Conservation values in set-aside black alder forests adjacent to managed stands: short-term changes

Forests dominated by black alder (Alnus glutinosa) potentially support habitats with high biological diversity, including rare and endangered species with specific demands for the habitat. However, the knowledge on the response of set-aside black alder forests to adjacent stand management is still insufficient for planning sustainable forest management and requires additional studies on the dynamics of complex organism groups. We conducted repeated inventories of ground vegetation, epiphytic lichens, polypores, and mollusks in the periphery and interior of 10 set-aside black alder-dominated forest stands in Latvia over seven years after adjacent forest management, to determine the response of these organism groups. Our results showed that the diversity of the studied organism groups either remained unchanged or increased from 2004 to 2011. The volume of dead wood increased significantly in all studied plots and correlated positively with polypore abundance and species diversity. We observed an increase in mollusk species number in the stand interior, but not in the periphery plots. No significant spatial differences in forest stand parameters or species diversity were found between stand interior and periphery plots in either the first or the second survey. The obtained results suggested that the 60-meter periphery zone was able to maintain species richness and diversity similar to the interior, highlighting the importance of black alder-dominated forests in supporting species diversity across the studied organism groups.