The impacts of logging on carbon stocks, tree diversity and forest recovery in Vietnam

Tropical forests are important carbon (C) sinks and biodiversity hotspots. Yet, forests are seriously threatened by anthropogenic disturbances including logging, which is the main driver of forest degradation in Southeast Asia. Here, I analyse the impacts of logging intensity on C stocks, tree diversity and forest recovery in seasonal evergreen broadleaf lowland forests in north-central Vietnam. I established, measured and after two years re-measured twenty-four plots that vary in historical logging intensity, nine years after logging. Logging intensity, estimated by combining Landsat analysis and participatory mapping, was the main factor explaining the variability in aboveground carbon (AGC). Heavily logged forests stored only half the amount of AGC in stems ≥10 cm diameter as lightly logged forests, mainly due to a reduction in large trees. AGC of small trees, dead wood and belowground C stored small fractions of total C stocks, while the topsoil of 0–30 cm depth stored roughly half of total C stocks. Tree diversity did not differ significantly with logging intensity. Some compositional differences were observed with logging intensity, although the challenge of sampling at the species level sufficiently complicates interpretation. Community wood density decreased with logging intensity and timber species only occurred in small numbers in our plots, especially in the heavily logged sites. Vital rates and associated AGC fluxes did not differ with logging intensity during the two-year period. The forests suffered from typhoon-induced tree mortality and damage, with ~40% of plots experiencing a net annual reduction in AGC. This study shows the critical importance of reducing logging intensities to maintain high forest C stocks and community wood density and to prevent the depletion of timber species. Recent storm impacts retard the post-logging AGC recovery of these forests.