Grazing lawns in the African landscape: A comparison between South African and Tanzanian systems

Background/Question/Methods

Grazing lawns are highly‐utilized grassland patches that represent key resource areas for large herbivores. Within these lawns exists the potential for complex interactions among herbivores, plants, fungi, and soils. It is essential that we understand the mechanisms that presently maintain lawns today so that we can better predict how they may respond to future impacts such as climate change. Our study asked the following three key questions: (1) how is lawn vegetation different from the surrounding matrix? (2) Are the differences between the lawn and matrix associated with below ground factors? (3) Are differences due to plant community turnover or intraspecific variation? Two parallel studies were conducted in Kruger National Park, South Africa and Serengeti National Park, Tanzania to compare key functional and structural characteristics between lawns and the surrounding matrix. Six sites (lawn and matrix pair) were sampled in early 2011. Modified Whittaker plots were used to quantify: (1) species-level and community-level plant nutritional and structural variables, (2) soil variables and (3) arbuscular mycorrhiza fungal (AMF) colonization rates.

Results/Conclusions

KNP lawns were characterized by higher community-level foliar nitrogen and leaf-to-stem ratios than matrix plants, but no differences in soil N, C, or P were found. Additionally, KNP lawns showed greater species-level foliar P. In contrast, high community-level foliar P and Na, along with greater species-level foliar N in lawns compared to matrix were found in SNP. Unlike KNP, SNP had higher organic C in lawn soils. Neither study found differences in AMF colonization rates. The two studies help highlight the variability between grazing systems. Broadly, both sites share greater foliar nutritional quality within the lawns. Specifically, they differ between species-level and community-level patterns. Edaphic nutrients failed to directly account for the greater foliar nutrient concentrations that are prevalent in grazing lawns. This work expands upon previous knowledge of the mechanistic drivers within grazing lawns and their community composition.