Seasonality, drivers, and isotopic composition of soil CO 2 fluxes from tropical forests of the Congo Basin

[摘要] Soil respiration is an important carbon flux and key process determining the net ecosystem production of terrestrial ecosystems. To address the lack of quantification and understanding of seasonality in soil respiration of tropical forests in the Congo Basin, soil CO 2 fluxes and potential controlling factors were measured annually in two dominant forest types (lowland and montane) of the Congo Basin over 2 years at varying temporal resolution. Soil CO 2 fluxes from the Congo Basin resulted in 3.45  ±  1.14 and 3.13  ±  1.22  µ mol CO 2  m −2  s −1 for lowland and montane forests, respectively. Soil CO 2 fluxes in montane forest soils showed a clear seasonality with decreasing flux rates during the dry season. Montane forest soil CO 2 fluxes were positively correlated with soil moisture, while CO 2 fluxes in the lowland forest were not. Smaller differences of δ 13 C values of leaf litter, soil organic carbon (SOC), and soil CO 2 indicated that SOC in lowland forests is more decomposed than in montane forests, suggesting that respiration is controlled by C availability rather than environmental factors. In general, C in montane forests was more enriched in 13 C throughout the whole cascade of carbon intake via photosynthesis, litterfall, SOC, and soil CO 2 compared to lowland forests, pointing to a more open system. Even though soil CO 2 fluxes are similarly high in lowland and montane forests of the Congo Basin, the drivers of them seem to be different, i.e., soil moisture for montane forest and C availability for lowland forest.

[学科分类] 大气科学