Termites confer resistance to changes in tree composition following reduced browsing in an African savanna

QUESTIONS: Ungulates affect plant community structure and composition. Vegetation response to these effects are variable. Wild large herbivore populations are declining globally, but how tree communities respond to this change is not clear. We experimentally examined how tree communities respond to changes in ungulate abundance in a heterogeneous landscape. LOCATION: Lake Mburo National Park, Uganda. METHODS: We recorded tree species in nine replicate sites each with four treatment plots: fenced off‐mound (excluding ungulates), unfenced off‐mound, fenced and unfenced on‐mound. Each species was assessed for fruit type, leafing strategy, spinescence and bark thickness. We compared tree communities on‐ and off‐mound, with and without ungulates using PERMANOVA, and the effects of habitat, fencing and time on stem density and traits using generalized linear mixed effects model. RESULTS: Stem density increased by 88% off‐mound and 138% on‐mound (p = 0.005) with fencing, between 2006 and 2015. Whether tree communities occurred on‐ or off‐mound determined species composition, but fencing had little effect. Tree traits were not markedly altered by fencing on‐mound. Off‐mound, fencing was associated with a 38% increase in the proportion of fleshy‐fruited tree stems (p < 0.001), 18% decline in armed tree stems (p = 0.035) and a 44% reduction in mean bark thickness (p = 0.001). CONCLUSION: Our study highlights the important role mounds play in maintaining tree community composition with declining ungulate abundance. While ungulates influence tree communities off‐mounds they have little effect on tree composition and traits of mound‐borne trees. Thus, Macrotermes mounds support distinct tree communities that are robust to exclusion of ungulates.