Fire and herbivory shape belowground bud banks in a semi-arid African savanna

Abstract

Fire and herbivory are major drivers in tropical savanna ecosystems and they selected a flora composed of species able to cope with recurrent aboveground biomass removal. Renewal of the herbaceous stratum is made possible by resprouting, mostly through a belowground bud bank. Evaluating the impacts of disturbances on the bud bank can assist in predicting post-disturbance responses and system resilience. In a semi-arid savanna, we aimed to verify whether lower fire frequency, fire and herbivory exclusion could affect belowground bud bank and organs diversity and consequently, the resprouting potential. Lower fire frequency or suppression and absence of herbivory were expected to reduce the bud bank density, which was confirmed by our results. If the fire is suppressed or fire frequency is reduced, the total, graminoid and the shrub bud bank decreased, whereas herbivory exclusion resulted in total and a forb bud bank of lower densities. Belowground buds were identified in non-woody and woody rhizomes, stolons, root crowns, and bulbs or corms. Despite having bud banks of lower density, disturbance exclusion promoted belowground biomass accumulation. Our results indicated the importance of maintaining the endogenous disturbances to the preservation of the belowground community and regeneration strategy, guaranteeing resilience in semi-arid savanna communities.