Changes in carbon storage in fallow forests in the tropical lowlands of Borneo

The range of CO 2 emissions to the atmosphere from tropical land-use change has long been debated. A major source of uncertainty is attributable to the fluxes of CO 2 due to changes in tropical land use. For example, estimate is different depending on whether the biomass or carbon content of tropical forests is totally lost by burning or recovered by regrowth. To estimate CO 2 absorption by fallow forests after shifting cultivation, we investigated the floristic composition and measured the biomass of fallow forests in East Kalimantan, Indonesia. Above-ground biomass of fallow forests were 8–10 t/ha at one-year-old stands and 45–56 t/ha at 10–12-year-old stands, regardless of the floristic composition. It seems reasonable to suppose that 7.4% of carbon released to the atmosphere by tropical rain forest destruction is reabsorbed and stored by fallow forests in Indonesia. If this is a universal trend in other tropical forests, a significant amount of CO 2 is reabsorbed in fallow forests. We consider that fallow forests like the one studied here are substantial carbon sinks and help to offset the effects of anthropogenic CO 2 emissions.