1. Large wild herbivores have substantial impact on vegetation composition, diversity and dynamics, particularly in African savannas comprising unique densities and diversity of wild ungulates. While many studies have explored the influence of ungulates and nutrients on herbs and grasses, relatively few have focused on woody plants. 2. Here we report a 10-year experiment in an open savanna to assess how excluding large ungulates influences the diversity patterns of woody plants on resource-rich Macrotermes termite mounds, and on the relatively resource-poor savanna matrix (i.e. off-mound). We recorded all woody plants in nine replicate sites each with four treatments comprising two resource-poor plots; unfenced and fenced off-mound (excluding large ungulates), and two resource-rich plots; unfenced and fenced on-mound plots. 3. We found that species richness and plot-level Shannon diversity were markedly greater on the resource-rich mounds than off-mound. Fencing resource-poor off-mound plots resulted in 75% mean increment in species richness, but richness in resource-rich on-mound plots was not affected by fencing. Similarly, we found no marked effect of fencing on plot-level diversity on-mound, but off-mound diversity had increased in 2015, from 0.68 ± 0.22 in unfenced off-mound plots to 1.28 ± 0.25 in fenced plots. Rarefaction curves, derived from the number of individuals per species per plot, indicate that these differences do not simply reflect changes in stem densities. Within-treatment beta-diversity was substantially higher off- than on-mound but ungulate exclusion was associated with little discernible changes on either habitat. 4. We conclude that ungulates reduce woody species diversity in resource-poor savanna areas but have little influence in resource-rich areas.