Dead-wood addition promotes non-saproxylic epigeal arthropods but effects are mediated by canopy openness
Restoring dead-wood amounts in forests is an increasingly and successfully applied conservation measure to counteract negative effects of intensive logging on biodiversity of saproxylic taxa. By contrast, if and how dead-wood addition bene?ts the vast number of non-saproxylic forest taxa, and how this varies with contextual factors like canopy openness, remains poorly understood. To enhance dead-wood addition strategies, it is thus important to understand how dead wood affects entire forests communities, not just saproxylic taxa. To untangle effects of dead-wood addition and canopy openness on non-saproxylic epigeal arthropods, we exposed different amounts of logs and branches on 190 0.1-ha plots located in sunny or shady mixed montane forests and sampled epigeal arthropods over three years. Canopy openness was a major driver of species assemblage omposition and clearly mediated the effects of dead wood on epigeal beetles, spiders/harvestmen and springtails. Most species groups responded positively to the addition of dead wood. All groups decreased in number with increasing dis- tance to dead wood. Dead wood affected taxa of both lower and higher trophic levels directly and taxa of higher trophic levels bene?tted also indirectly owing to bottom-up effects. Our results indicate that increasing the amount of dead wood for conservation of saproxylic taxa bene?ts also non-saproxylic epigeal arthropods and thus, a larger number of forest species than commonly assumed. Because of the strong effects of canopy open- ness, similar to those found for saproxylic taxa, dead wood in both sunny and shady forest stands is needed.