Tree topkill, not mortality, governs the dynamics of savanna–forest boundaries under frequent fire in central Brazil

• DOI: 10.1890/08-0741.1
• Publication Date: 2009-05-18T17:28:43Z
• Authors: William A. Hoffmann; Ryan Adasme; M. Haridasan; Marina T. de Carv...; Erika L. Geiger; Mireia A. B. Pereira; Sybil G. Gotsch; Augusto C. Franco
• Keywords: Deforestation; Tropical savanna climate

Tropical savanna and forest are recognized to represent alternate stable states, primarily determined by feedbacks with fire. Vegetation-fire dynamics in each of these vegetation types largely the influence on fire behavior, as well effects behavior tree mortality, topkill (defined here complete death aerial biomass, regardless whether plant recovers resprouting), rate growth resprouts. We studied effect three savanna-forest boundaries central Brazil. Fire intensity was greater than forest, inferred a twofold height stem charring. Despite lower intensity, species exhibited higher rates topkill, which best explained their thinner bark, relative species. Following there no tendency for sprouts trees grow faster those species, contrary expectations, nor whole-plant mortality savanna. This contrasts observations high postburn many other tropical forests. The low transitional forests suggests that dynamic natural is fundamentally different from originating deforestation humid tropics. appear be much more resilient occasional incursion savanna, despite being unable invade frequently burned thin bark makes them particularly susceptible "fire trap," whereby repeated small prevents recruitment into adult size classes. Rapid will important escape trap, so we predict that, where frequent, should restricted high-resource sites. Here, Mg2+ Ca2+ concentrations had strong rates, suggesting elements may most strongly limit distribution fire-prone savannas.