Impact of logging on aboveground biomass stocks in lowland rain forest, Papua New Guinea

Greenhouse-gas emissions resulting from logging are poorly quantified across the tropics. There is a need for robust measurement of rain forest biomass and the impacts of logging from which carbon losses can be reliably estimated at regional and global scales. We used a modified Bitterlich plotless technique to measure aboveground live biomass at six unlogged and six logged rain forest areas (coupes) across two ;3000-ha regions at the Makapa concession in lowland Papua New Guinea. ‘‘Reduced-impact logging’’ is practiced at Makapa. We found the mean unlogged aboveground biomass in the two regions to be 192.96 6 4.44 Mg/ha and 252.92 6 7.00 Mg/ha (mean 6 SE), which was reduced by logging to 146.92 6 4.58 Mg/ha and 158.84 6 4.16, respectively. Killed biomass was not a fixed proportion, but varied with unlogged biomass, with 24% killed in the lower-biomass region, and 37% in the higherbiomass region. Across the two regions logging resulted in a mean aboveground carbon loss of 35 6 2.8 Mg/ha. The plotless technique proved efficient at estimating mean aboveground biomass and logging damage. We conclude that substantial bias is likely to occur within biomass estimates derived from single unreplicated plots.