Coarse woody debris requirements for maintaining land snail diversity in managed spruce forests

Coarse woody debris (CWD) plays a crucial role in maintaining biodiversity in forest ecosystems by supporting habitat complexity and influencing soil properties. This study investigates the effects of CWD on gastropod diversity within managed spruce (Picea abies) forests in the Czech Republic, comparing results to nearby nature reserves (NRs). Gastropod species richness and composition were evaluated at both plot (50 m × 50 m) and mesohabitat scales across gradients of CWD and beech (Fagus sylvatica) tree representation. Our results indicate significantly reduced species richness in managed forests (median 7 species per plot) compared to NRs (median 15 species), attributed to lower soil pH, calcium availability, and moisture due to the dominance of spruce and the limited availability of CWD. Species richness was positively influenced by CWD volume, with two amounts identified: a minimum of 4 ​m³·ha⁻¹ to prevent significant biodiversity loss and 20 ​m³·ha⁻¹ to support sensitive and dendrophile species. At the within-plot scale, CWD was the species richest mesohabitat, playing a particularly important role in acidic and nutrient-poor environments. Furthermore, beech basal area positively correlated with species richness, mitigating the negative impact of spruce. The findings highlight the critical need for changes in forest management, including increased retention of CWD and integration of deciduous trees, to support biodiversity in intensively managed forests. These measures are particularly urgent given the susceptibility of spruce monocultures to climate change and pest outbreaks. Gastropods, as sessile indicators of environmental change, may serve as effective umbrella species for conservation efforts targeting forest soil biodiversity.