Biotic and abiotic effects determining the resilience of conifer mountain forests: The case study of the endangered Spanish fir

Abstract

Variations in temperature and rainfall patterns due to climate change will lead to alterations in the potential habitat of species. This change will affect the interactions between species, being more evident in vulnerable species with fragmented habitat. This study aims to test the importance of abiotic and biotic factors determining the niche of threatened species in mountainous conifer forests. We used as study case the endangered Abies pinsapo in Southern Spain to understand its co-occurrence patterns in relation to the distribution and habitat suitability of key competing species. We estimated the intensity of interactions in relation to environmental gradients and development stage by single and joint species distribution models using a Bayesian approach in combination with niche overlap metric methods. Average temperature of the coldest month and precipitation were key variables shaping the current distribution of A. pinsapo. The ensemble potential distribution of the species showed very high overlap with the distribution of A. pinsapo. The joint species distribution model showed a potential negative interaction between A. pinsapo and the adults of Q. faginea and P. halepensis and positively with Juniperus species. A. pinsapo populations located at the low elevation distribution area are the most vulnerable, ultimately triggering a shift towards higher altitudes in a context of climate change. This abiotic stress will be exacerbated by competition dynamics of competing species from lower altitudes. This likely shift is shared by other mountain conifer species, with a success in survival limited by the availability of suitable area at higher altitudes.