Grazing lawn and flammable-tussock grass communities are contrasting resource pools for mammalian grazers in terms of forage quantity and quality. Drought events fundamentally alter forage availability within these communities and therefore should alter herbivore use with repercussions for the recovery and functioning of ecosystems after drought. During and after an intense El Niño drought (2014–2017) in Kruger National Park, South Africa, we addressed two questions: (1) how does herbivore use of different grass types change during a drought and (2) how do these changes affect grass productivity post-drought? We monitored grazer use of three different grass communities (lawn, tussock and burned-tussock) at a landscape scale and measured primary productivity monthly during and post-drought. For the first drought year, grazer numbers were highest on grazing lawn communities. This pattern continued into the second dry growing season, until herbivores finally left the study area. Both lawns and tussock grasslands recovered rapidly after the first good rainfall (productivity > 150 g m−2 per month). However, grazers did not return to feed on the same patches they had frequented pre-drought resulting in grazing lawn grasses self-shading and senescing. Longer droughts have the potential to decouple grazers and grazing lawns with negative impacts on lawn productivity and persistence that could drive the loss of lawns in savanna landscapes and impact mesoherbivore populations. It is clear from our results that grazer effects need to be incorporated into drought frameworks to understand the consequences of droughts for grassland function.
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Data have been submitted to South African National Parks (SANParks) online data repository http://dataknp.sanparks.org/sanparks/metacat/judithk.111311.2/sanparks.
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We thank Khensani Mkhonto for collecting data in the field. We are grateful to SANParks and Working on Fire for their continued support, particularly Navashni Govender and Tercia Strydom. This work was funded by the USAID/NAS program “Partnerships for Enhanced Engagement in Research” (Sub-Grant 2000004946, Cycle 3) and the Andrew Mellon Foundation. JED was funded by the National Research Foundation Freestanding, Innovation and Scarce Skills Development Fund (Grant No. 94250).
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Donaldson, J.E., Parr, C.L., Mangena, E.H. et al. Droughts Decouple African Savanna Grazers from Their Preferred Forage with Consequences for Grassland Productivity. Ecosystems 23, 689–701 (2020). https://doi.org/10.1007/s10021-019-00438-x
- African savannas
- fire ecology
- grazer ecology
- grazing lawns