Contrasting responses of above- and below-ground carbon stocks and arthropods in relation to forest management

Forest ecosystems play a key role in mitigating both climate change and biodiversity loss, as they store large amounts of carbon and provide habitat for a diverse flora and fauna. However, for temperate European forests, several studies suggest that there are not unequivocally unidirectional correlations between carbon storage (above- and below-ground) and the diversity of biota across taxa. Although the effects of forest management on carbon stocks and biodiversity are well understood, the impact on their interrelationship remains unclear. Furthermore, previous studies have primarily examined the aboveground strata, despite the substantial contribution of the soil to carbon stocks and biodiversity. In this study, we synthesised data on carbon stocks, forest management intensity, and arthropods from the above- and below-ground strata, collected at 150 forest plots representative of Central European forests. In line with previous studies, total and aboveground carbon stocks decreased, whereas belowground carbon stocks increased with increasing forest management intensity. Furthermore, the response of arthropods to increasing management intensity was mixed. While total and aboveground carbon stocks were positively associated with the biomass of belowground arthropods and aboveground myceto-detritivorous insects, relationships between aboveground carbon stocks and aboveground arthropods were mainly positive, albeit negatively affected by increasing forest management intensity. Belowground carbon stocks were negatively associated with increases in belowground arthropods, but higher management intensity positively influenced these correlations. Our findings reveal that adjusting forest management to promote individual arthropod groups and carbon stocks can lead to trade-offs for other arthropod groups and for carbon stocks. Nevertheless, the observed trade-offs between different arthropod groups and carbon stocks suggest that promoting a mosaic of management types while reducing general management intensity might enhance habitat suitability for arthropods and the carbon storage potential. This could help to maximise synergies between storing large amounts of carbon and mitigating biodiversity loss in forests.