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  1. Free, publicly-accessible full text available August 1, 2023
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  4. Abstract. The Greater Cape Floristic Region (GCFR) ofSouth Africa is a biodiversity hotspot of global significance, and itsarcheological record has substantially contributed to the understanding ofmodern human origins. For both reasons, the climate and vegetation historyof southwestern South Africa is of interest to numerous fields. Currentlyknown paleoenvironmental records cover the Holocene, the lastglacial–interglacial transition and parts of the last glaciation but do notencompass a full glacial–interglacial cycle. To obtain a continuousvegetation record of the last Pleistocene glacial–interglacial cycles, westudied pollen, spores and micro-charcoal of deep-sea sediments from IODPSite U1479 retrieved from SW of Cape Town. We compare our palynologicalresults of the Pleistocene with previously published results of Pliocenematerial from the same site. We find that the vegetation of the GCFR, inparticular fynbos and afrotemperate forest, responds to precessional forcingof climate. The micro-charcoal record confirms the importance of fires inthe fynbos vegetation. Ericaceae-rich and Asteraceae-rich types of fynboscould extend on the western part of the Paleo-Agulhas Plain (PAP), whichemerged during periods of low sea level of the Pleistocene.
    Free, publicly-accessible full text available January 1, 2023
  5. Fire activity varies substantially at global scales because of the influence of climate, but at broad spatiotemporal scales, the possible effects of herbivory on fire activity are unknown. Here, we used late Quaternary large-bodied herbivore extinctions as a global exclusion experiment to examine the responses of grassy ecosystem paleofire activity (through charcoal proxies) to continental differences in extinction severity. Grassy ecosystem fire activity increased in response to herbivore extinction, with larger increases on continents that suffered the largest losses of grazers; browser declines had no such effect. These shifts suggest that herbivory can have Earth system–scale effects on fire and that herbivore impacts should be explicitly considered when predicting changes in past and future global fire activity.
  6. 1. Herbivory is a key process structuring vegetation in savannas, especially in Africa where large mammal herbivore communities remain intact. Exclusion experiments consistently show that herbivores impact savanna vegetation, but effect size variation has resisted explanation, limiting our understanding of the past, present and future roles of herbivory in savanna ecosystems. 2. Synthesis of vegetation responses to herbivore exclusion shows that herbivory decreased grass abundance by 57.0% and tree abundance by 30.6% across African savannas. 3. The magnitude of herbivore exclusion effects scaled with herbivore abundance: more grazing herbivores resulted in larger grass responses and more browsing herbivores in larger tree responses. However, existing experiments are concentrated in semi-arid savannas (400–800-mm rainfall) and soils data are mostly lack- ing, which makes disentangling environmental constraints a challenge and priority for future research. 4. Observed herbivore impacts were ~2.1× larger than existing estimates modelled based on consumption. Wildlife metabolic rates may be higher than are usually used for estimating consumption, which offers one clear avenue for reconciling estimated herbivore consumption with observed herbivore impacts. Plant-soil feedbacks, plant community composition, and the phenological or demographic timing of herbivory may also influence vegetation productivity, thereby magnify- ing herbivore impacts. 5. Because herbivore abundance somore »closely predicts vegetation impact, changes in herbivore abundance through time are likely predictive of the past and future of their impacts. Grazer diversity in Africa has declined from its peak 1 million years ago and wild grazer abundance has declined historically, suggesting that grazing likely had larger impacts in the past than it does today. 6. Current wildlife impacts are dominated by small-bodied mixed feeders, which will likely continue into the future, but the magnitude of top-down control may also depend on changing climate, fire and atmospheric CO2. 7. Synthesis. Herbivore biomass determines the magnitude of their impacts on savanna vegetation, with effect sizes based on direct observation that outstrip existing modelled estimates across African savannas. Findings suggest substantial ecosystem impacts of herbivory and allow us to generate evidence-based hypotheses of the past and future impacts of herbivores on savanna vegetation.« less