Windthrow and salvage logging alter β-diversity of multiple species groups in a mountain spruce forest

Abstract

The response of biodiversity to natural and anthropogenic disturbances is a central topic in applied ecology. Climate change has altered forest disturbance regimes, resulting in global increases in stand-replacing disturbances, which are regularly followed by the removal of trees (salvage logging). Yet, the mid- to long-term effects of disturbances and salvage logging and the importance of species relative abundances on β-diversity remain unclear. We compared the β-diversity of 13 taxonomic groups in intact forest, unlogged windthrow, and salvage-logged windthrow plots 11 years after a windthrow. Hill numbers were used to quantify differences in between-treatment and within-treatment β-diversity for rare, common, and dominant species. We found that over a decade post-disturbance, both windthrow and salvage logging led to significant changes in between-treatment β-diversity of all 13 taxonomic groups. In addition, differences in between- and within-treatment β-diversity were more pronounced for rare species than for common and dominant ones. Windthrow led to the homogenization of communities of most saproxylic and half of the non-saproxylic studied groups. However, contrary to our expectation, salvage logging did not further increase community homogenization for any taxonomic group or Hill number. Moreover, salvage logging even reversed the community homogenization caused by the windthrow for saproxylic groups, leading to more heterogeneous communities. This effect was likely caused by the relatively high amount and diversity of deadwood found on the salvage-logged plots. Our study suggests that differences in within-treatment β-diversity between salvaged and unsalvaged windthrows tend to vanish over time, whereas differences between-treatments persisted, especially for saproxylic groups and rare species. This finding underlines the importance of preserving the characteristic communities in unsalvaged wind-disturbed forests in the mid- to long-term. Therefore, we recommend a management strategy that balances the amount of salvage-logged areas with that of set-aside areas.