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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 Niño 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.Plain Language Summary Tropical forests and savannas are important reservoirs for global carbon (C) storage, but there are still uncertainties in how much C is stored in these ecosystems, especially for savanna. We measured the amount and rate of C stored in aboveground wood for forests and woodlands of the Brazilian savanna in the southern part of the Amazon Basin. Rates of wood C storage increased as nutrient availability increased, and C storage declined during drought years for both seasonally flooded and non-flooded forests and woodlands. These results have implications for how climate and land-use change alter wood C storage in these globally important ecosystems.