Do conservation measures in forest work? A comparison of three area-based conservation tools for wood-living species in boreal forests

Abstract

Loss of natural forests and decline in forest biodiversity has led to several policy initiatives in recent years. Despite this, the importance of smaller set-asides vs forest reserves for conservation measures is poorly understood. We aimed to evaluate the importance of three different area-based conservation measures commonly used in north-European forests; retention patches, woodland key habitats and forest nature reserves. We did this for two contrasting ecological systems; fungi in late-decay spruce logs and beetles in early-decay aspen snags.Eight replicated sites for each of the three conservation measures were investigated in a total of four boreal forest landscapes in south-Norway. Fungi were surveyed on existent late-decay spruce logs in two landscapes, and beetles trapped on experimentally added aspen dead-wood units in three landscapes. Richness and species composition were analyzed separately for specialist and generalist species.We found larger differences in species composition between conservation measures for old-growth fungi specialists than generalists, although species richness patterns were less clear. The main contrast was found between nature reserves and retention patches. On the other hand, specialist beetles associated with early-decay aspen showed no difference between set-asides. The assemblage of aspen generalist beetles tended to be richest in the woodland key habitats and showed clear differences between the conservation measures. There was considerable variation in response to conservation measures between landscapes, related to quality of the set-asides.Species specialized to an ephemeral, early-decay system were able to utilize such substrates in all of the conservation measures, while the smaller and more modified set-asides could not cater for the specialists dependent on stable, late-decay systems. Species with broader habitat demands in general responded to all conservation measures. We conclude that retention patches, woodland key habitats and forest reserves fill complementary functions for wood-living species in boreal forest and should all be part of future forest conservation strategies.