Tree species diversity and abundance as indicators of understory diversity in French mountain forests: Variations of the relationship in geographical and ecological space

La diversité et l'abondance des essences d'arbres comme indicateurs de la diversité végétale du sous étage dans les forêts de montagne françaises: variations des relations dans l'espace écologique et géographique

C. Zilliox (1) , Frédéric Gosselin (1)

1 UR EFNO - Ecosystèmes forestiers

Trees are one of the main components of forest ecosystems; they modify resource levels (light, nutrients, water) that affect understory vegetation composition and diversity. Tree species diversity is used as a biodiversity indicator in various European and French monitoring schemes for sustainable forest management. Moreover, tree species basal area has been found to better indicate floristic biodiversity than tree species richness or diversity. Herein we empirically check this finding by analyzing data from mountain spruce-fir forests in France with Bayesian statistical models. We insist on the magnitude of the relationship and its variation in geographical and ecological space. Our results indicate that both tree species abundance (based on cover or basal area) and tree species richness and dominance are good indicators of some parts of understory vascular plant species richness. The effect of dendrometric indicators on floristic biodiversity varied among ecological groups and along ecological gradients such as aspect, soil acidity, region and altitude. As a result, plots with north-facing and south-facing slopes exhibited opposite relationships of species richness with tree species abundance, and so did plots located on acidic and basic sites. We discuss these results in light of other empirical results relating positive interactions between species and abiotic stress. Our study supports evaluating biodiversity indicators to determine when they actually have non-negligible relationships with biodiversity, i.e. for which ecological groups and in which ecological contexts.

Mots clés: ESSENCE FORESTIERE; SOUS ETAGE FORESTIER; ABONDANCE D'ESPECE; ARBRE FORESTIER; FORET DE MONTAGNE; RICHESSE SPECIFIQUE; DIVERSITE FLORISTIQUE; FLORE VASCULAIRE; ORIENTATION GEOGRAPHIQUE; FACTEUR ECOLOGIQUE; INDICATEUR DE BIODIVERSITE; BIODIVERSITE

Domaines: Sciences de l'environnement

C. Zilliox, Frédéric Gosselin. Tree species diversity and abundance as indicators of understory diversity in French mountain forests: Variations of the relationship in geographical and ecological space. Forest Ecology and Management, 2014, 321, pp.105-116. ⟨10.1016/j.foreco.2013.07.049⟩. ⟨hal-01094414⟩