Assessing the impact of land-use change on soil organic carbon dynamics in Central Panama using physical soil fractionation and stable carbon isotopes
Luitgard
C
Schwendenmann, University of Wyoming, lschwen@uwyo.edu
(Presenting)
Elise
Pendall, University of Wyoming, pendall@uwyo.edu
Tropical ecosystems play an important role in the global carbon budget. About 44% of global soil organic carbon (SOC) is located in tropical areas. Forest clearing in tropical regions is estimated to contribute about 23% to human-induced CO2 emissions. We use stable C isotopes coupled with soil fractionation techniques to evaluate SOC dynamics following forest clearing in Central Panama. Soil samples were taken at 0-5, 5-10, 10-15, 15-20, 20-30, 30-40 and 40-50 cm depths from an undisturbed forest site and an adjacent clearing where the forest was cut approximately 80 years ago. Carbon concentration throughout both profiles is highest in the macro-aggregate fraction (0.250-2 mm). 13C values of the macro-aggregate fraction of the undisturbed forest ranged form -28.3‰ in the topsoil to -23.5‰ in the subsoil. Carbon in the topsoil of the clearing was more enriched in 13C (-20.6‰), reflecting the input of C4 vegetation with 13C values of -19.1‰. The macro-aggregate fraction at both sites showed comparatively high 13C values in the subsoil, suggesting that microbial fractionation enriched the older/deeper soil organic carbon. Particle-size and density fractionation will help elucidate this pattern. The values of 13C for soil organic carbon will be used to determine the soil carbon pool sizes and to calculate the turnover time of soil organic carbon in this moist humid ecosystem. These experiments will contribute to parameterization of carbon cycle models for tropical ecosystems.
Submetido por Luitgard Schwendenmann em 12-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)