The Effects of Rainfall, Elephant and Fire on Woody Height Class Distributions in South African Savannas Georgette Lagendijk & Rob Slotow

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The effects of rainfall, elephant and fire on woody height class distributions in South African savannas Georgette Lagendijk & Rob Slotow Amarula Elephant Research Programme, University of KwaZulu-Natal Introduction Concern for the loss of trees within African savannas Are size classes missing from the savanna? Disruption of ‘natural’ tree size distribution, or population dynamics Three main ecological drivers: rainfall, fire and herbivory Introduction Fire-trap <3m Browsing trap, seedlings and saplings Fire and herbivory intrinsic to savannas BUT Active management Introduction Are disruptions in size distributions recruitment or mortality related? Study Area Kruger National Park Makalali Madikwe Mkuze Pilanesberg Pongola Phinda Rainfall: 450 – 764 mm Elephant: 0.13 – 0.68 km2 Fire: 2.5 – 71.7 years Height classes Seedling: ≤ 0.5 m Sapling: 0.5-1.5 m Small tree: 1.5-3.0 m Medium tree: 3.0-5.0 m Large tree: ≥ 5.0 m Results ( & discussion) Positive Negative Rainfall seedlings large trees saplings Elephant - seedlings medium trees large trees Fire seedlings - (longer fire medium trees return interval) large trees Results Indicator species Prolonged fire period (+): Combretum apiculatum, Grewia monticola Rainfall (+): Acacia nilotica, Euclea natalensis Elephant (-): Peltophorum africanum No sign models for Pappea capensis or Ziziphus mucronata Results Kruger National Park Missing size classes: medium (3-5 m) large (≥ 5.0 m) trees Conclusion Disruptions in size classes appear mortality related: elephant and fire Affecting transition of individual trees through different size classes Whether this is detrimental to population dynamics and thus the persistance of (specific) species, requires urgent attention Thank you! Management of Kruger National Park, Madikwe, Pilanesberg, Makalali, Phinda, Mkuze and Pongola, Bruce Page, Craig Packer, Dave Druce, Matt Repton, Lisette Moolman, Tenjiwe Ndlovu, Sven Bourquin, Debbie Donkin, Dehn von Ahlenveld, Audrey Delsink, Navashni Govender, Pieter Nel, Simon Naylor, Dr. Heinz Kohrs, Heike Zitzer , and UKZN students Funding: Amarula Elephant Research Programme National Research Foundation University of KwaZulu-Natal [email protected] .

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