Variations in wood production and C storage of tropical savanna trees along an edaphic gradient in Mato Grosso, Brazil

Brazilian savanna (cerrado) is composed of vegetation and soil types that are spatially variable. To understand how woody growth and carbon (C) storage vary as a function of soil physical and chemical properties we installed plastic, spring-loaded dendrometers on over 500 trees in nine cerrado stands that varied in physiognomy, soil physical and chemical properties, and hydrology and measured changes in trunk diameter over a period of one year. Rates of trunk C storage ranged between -0.20 MgC ha-1 y-1 for upland grass-dominated cerrado (campo sujo) to 1.36 MgC ha-1 y-1 for hyperseasonal (seasonally flooded) gallery forest (cerradão). Using ANCOVA to factor out potential differences in site hydrology (flooded vs. upland), which are known to affect tree growth, we found that rates of trunk growth and C storage were significantly related to total soil N, extractable Ca, Mg, Al, and cation exchange capacity (CEC), and soil texture (sand and clay content and bulk density). Linear correlation indicated that both trunk growth and C storage were positively related to N, Ca, Mg, Al, CEC, and clay content and negatively related to sand content and bulk density. These results suggest that tree growth and C storage in our cerrado stands are nutrient limited; however, links between growth and soil texture may also indicate the potential for water limitation during the dry season. These data suggest that variations in soil fertility are important controls on ecosystem C storage in Brazilian cerrado. These results are qualitatively similar to those reported for tropical forests across regional fertility gradients in the Amazon Basin, and have implications for the maintenance of cerrado ecosystem C storage.