Data from: Forests pests and the carbon cycle

Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores Winter Moth (Operophtera brumata L.) and Mottled Umber (Eranis defoliaria L.). In infested forests, net fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared to uninfested oak forests, with 4333 kg C × ha-1 and 319 kg N × ha-1, respectively, during a pest outbreak over three years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared to the non-infested forests. In microcosm incubation experiment, treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide (CO2) and 10-fold higher fluxes of dissolved organic carbon (DOC) compared to treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity, and therefore may represent an important mechanism by which climate change can initiate a carbon cycle feedback.