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Data from: Context-dependent effects of shifting large herbivore assemblages on plant structure and diversity

Citation

Orr, Devyn et al. (2022), Data from: Context-dependent effects of shifting large herbivore assemblages on plant structure and diversity, Dryad, Dataset, https://doi.org/10.25349/D94W48

Abstract

Despite wide recognition of the importance of anthropogenically driven changes in large herbivore communities – including both declines in wildlife and increases in livestock – there remain large gaps in our knowledge about the impacts of these changes on plant communities, particularly when combined with concurrent changes in climate. Considering these prominent forms of global change in tandem enables us to better understand controls on savanna vegetation structure and diversity under real-world conditions.

We conducted a field experiment using complete and semi-permeable herbivore exclosures to explore the difference in plant communities among sites with wild herbivores only, with cattle in addition to wild herbivores, and with no large herbivores. To understand variation in effects across climatic contexts, the experiment was replicated at three locations along a topoclimate gradient in California. Critically, this is the first such experiment to compare cattle and wildlife impacts along an environmental gradient within a single controlled experiment.

Vegetation structure responded strongly to herbivore treatment regardless of climate. Relative to the isolated effects of wildlife, exclusion of all large herbivores generally increased structural components related to cover and aboveground biomass, while the addition of cattle led to reductions in vegetation cover, litter, shading, and standing biomass. Furthermore, wildlife had a consistent neutral or positive effect on plant diversity, while the effect of livestock addition was context-dependent. Cattle had a neutral to strongly negative effect at low aridity, but a strong positive effect at high aridity. These results suggest that 1) herbivore effects can override climate effects on vegetation structure, 2) cattle addition can drive different effects on diversity 3) herbivore effects on diversity are modulated by climate.

Synthesis. Our results illustrate very distinctive shifts in plant communities between two realistic forms of changes in ungulate herbivore assemblages—livestock addition and isolated large herbivore losses—particularly for plant diversity responses, and also that these responses vary across climatic contexts. This finding has important implications for the management and protection of plant biodiversity given that over a quarter of the Earth’s land area is managed for livestock and climate regimes are changing globally.

Methods

Methods are described in detail in Orr et al., Context-dependent effects of shifting large herbivore assemblages on plant structure and diversity.

Funding

National Science Foundation, Award: DEB-1900502