Coppice-with-standards with an overmature coppice component enhance saproxylic beetle biodiversity: A case study in French deciduous forests

Until its replacement by high forest systems in the 19th centuries, coppicing had been practiced in the deciduous broad-leaved forests of Central Europe for many centuries, serving as a source of fuel wood, charcoal and tan-bark for the local populations. Nowadays, some coppice-with-standards (CWS) stands have been converted to high forest by singling (sprout thinning), but many others were simply abandoned, resulting in CWS stands with an overmature coppice component. Little knowledge exists on the biodiversity hosted by such abandoned CWS.In this study, we compared stand features and saproxylic beetle biodiversity in CWS stands with a mature (20-year-old) coppice component to those in stands with an overmature (60-year-old) coppice component. For our study area, we selected 29 plots in 12 oak-hornbeam forests in five regions in northern France.We show that extending rotation age increases the amount of woody debris and alters the deadwood profile. The older the trees and the stands, the more coarse woody debris was created; this includes debris resulting from natural disturbance events. We demonstrated that overmature CWS stands have a higher saproxylic beetle richness than mature CWS. Moreover, even though we found few red-listed beetle species, their number tended to increase in the overmature CWS stands. These results are in line with the observed shift in deadwood profile. Indeed, the increase in deadwood volume along the maturity gradient seems to positively affect saproxylic beetle diversity. Consequently, we conclude that conserving CWS stands with an overmature coppice component can be a useful tool in biodiversity restoration management, in addition to set aside areas.

► We studied the effects of overmature coppice on saproxylic beetle diversity. ► Overmature coppice stands have a higher saproxylic beetle richness. ► Few red-listed beetle species, but tends to increase in the overmature coppice. ► Results in line with the observe shift in deadwood profile. ► Conserving overmature coppice can be a useful tool in biodiversity restoration management.