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Density Effects of a Dominant Understory Herb Isoglossa woodii (Acanthaceae), on Tree Seedlings of a Subtropical Coastal Dune Forest

Tsvuura, Zivanai, Griffiths, Megan E. and Lawes, Michael J. (2011). Density Effects of a Dominant Understory Herb Isoglossa woodii (Acanthaceae), on Tree Seedlings of a Subtropical Coastal Dune Forest. Biotropica,44(2):163-170.

Document type: Journal Article

IRMA ID 82057923xPUB74
Title Density Effects of a Dominant Understory Herb Isoglossa woodii (Acanthaceae), on Tree Seedlings of a Subtropical Coastal Dune Forest
Author Tsvuura, Zivanai
Griffiths, Megan E.
Lawes, Michael J.
Journal Name Biotropica
Publication Date 2011
Volume Number 44
Issue Number 2
ISSN 0006-3606   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84857689215
Start Page 163
End Page 170
Total Pages 8
Place of Publication United States
Publisher Wiley-Blackwell Publishing, Inc.
HERDC Category C1 - Journal Article (DIISR)
Abstract Suppression of tree seedlings by the understory is an important ecological filter with implications for tree diversity and dynamics. In a greenhouse competition experiment, we used seedlings of four canopy species from coastal dune forest (Diospyros natalensis, Euclea racemosa, Sideroxylon inerme and Apodytes dimidiata) to examine the relative competitive effects of the dominant understory herb Isoglossa woodii on seedling performance. We manipulated I. woodii density, light and nutrient levels and measured growth responses. Total seedling biomass decreased with density of I. woodii. The magnitude of biomass suppression with competitor density was similar among tree species. Consequently there was no discernable hierarchy of competitive ranking among tree species. The relative growth rate of seedlings decreased at higher densities of I. woodii and increased at higher nutrient levels but was unaffected by variation in light conditions. Aboveground biomass decreased at higher densities of I. woodii and at higher light levels but increased at higher nutrient levels. Size asymmetric competition for light and nutrients may be the major driver of aboveground interactions between tree seedling and I. woodii. While tree species showed no hierarchy of competitive ability their seedlings exhibited equivalent responses to competition from an understory dominant, permitting species coexistence and the maintenance of species diversity. 
Keywords aboveground biomass
competitive response
light gradient
monocarpy
pairwise species interactions
relative interaction index
soil fertility
DOI http://dx.doi.org/10.1111/j.1744-7429.2011.00788.x   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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