Dynamics and drivers of aboveground biomass accumulation during recovery from selective harvesting in an uneven-aged forest

Selective harvesting is a common silvicultural practice to ensure sustainable use of uneven-aged forests, but our understanding of how multiple forest attributes interact to regulate aboveground biomass (AGB) dynamics following selective harvesting remains limited. Using repeated measurements of 13,996 stem-mapped trees distributed in a broad-leaved Korean pine forest (BKPF), we evaluated the recovery trajectory of AGB over a 7-year period following selective harvesting of different intensity: low (15.8% of basal area removed), medium (29.4%) and high (51.4%). In particular, we examined the effects of (1) tree species diversity, (2) stand structure and (3) the post-harvest density on the rate of AGB accumulation (the net annual increment). Despite the enhanced growth of residual trees by all harvesting treatments, rates of AGB accumulation declined with increasing harvesting intensity due to high mortality losses: mean mortality rates of high stands were more than double those of the unharvested stands. Small trees (DBH < 10 cm) suffered greatest mortality because of their sensitivity to changes in environmental conditions. Post-harvest stand biomass and basal area explained most of the variation in the rate of AGB accumulation, followed by stand structural attributes (quadratic mean diameter and growth dominance coefficient), while indices of species diversity (richness, Shannon diversity and evenness) were weak predictors. Our findings suggest that selective harvesting may promote forest production without loss of biodiversity and stimulate the growth of residual trees (particularly small-sized trees, as indicated by the reverse growth dominance) within BKPFs, but harvest intensities should not exceed ~ 30% basal area removed, because higher levels of harvesting are likely to cause serious delays in biomass recovery.