Multi-stemmed trees in subtropical coastal dune forest: Survival strategy in response to chronic disturbance

Authors

  • Emmanuel F. Nzunda,

    1. Forest Biodiversity Research Unit, School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X0l, Scottsville 3209, South Africa
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  • Megan E. Griffiths,

    1. Forest Biodiversity Research Unit, School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X0l, Scottsville 3209, South Africa
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  • Michael J. Lawes

    Corresponding author
    1. Forest Biodiversity Research Unit, School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X0l, Scottsville 3209, South Africa
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  • Nomenclature: Coates Palgrave (2002).

Corresponding author; Fax +27 332605105; E-mail lawes@ukzn.ac.za

Abstract

Questions: Is multi-stemming a survival strategy in response to chronic disturbance? Is multi-stemming under phylogenetic control? What environmental factors are associated with multi-stemming? When do trees initiate growth of multiple stems? Do multi-stemmed trees have limited stature?

Location: Subtropical Indian Ocean coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park, northeastern South Africa.

Methods: Tree physiognomy and environmental conditions were sampled in 20 transects that were 300 m long and 5 m wide.

Results: 38.9 % of trees were multi-stemmed, with no correlation between multi-stemming and taxonomic grouping. The multi-stemming trait was most associated with stem decumb-ency and substrate erosion and multi-stemmed individuals were less common in protected dune slacks. Trees at Cape Vidal appear to facultatively produce multiple stems from an early stage. There was no trade-off between tree height and stem number.

Conclusions: Coastal winds and the unstable dune substrate are important environmental correlates of multi-stemming. Both short stature and the high incidence of multi-stemming are related to the tree-disturbance interaction. The taxonomically widespread phenotypic plasticity in this trait indicates the importance of multi-stemming to tree survival even under low levels of disturbance.

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