Abstract
In African savannas, bottom-up soil nutritional factors and top-down herbivory have both been suggested to control the distribution patterns of bunch and lawn grasses. We tested the separate and combined roles of these factors on grassland distribution in a South African savanna by focusing on three main objectives, namely (1) are grazing patches and lawns restricted to specific soils or sites, (2) does herbivory alter rates of nutrient cycling which facilitates lawns and (3) are there any differences in foliage quality between lawn and bunch grass-dominated sites that might influence animals in choosing to feed on lawns? We set up ten sites along a grazing gradient in the Hluhluwe-iMfolozi Park in KwaZulu-Natal, South Africa. At these sites, we measured total soil nutrients, soil nutrient turnover rates and grass foliage nutrient concentrations. We found that in the Hluhluwe-iMfolozi Park the spatial distribution of lawn and bunch grassland types appears to be an animal-driven phenomenon and not dependent on specific soil properties. The short-structured and distinct species found in lawns do not appear to be restricted to nutrient-enriched patches. However, the grasses of these lawns had significantly higher nutrient concentrations, in their foliage, which might explain the high attraction to these patches by herbivores. We also did not find any animal-induced stimulation of nutrient cycling rates that are often associated with lawn grass species.
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Acknowledgements
This research was funded by the National Research Foundation of South Africa and the Andrew Mellon Foundation through the Zululand Grassland Project (ZLGP). We thank Dave Balfour and Sue van Rensburg and their research staff at the Hluhluwe-iMfolozi Park for their support and facilitation of the project. KZN Wildlife is acknowledged for allowing us to work in their reserve. We would also like to thank the staff of the ZLGP, Krissie Krook, Bernard Frauenknicht, Thobile Shelembe, Sinenhlanhla Mhlongo and their colleagues for assistance with sample collection. Thanks are also due to Tony Swemmer and Sally Archibald for their comments on the manuscript.
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Stock, W.D., Bond, W.J. & van de Vijver, C.A.D.M. Herbivore and nutrient control of lawn and bunch grass distributions in a southern African savanna. Plant Ecol 206, 15–27 (2010). https://doi.org/10.1007/s11258-009-9621-4
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DOI: https://doi.org/10.1007/s11258-009-9621-4