XVI International Botanical Congess

Savannas are unusual in that they are dominated by two different life forms: grasses and trees. The existing model of grass-tree coexistence, which proposes that grasses and trees coexist through rooting niche separation, is not supported by recent empirical studies suggesting that another mechanism results in grass-tree coexistence. We use a demographic model to show that coexistence is possible for a wide range of conditions if interactions between grass biomass, fire intensity and tree recruitment are considered. The model's behaviour is consistent with the storage effect: a well described non-equilibrium mechanism of coexistence. Grass-tree coexistence is sensitive to tree resprouting ability, stem growth rates, seedling establishment and drought frequency.