Indicator species of broad-leaved oak forests in the eastern Iberian Peninsula

Abstract

The degraded state, scattered distribution and substrate type of Quercus pyrenaica forests in eastern Spain make them a subject of particular interest, as well as a priority for conservation efforts. An extension of Dufrêne and Legendre's indicator value (IndVal) analysis was applied to one hundred relevés. This extension of the IndVal method allowed us, by considering the preference of species for combinations of relevé groups, to obtain those species that represent local, but also regional, characteristics (as a new practical use). Our objective was to identify the species that best indicate the main ecological features of these broad-leaved oak forests. The usefulness of our analysis was evidenced at two levels: local indicator species, showing the characteristic species of individual sites and including the presence of endemics in the area; and indicator species of combinations of two or more sites, reflecting the affinities or relationships between these scattered forests.Most singular forests showed a higher number of local indicator species. The indicator species of each site combination represent the main ecological traits shared by these groups – such as proximity to the coast, land uses or postglacial migration pathways – thereby defining their relationships. Indicator value analysis with site group combinations (Multipatt function) proved to be a useful tool for the identification of different species that could serve both to determine the local forest conservation status and aid in its preservation, as well as contributing to an understanding of the life history of larger territories.