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Strong competitive effects of African savanna C4 grasses on tree seedlings do not support rooting differentiation

Published online by Cambridge University Press:  31 January 2018

Benjamin L. Ketter  and
Ricardo M. Holdo
Benjamin L. Ketter
Affiliation:
Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA
Ricardo M. Holdo*
Affiliation:
Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
*
*Corresponding author. Email: rholdo@uga.edu
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Abstract:

Rooting differentiation between established trees and grasses has been well documented in savannas, but it remains unclear to what extent tree-grass rooting differences affect competition between newly established seedlings and grasses. To examine this question, a greenhouse experiment was conducted at the University of Missouri, USA. Twenty 3-mo-old seedlings each of two African savanna tree species (Acacia nigrescens and Colophospermum mopane) were grown for 8 mo with two crossed factors: grass competition and irrigation depth. Strong negative effects of grass competition on final seedling biomass and leaf photosynthetic and stomatal conductance occurred in both tree species, but no effects of irrigation depth were detected. There was a clear tree species by grass competition interaction, suggesting interspecific variation in competitive response. The results emphasize the importance of below-ground competition with grasses for physiological and morphological responses of tree seedlings, while minimizing the importance of tree-grass rooting depth differences as a factor in modulating the competitive response of trees to grasses at the seedling stage.

Keywords

Africasoil moisturestomatal conductancetree growthtree-grass competitiontropical savanna
Type
Research Article
Information
Journal of Tropical Ecology , Volume 34 , Issue 1 , January 2018 , pp. 65 - 73
Copyright
Copyright © Cambridge University Press 2018 

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