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Spatial dynamics of termite mounds

Spatial dynamics of termite mounds. AB Davies 1 , SR Levick 2 , GP Asner 2 , MP Robertson 1 , BJ van Rensburg 1 & CL Parr 3 1 Centre for Invasion Biology, Department of Zoology and Entomology , University of Pretoria 2 Department of Global Ecology, Carnegie Institution, Stanford, USA

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Spatial dynamics of termite mounds

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  1. Spatial dynamics of termite mounds AB Davies1, SR Levick2, GP Asner2, MP Robertson1, BJ van Rensburg1 & CL Parr3 1Centre for Invasion Biology, Department of Zoology and Entomology, University of Pretoria 2Department of Global Ecology, Carnegie Institution, Stanford, USA 3Department of Ecology, University of Liverpool, UK SR Levick

  2. African savannas • Highly variable environments WC Oosthuizen

  3. African savannas • Highly variable environments • Spatial heterogeneity important • Ecological functioning • Biodiversity • Ecosystem resilience WC Oosthuizen

  4. Savanna heterogeneity • Induced by several factors • Fire • Climatic events (variable rainfall) • Herbivory

  5. Termite mounds • Create heterogeneity

  6. Termite mounds • Create heterogeneity • Alter soil properties

  7. Termite mounds • Nutrient hotspots • Support richer, more nutritious vegetation • Focal feeding sites

  8. Termite mounds • Understanding their spatial patterns • Densities • Spatial patterning

  9. Termite mounds • Understanding their spatial patterns • Densities • Spatial patterning • Enable better understanding of heterogeneity and savanna functioning

  10. Mapping mounds • Carnegie Airborne Observatory (CAO) • Remote sensing system designed to study the 3D structure and function of ecosystems • Integration of light detection and ranging (LiDAR) and hyperspectral imagery

  11. Mapping mounds

  12. Mapping mounds

  13. Mapping mounds • Map mound dynamics across space • Densities • Mound structure • Spatial patterning

  14. Mapping mounds • Map mound dynamics across space • Densities • Mound structure • Spatial patterning • Mapped mounds across an entire river catchment – the N’waswitshaka

  15. Results 5 km

  16. Ripley’s K function

  17. Ripley’s K function 60 m

  18. Mapping mounds

  19. Stream order effects

  20. Crest patterns 5 km

  21. Crest patterns Decreasing clay content

  22. What this means… • Mounds are on crests • Where matrix vegetation is of poor quality WC Oosthuizen

  23. What this means… • Mounds are on crests • Where matrix vegetation is of poor quality • Evenly spaced on these crests WC Oosthuizen

  24. What this means… • Spatial distribution • High densities of large colonies in nutrient rich (dry) savanna WC Oosthuizen

  25. What this means… • Spatial distribution • High densities of large colonies in nutrient rich (dry) savanna • Associated with high levels of woody cover WC Oosthuizen

  26. What this means… • Spatial distribution • High densities of large colonies in nutrient rich (dry) savanna • Associated with high levels of woody cover • Induce positive feedback loops • Maintaining nutrient rich savanna WC Oosthuizen

  27. Acknowledgements • DST/NRF Centre of Excellence for Invasion Biology • Carnegie Institution for Science • Andrew Mellon Foundation • South African National Parks

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