Post-harvesting dynamics of the deadwood profile: the case of lowland beech-oak coppice-with-standards set-aside stands in France

Abstract

In most European temperate forests, the heavy harvesting of low-quality wood for energy, a low minimum harvest diameter and a short rotation period, result in the limited deadwood resources. However, areas are being set aside in managed forests to restore deadwood levels. Coppice-with-standards is a silvicultural method characterized by periodic logging which clear-cuts coppice trees and removes some standard trees. We studied the deadwood profile (i.e., both amount and diversity) in oak-beech coppice-with-standards over time-since-the-last-harvest in order to evaluate how long it takes to recover significantly high amounts and diversity of deadwood substrates. A total of 282 circular 500-m2 plots were set up in 24 forests in southwestern France. We sampled five time-since-harvest classes within 80 years of the time elapsed since the last harvest. At the plot level, we used Generalized Linear Mixed Models to compare both deadwood volume and diversity among time classes. Diversity was also compared within time classes through accumulation curves. Deadwood legacies were very scarce after harvesting, both for volume and diversity. It took more than 70 years for deadwood amounts to become significantly higher than just after harvest; deadwood diversity was significantly higher only 30–50 years after harvesting due to quick snag recruitment. Crown deadwood, a particularly specialized resource rarely recorded, provided roughly 10–20% of the total deadwood amount throughout the study period and should be systematically recorded in further studies. Time-since-the-last-harvest was the best explanatory variable for both deadwood volume and diversity. We therefore recommend installing permanent set-aside areas to ensure deadwood conservation.