Spatial and Temporal Variations in Aboveground Woody Carbon Storage for Cerrado Forests and Woodlands of Mato Grosso, Brazil

摘要

Tropical forests and savanna account for nearly 65% of the total global terrestrial net primary production (NPP); however, there are still large uncertainties in tropical forest NPP because of limited field measurements, especially in the structurally diverse Brazilian savanna (cerrado). To address this uncertainty, we measured patterns of aboveground wood C stocks (C_w) and rates of wood C storage (ΔC_w) over a 7-year period for cerrado forests and woodlands of southern Mato Grosso, Brazil, arrayed across hydrological and soil fertility gradients. We focused on ΔC_w because it is an important component of NPP, and wood is a stable, long-term, C storage reservoir. Annual rates of ΔC_w were significantly affected by estimates of P and cation (K and Ca) availability, and analysis of covariance indicated that relationships between ΔC_w and nutrient availability were independent of stand hydrology. Both upland and hyperseasonal stands exhibited a decline in ΔC_w during the 2015-16 El Ni?o event, which was exceptionally warm and dry. A limited analysis of the uncertainty associated with the field measurements ranged from 7% for wood density to 24% for tree density, while the uncertainty associated with derived quantities ranged from 10% for tree height to 41% for C_w. Overall, these results suggest that soil fertility and annual precipitation are important drivers of ΔC_w and that warming and drying associated with climate change will cause a decline in aboveground woody C storage for these, and similar, tropical forests and woodlands.