented by the mapping of recent forest fires. Both approaches constitute the methodological body of this study. Results The identification of Abies charcoal in places where this taxon is not present today supports the idea that the Spanish fir was more widely distributed in the past. Likewise, the available dates (between 9931−9616 and 294−102 years cal BP) have revealed the existence of up to 28 events of forest fires that have affected the Spanish fir during the Holocene. The recurrence of fire could have caused its local extinction in the Sierra Palmitera. This reduction of the distribution area of the Spanish fir as a consequence of fire, as can be inferred from the cartography carried out, has been particularly intense during the last few decades, with almost 4500 fir trees affected. Conclusions Results report on the important role played by fire in the dynamics of the serpentine-soil Spanish firs of Sierra Bermeja from the Last Glacial Maximum to the present day. This is a phenomenon that has intensified in recent decades, affecting the Spanish fir in a very worrying way. Consequently, we insist on the need to include the whole of Sierra Bermeja in the Spanish National Park Network to help ensure effective protection for the most important serpentine-tolerant ecosystem in Spain.