Quantifying the recovery of old-growth attributes in forest reserves: A first reference for France

Abstract

Over the past centuries in Western Europe, the long history of forest management has shaped both landscape- and local-scale forest structures. In France, a network of strict forest reserves was created in the 1950s to serve as a reference for nature conservation and forest dynamics. However, few studies to date have quantitatively compared the structural characteristics between managed stands and the reserves, where management has been (more or less recently) abandoned. In addition, the time needed for old-growth characteristics to restore themselves in strict forest reserves remains poorly known.We analysed the differences in stand characteristics between managed and unmanaged stands in 17 French forests (233 plots) located in both lowland and in mountainous regions. We quantitatively showed that overall basal area, very large trees and deadwood features were significantly higher in unmanaged forests, though this pattern was mainly found in the lowland forests while in mountainous regions, managed and unmanaged forests showed far fewer differences. In addition, most structural characteristics that were higher in unmanaged forests also increased with the time since last harvesting.Compared to the remaining old-growth forests elsewhere in Europe, the strict forest reserves in France often appear less mature, since they are still recovering from centuries of intensive management. Our results also show lower levels than those observed in other European studies on the restoration of old-growth characteristics over time; this indicates that it will take French reserves a very long time to reach values comparable to old-growth references in Europe. Our study constitutes one of the first references on unmanaged forests in France and may serve practitioners in their everyday management.