Guild-specific responses of forest Lepidoptera highlight conservation-oriented forest management - Implications from conifer-dominated forests

The loss of biodiversity in forest ecosystems has led to a discussion on conservation-oriented forest management, particularly in intensively managed coniferous forest of the northern hemisphere. Two conservation-oriented management strategies, namely advancement of multi-layered forests stands and benign neglect of naturally disturbed stands, are currently being promoted over conventional management strategies of single-layered stands and salvage logging after natural disturbances. However, the effect of these conservation-oriented strategies on nocturnal Lepidoptera has not yet been assessed, despite the high contribution of this order to biodiversity. Here we used full assemblage data of forest-dwelling micro-moths and macro-moths to compare species densities and relative abundance of moths of the larval feeding guilds in single-layered and multi-layered stands, and in naturally disturbed salvaged or unsalvaged stands. We demonstrate that forest moth assemblages are sensitive to conservation-oriented forest management strategies. The relative abundance of moths of the saproxylic and detritus-feeding larval guilds was higher in naturally disturbed unsalvaged stands and in multi-layered stands, whereas that of moths of the moss-feeding larval guild was lower in multi-layered stands. These results corroborate the benefit of a benign-neglect strategy in the management of naturally disturbed stands in conserving saproxylic and detritus-feeding moths and in using natural disturbance to guide the enhancement of stand complexity. Our results demonstrate both the power of functional approaches to reveal slight changes in species communities and the importance of including micro-moths (a frequently disregarded group) in studies aimed at developing management implications for forest managers.