Evaluating habitat structural variables as reliable indicators of biodiversity in Mediterranean forests

Laurent Larrieu vient de publier un nouvel article en collaboration avec des collègues de Catalogne Espagnole dans la revue Forest Ecology and Management sur l'évaluation de variables structurelles d’habitat en tant qu'indicateurs robustes de la biodiversité dans les forêts méditerranéennes. Cette étude visait à compléter la calibration pluritaxonomique de l’indice de biodiversité potentielle (IBP) dans le contexte méditerranéen (calibration des facteurs). les auteurs se sont focalisés sur les peuplements dominés par le Pin d’Alep, le Chêne pubescent et le Chêne vert. Les 6 taxa employés pour cette calibration couvrent une large gamme d’exigences écologiques : champignons et coléoptères saproxyliques, oiseaux, chauves-souris, plantes vasculaires et bryophytes épiphytes. Pour les 4 derniers taxa, ils ont constitué des sous-groupes « forestiers ». Les principaux résultats de l'article sont:

• chaque facteur composant l’IBP est lié à au moins un groupe ou sous-groupe taxonomique. Dans le détail, la densité des gros bois morts au sol, l'abondance de dendromicrohabitats, l'ancienneté de l’état boisé et la présence de milieux rocheux sont les facteurs qui présentent le plus grand nombre d'associations;

• les sous-groupes forestiers d'oiseaux, de plantes vasculaires et de bryophytes épiphytes sont davantage liés aux facteurs de l’IBP que les groupes complets correspondants, tandis que les chauves-souris forestières présentent une association similaire ; ces relations diffèrent selon que l'on se regarde la richesse ou l'abondance des espèces.

Rota, M., Piqué, M., Sazatornil, V., Feldman, M. J., Baiges, T., Guixé, D., Larrieu, L., Mundet, R., Pallarés, M., Vayreda, J. & Camprodon, J. (2025). Evaluating habitat structural variables as reliable indicators of biodiversity in Mediterranean forests. Forest Ecology and Management 587: https://doi.org/10.1016/j.foreco.2025.122727.

Abstract:

Sustainable forest management aims to integrate biodiversity conservation while maintaining economic and social functions. However, direct biodiversity monitoring is usually costly and time-consuming, making structural indicators a valuable tool for integrating conservation criteria into forest management. We used the ten habitat structural variables derived from the Index of Biodiversity Potential (IBP), a widely used tool for assessing potential forest biodiversity at the stand scale. This study aims to evaluate the effectiveness of these habitat structural variables as proxy indicators of biodiversity by analysing the relationships between IBP factors and various taxonomic groups, subgroups and ecological guilds in Mediterranean forests. We conducted IBP inventories in 85 plots across 22 stands of different Mediterranean forest types, where we also collected data of six taxonomic groups, four of which were subdivided into forest specialist subgroups. Generalized linear models were employed to test the relationships between habitat structural variables and the richness and abundance of taxonomic groups and subgroups. We found that each habitat structural variable was related with at least one taxonomic group or subgroup. Specifically, the density of logs, the abundance of Tree-related Microhabitats (TreMs), ancientness and the presence of rocky macrohabitats were the habitat structural attributes with most associations. Taxonomic groups showed different responses, ranging from one structural variable (for birds, saproxylic fungi, and bryophytes) and up to four (for forest birds). Forest subgroups of birds, vascular plants and epiphytic bryophytes were more related to structural variables than their corresponding full groups, while forest bats displayed similar associations. However, these relationships differed when focusing on species richness or abundance approaches. Saproxylic ecological guilds, particularly Phloeophagous/ cambiumophagous guild, demonstrated more significant relationships with habitat structural variables than the broader saproxylic beetle assemblage. Our findings highlight that all habitat structural variables contained in the IBP are relevant for biodiversity, but none can be used alone as proxy indicator of forest biodiversity. Therefore, to encompass a wider spectrum of taxa, it is widely recommended to use multiple variables for integrating biodiversity conservation criteria into management planning of the Mediterranean forests.