How to preserve precious broadleaved species in young dense beech stands: results of a 15 year experiment

With 1.3 106 ha, beech (Fagus sylvatica) is the third most represented species in France (Sardin et al. 2007). Because of its natural acute vitality, one of the major difficulties in its silviculture lies in preserving secondary objective-species mixed in stands (Armand et al. 2001). Actually, although precious broadleaved species such as Wild cherry (Prunus avium)should naturally grow scattered in young natural beech stands set on rich soils, beech is often almost the only species in older regular stands, because of a lack of suitable silviculture to these mixed species. Indeed the qualification phase (height between 3 and 12 meters) seems to be the key phase for their preservation. This is certainly a challenge for biodiversity and resilience to global climate changes, which are particularly worrying for the future of the beech in France and West Europe (Badeau et al. 2004). But also for timber production, the forester tries to obtain, at the lowest cost, vigorous and quality stems able to grow fast as soon as the expansion phase starts (Bock et al. 2005). The objective of the present study was to determine the best treatment for stems of three precious broadleaved species, isolated in young regular beech stand. Four strategies were tested, going from no treatment to intensive targeted thinnings. Fifteen years later, the results show contrasted performances between species, useful for foresters to improve young mixed beech stand silviculture.