Establishment of Broad-leaved Thickets in Serengeti, Tanzania: The Influence of Fire, Browsers, Grass Competition, and Elephants

Background

In Tanzania, thickets are declining due to frequent fires yet when the fires are removed the thickets fail to regrow. As a fire-resistant tree, seedlings of E. divinorum are potentially an ideal species to restore these land covers. 

Goals & Methods

This study investigates the role of Euclea divinorum in the establishment of broad-leaved thickets in grasslands of Serengeti National Park of Tanzania.Observation and experiments were conducted in 6 hilltop thickets and 6 riparian forests, termed focal study patches. Seedling abundance was examined inside thickets and forests along a 50 x 150 m belt transect from the forest edge to center. For identified seedling species, the distance to and identity of the nearest canopy tree was recorded. The effect of elephants damage to tagged E. divinorum was monitored. Also measured the DBH of 200 canopy trees in each of the six hilltops and riparian focal patches: E. divinorum and D. abyssinica in hilltop thickets and E. divinorum, D. abyssinica, D. gerrardii, and E. capensis in riparian forests.

Conclusions & Takeaways

Seedlings of E. divinorum were found at low densities in grassland areas, while other species were absent. Within the thickets and forests, all 12-canopy tree species were present. Seedlings were more abundant in the thickets than the E. divinorum grassland. The results suggest that E. divinorum has attributes of a pioneer species that can facilitate the establishment of hilltop thickets and riparian forests in the Serengeti. It establishes into the grassland areas and when mature, other tree species can establish beneath it. Establishment of new thickets and forests in East Africa through E. divinorum may depend on reducing browsing, removing grass and fire.