Document: WHE-3-59-40

Rates of aboveground biomass gain, and soil carbon accumulation and loss 60 years following tropical reforestation.

SILVER, W.L.* ¹, A.E.LUGO ², L.M.KUEPPERS ¹ and V.MATZEK ¹

University of California, Berkeley, CA 94720, USA ¹
International Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, PR, USA ²

Abstract:
High rates of tropical deforestation have prompted growing concern about the loss of C storage capacity, and increasing rates of C emissions to the atmosphere. Considerable recent efforts have focused on documenting the effects of deforestation and land use change on plant and soil C pools. Much less research has explored possible mechanisms to help offset C losses through reforestation. In this study, we use ¹³ C analyses and forest inventories to quantify rates of soil and plant C accumulation in a subtropical moist forest 60 years following restoration of forest from pasture. We also measured the effects of species richness, composition, and basal area density on rates of C accumulation, litterfall and fine root production in the restored ecosystem. Species richness had increased to 75 in 1991 from the original 13 species that were planted. Total aboveground biomass was 158 Mg/ha, and accumulated at a rate of 2.92 ( 0.10) Mg/ha/yr. Most tree species, including early successional species, grew faster during the second 32 years of growth than in the first 22 years. There was no affect of species richness on above- or belowground productivity. Native species had the highest importance values, and accumulated aboveground C at the fastest rates. Three non-native timber species were among the 10 species with the greatest aboveground biomass for the forest. Litterfall net primary productivity (NPP) was 12.9 0.7 Mg/ha/yr, and fine root productivity was 0.2 Mg/ha/yr. Litterfall NPP was high relative to other tropical moist forests. Belowground C pools were greater in the forest (99.5 1.6) than in adjacent pasture of similar age (68.8 9.0). Forest soil C accumulated at rate of approximately 1 Mg C/ha/yr, but residual pasture C was lost at a rate 0.3 Mg C/ha/yr, yielding a net gain of 37 Mg C/ha in the forest soil over the 60 year period. Our results suggest that restored tropical moist forests can be an important sink for both above- and belowground C. The choice of species used for reforestation is likely to affect rates and patterns of C sequestration through species-specific traits that influence C allocation patterns, litter quality, or alteration of microclimate and edaphic conditions.

Keywords: Carbon Sequestration, Soil Carbon, Aboveground Biomass, Tropical Forests, Reforestation

This abstract is being presented at: 2:45 PM in session:
Oral Session #52: Carbon Storage in Ecosystems.