Partition Idéalisée et Régionalisée de la Composition en Espèces Ligneuses des Forêts Françaises

ABSTRACT Forest tree species strongly influence forest dynamics and management. French forests have the greatest compositional diversity in Europe, which constrains the quantitative analysis of associated wood resources. A partition of French forests according to dominant tree species composition and stratified by biogeographical regions (GRECO) was developed in order to handle this diversity. The partition relies on forest composition as measured by the national forest inventory (2006–2015, > 65,000 plots). It builds on the J-shaped distribution of elementary composition abundance, identifies dominant compositions describing at least 50% of the GRECO's area, and groups minor compositions. An ecological assessment of this partition and its application to the analysis of the growing stock are developed. The partition describes 61.4% of the forest area (66% of the growing stock) according to 29 dominant compositions, demonstrating its efficiency. These compositions revealed the importance of broadleaved mixtures, and of neglected forest strata (pine species in Northern France). Growing stock density appeared lowest in broadleaved compositions (Mediterranean oaks), and highest in some coniferous compositions (silver fir/ Norway spruce mixture in mountains). Partitioning highlights the role of ecological contexts and forest management on tree diversity.