Contributions from dendroecology to distinguish what role play biotic factors and droughts in the forest decline

Abstract

Sangüesa-Barreda, G., Camarero, J.J., Linares, J.C., Hernández, R., Oliva, J., Gazol, A., et al. 2015. Role of biotic factors and droughts in the forest decline: contributions from dendroecology. Ecosistemas 24(2): 15-23. Doi.: 10.7818/ECOS.2015.24-2.03.

Increasing mortality and decline of forests are affecting several tree species and biomes. These events of forest decline have been related to the interaction of several global change elements, like the increase in drought stress or a higher incidence of biotic stress factors. However, the roles played by biotic stressors have been scarcely explored as related to drought stress. In this paper we retrospectively characterize the effects of these organisms on radial growth of trees already stressed by drought using dendrochronology. The combined effect of mistletoe and droughts reduce tree growth in Scots pine and increase defoliation, being these effects more noticeable in the apex. The pine processionary moth induces growth losses in the affected stands of black pine, but they usually recover two years after the outbreak. We did not find a determinate role of root pathogens on silver fir dieback. Finally, dead Aleppo pine trees infested by bark beetles showed similar growth patterns than living pine trees. This study allows characterizing some of the complex and multiple effects of different biotic stressors on growth and vulnerability of forests subjected to the negative effects exerted by droughts.