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Juvenile tree growth and demography in response to feral water buffalo in savannas of northern Australia: an experimental field study in Kakadu National Park

Werner, Patricia A., Cowie, I. and Cusack, John (2006). Juvenile tree growth and demography in response to feral water buffalo in savannas of northern Australia: an experimental field study in Kakadu National Park. Australian Journal of Botany,54(3):283-296.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 27 times in Scopus Article | Citations

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Title Juvenile tree growth and demography in response to feral water buffalo in savannas of northern Australia: an experimental field study in Kakadu National Park
Author Werner, Patricia A.
Cowie, I.
Cusack, John
Journal Name Australian Journal of Botany
Publication Date 2006
Volume Number 54
Issue Number 3
ISSN 0067-1924   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-33646705884
Start Page 283
End Page 296
Total Pages 14
Place of Publication Australia
Publisher CSIRO Publishing
Field of Research 0607 - Plant Biology
HERDC Category C1 - Journal Article (DEST)
Abstract Tree populations in the wooded savannas of northern Australia lack a well developed seed bank, but instead rely on a persistent ground layer of suppressed juvenile plants < 1m of indeterminate ages. The feral Asian water buffalo has been implicated as a factor in inhibiting the movement of juvenile trees to sapling stage. In a 6-year field study in Kakadu National Park, 656 juvenile plants were monitored for growth and survival, and in exploring the effects of buffalo, clipping surrounding vegetation and ambient. re. Buffalo were removed from one half of the sites across an environmental gradient in a landscape-scale experiment. Juvenile trees grew more slowly but fewer became dormant where buffalo were absent. Experimental clipping of surrounding vegetation produced significantly increased height at the buffalo-absent sites, but not at the buffalo-present sites, demonstrating that the positive effect of buffalo on growth was indirect, by reducing the competitive regime for juvenile trees. Within 3 years of removal of buffalo, ground-level green biomass increased 2-10 times and litter 1.3-2 times over a topographic gradient. Mortality of juvenile trees was not significantly different between buffalo-present and buffalo-absent sites when plots remained unburnt. By contrast, at buffalo-absent sites, three times more juveniles died after late dry-season. res than at unburnt sites, but there was no difference among buffalo-present sites. Overall, the total juvenile tree bank decreased by 7% where buffalo grazed and by 18% where buffalo had been removed. The study demonstrated a major mechanism(s) responsible for recorded changes in vegetation patterns of these savannas, whereby buffalo initiate a cascade of effects by changing ground-level biomass, which change competitive relationships and fuel loads, which then have an impact on tree growth and demography. The results are discussed with respect to dynamics of the juvenile tree bank and implications for long-term sustainability of these wooded savannas.
Keywords eucalyptus-tetrodonta
tropical savanna
terminalia-ferdinandiana
stomatal conductance
carbon assimilation
seasonal-changes
fire
saplings
munmarlary
territory
DOI http://dx.doi.org/10.1071/BT04135   (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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