Browsing by Author "Stevens, Nicola"

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Dataset from : Browsing is a strong filter for savanna tree seedlings in their first growing season
(ARCHIBALD ECOLOGY LAB, 2021-06-15) Archibald, Sally; Twine, Wayne; Mthabini, Craddock; Stevens, Nicola
1: Newly germinated seedlings are vulnerable to biomass removal but usually have at least six months to grow before they are exposed to dry-season fires, a major disturbance in savannas. In contrast, plants are exposed to browsers from the time they germinate, making browsing potentially a very powerful bottleneck for establishing seedlings. 2: Here we assess the resilience of seedlings of 10 savanna tree species to top-kill during the first 6 months of growth. Newly-germinated seeds from four dominant African genera from across the rainfall gradient were planted in a common garden experiment at the Wits Rural Facility and clipped at 1 cm when they were ~2, 3, 4, and 5 months old. Survival, growth, and key plant traits were monitored for the following 2.5 years. 3: Seedlings from environments with high herbivory pressure survived top-kill at a younger age than those from low-herbivore environments, and more palatable genera had higher herbivore-tolerance. Most individuals that survived were able to recover lost biomass within 12 months, but the clipping treatment affected root mass fraction and branching patterns. 4: Synthesis: The impact of early browsing as a demographic bottleneck can be predicted by integrating information on the probability of being browsed and the probability of surviving a browse event. Establishment limitation through early-browsing is an under-recognised constraint on savanna tree species distributions. Data may be used without requesting permission after the J Ecology paper is published and in the public domain (estimated after October 2021).
Woody plant encroachment drives population declines in 20 of common open ecosystem bird species
(Wiley) White, Joseph; Stevens, Nicola; Fisher, Jolene; Reynolds, Chevonne