Data from: Savanna resilience to droughts increases with proportion of browsing wild herbivores and plant functional diversity

1. Maintaining the resilience and functionality of savannas is key to
sustaining the ecosystem services they provide. This maintenance is
largely dependent on the resilience of savannas to stressors, such as
prolonged droughts. The resilience to drought is largely determined by the
interaction of herbivores and the functional composition of vegetation. So
far, our understanding and ability to predict the response of savannas to
drought under different types of rangeland use and as a function of
vegetation composition are still limited. 2. In this study, we used the
ecohydrological, spatially-explicit savanna model EcoHyD to determine if
the resilience of a savanna rangeland towards prolonged droughts can be
enhanced by the choice of rangeland use type (grazer-dominated,
mixed-feeders or browser-dominated) and animal density. We evaluated the
ability of a Namibian savanna system to withstand droughts and to recover
from droughts based on its perennial grass cover and the overall species
composition. 3. Generally, we determined a low resilience under high
grazer densities. Most importantly, we found that functional
diversification of herbivores and plants acted as resilience insurance
against droughts, leading to greater resistance and recovery of perennial
grasses. In particular, a higher proportion of herbivores allowed for
higher resilience, probably also due to a short-term switch to more
drought-resistant or unpalatable species.  4. In this case,
herbivore diversification was of high self-regulatory value by
reestablishing trophic complexity, reducing the need for additional
management interventions.  5. Synthesis and applications. Savanna
systems will be more resistant to drought if (i) a dense perennial grass
cover is maintained, protecting the topsoil from heat-induced water losses
and erosion, encompassing functionally important species that are
particularly well adapted to water stress and that are palatable, if (ii)
the grazing pressure is adjusted to the productivity of the system, and
(iii) the herbivore community includes browsers.