International Journal of
Biodiversity and Conservation

  • Abbreviation: Int. J. Biodivers. Conserv.
  • Language: English
  • ISSN: 2141-243X
  • DOI: 10.5897/IJBC
  • Start Year: 2009
  • Published Articles: 624

Full Length Research Paper

Tree community structure and recruitment dynamics in savanna woodlands

Nina Bhola
  • Nina Bhola
  • Community and Conservation Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, P. O. Box 11103, 9700 CC, Groningen, The Netherlands.
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Joseph O. Ogutu
  • Joseph O. Ogutu
  • Biostatistics Unit, Institute for Crop Science, University of Hohenheim, Fruwirthstrasse 23, 70599, Stuttgart, Germany.
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Holly T. Dublin
  • Holly T. Dublin
  • IUCN ESARO, Wasaa Conservation Centre, P. O. Box 68200 Nairobi, Kenya.
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Fons Van der Plas
  • Fons Van der Plas
  • Community and Conservation Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, P. O. Box 11103, 9700 CC, Groningen, The Netherlands.
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Hans-Peter Piepho
  • Hans-Peter Piepho
  • Biostatistics Unit, Institute for Crop Science, University of Hohenheim, Fruwirthstrasse 23, 70599, Stuttgart, Germany.
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Han Olff
  • Han Olff
  • Community and Conservation Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, P. O. Box 11103, 9700 CC, Groningen, The Netherlands.
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  •  Received: 30 August 2019
  •  Published: 31 January 2020

Abstract

Climate, fire and herbivory rank among the key factors and processes shaping savanna woodland community composition and diversity.  We analyzed recruitment dynamics, community biomass, diversity, stability and composition and their relationships with rainfall fluctuations and herbivory in a savanna woodland community in the Masai Mara National Reserve of Kenya. Seedling and sapling recruitment varied differentially over time among the five commonest tree species. Rainfall exerted both positive and negative effects on recruitment dynamics, with saplings responding to longer rainfall lags than seedlings. The proportion of trees damaged by browsers peaked at intermediate rainfall levels and was higher for adults than seedlings or saplings. Community biomass, species richness and evenness increased with increasing rainfall. Biomass decreased, whereas richness and evenness hardly varied over time. Both rare and common species occurred in more diverse communities, prevalent at high rainfall locations, suggesting strong nestedness in community composition. Moreover, community stability and diversity appeared unrelated. Protection from browsers and lower per capita browsing pressure at high rainfall apparently enable rare species to successfully establish and elevate species diversity. If climate change makes droughts more frequent and intense and lowers soil moisture, browsing intensity could increase, reducing diversity and recruitment, especially of rare, stress-sensitive species.

 

Key words: Masai Mara, species diversity, habitat filtering, rainfall, browsing, fire, competition, stochastic processes, tree biomass.