The root to shoot ratio of trees from open- and closed-canopy cerrado in south-eastern Brazil

Abstract

Background: The Brazilian savanna, or Cerrado, has been described as an ‘upside-down forest’, with higher below-ground than above-ground biomass. The cerrado vegetation, ranging from open grasslands to forests, comprises a wide range of ecological conditions and plant biomass. Aims: To determine if and how root:shoot ratio in 102 trees differed between open- (cerrado sensu stricto) and closed-canopy cerrado (cerradão) within the same region in south-eastern Brazil. Methods: Differences in root:shoot ratios and environmental conditions between the two cerrado types were examined, by uprooting and weighing trees from different species and functional groups. Results: Root:shoot ratio was higher in the open than in the closed cerrado, especially among deciduous species. Root:shoot ratio in the open cerrado was lower than reported for the same cerrado type in central Brazil. Soil fertility did not differ between cerrado types, but soil water was lower and light availability was higher in the open cerrado. Conclusions: The lower root:shoot ratio in closed than in open cerrado is probably a response to lower light and higher soil water availability, and/or to less frequent fires. Estimates of above-ground carbon storage alone significantly underestimate the carbon stock in open relative to closed cerrado.