Woody plant biomass and carbon exchange depend on elephant-fire interactions across a productivity gradient in African savanna

Elephants and fire are individually well-known disturbance agents within savanna ecosystems, but their interactive role in governing tree-cover dynamics and savanna–forest biome boundaries remains unresolved. Of central importance are the mechanisms by which elephants vs. fire affect tree biomass and cover, and how – over long time periods – both factors interact with rainfall and soils to govern tree biomass and carbon dynamics. Here, we evaluated the response of woody vegetation to 56 years of fire manipulation in South Africa's Kruger National Park, with three fire regimes (annual, triennial and unburned) replicated across a productivity gradient and subject to two periods of contrasting elephant abundances (generated by the cessation of culling in 1994). Higher fire frequencies had a negative effect on woody biomass in the low-elephant period, but this effect was weak to negligible in the high-elephant period as the difference among fire treatments diminished. Moreover, elephants ...