Mammalian herbivores, drought and invertebrate ecosystem engineers are among the main drivers of vegetation dynamics in grasslands and savannas. Although their individual effects are relatively well understood, and some studies have probed their pairwise interactions, it is unclear how all three might combine in real-world conditions. Writing in Journal of Ecology, Wells et al. address this gap using two complementary experiments from a savanna in Kenya. They analysed 15 years of vegetation data from an extensive large-herbivore exclusion experiment and 2 years of data from a smaller experiment with factorial combinations of herbivore exclusion, watering and fertilization to simulate nutrient enrichment near termite mounds. Despite some discrepancies, both experiments show that herbivory is the strongest driver of understorey plant dynamics (cover, species richness and community composition) in this savanna, but also that there are non-additive interactive effects of drought and proximity to termite mounds. Notably, some of these interactions are counter to the authors’ predictions. For instance, whereas earlier findings suggested that termite mounds act as refugia for savanna plants under water limitation, here termite mounds provide hotspots of plant cover only during non-drought years and without herbivores, and more broadly their effects are largely offset by drought and herbivores. The findings by Wells et al. illustrate the importance of investigating the interplay of climate and multitrophic interactions in drylands.
Original reference: J. Ecol. https://doi.org/10.1111/1365-2745.70036 (2025)
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