Charles Darwin University

CDU eSpace
Institutional Repository

 
CDU Staff and Student only
 

Impact of feral water buffalo and fire on growth and survival of mature savanna trees: An experimental field study in Kakadu National Park, northern Australia

Werner, Patricia A. (2005). Impact of feral water buffalo and fire on growth and survival of mature savanna trees: An experimental field study in Kakadu National Park, northern Australia. Austral Ecology: a journal of ecology in the Southern Hemisphere,30(6):625-647.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 44 times in Scopus Article | Citations
Altmetric Score Altmetric Score is 3
Google Scholar Search Google Scholar

IRMA ID A00008xPUB10
Title Impact of feral water buffalo and fire on growth and survival of mature savanna trees: An experimental field study in Kakadu National Park, northern Australia
Author Werner, Patricia A.
Journal Name Austral Ecology: a journal of ecology in the Southern Hemisphere
Publication Date 2005
Volume Number 30
Issue Number 6
ISSN 1442-9985   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-23444451958
Start Page 625
End Page 647
Total Pages 23
Publisher Wiley-Blackwell Publishing Asia
Field of Research 0602 - Ecology
HERDC Category C1 - Journal Article (DEST)
Abstract The impact of feral Asian water buffalo (Bubalus bubalis) and season of fire on growth and survival of mature trees was monitored over 8 years in the eucalypt savannas of Kakadu National Park. Permanently marked plots were paired on either side of a 25-km-long buffalo-proof fence at three locations on an elevational gradient, from ridge-top to the edge of a floodplain; buffalo were removed from one side of the fence. All 750 trees >= 1.4 m height were permanently marked; survival and diameter of each tree was measured annually; 26 species were grouped into four eco-taxonomic groups. The buffalo experiment was maintained for 7 years; trees were monitored an additional year. Fires were excluded from all sites the first 3 years, allowed to occur opportunistically for 4 years and excluded for the final year. Fires were of two main types: low-intensity early dry season and high-intensity late dry season. Growth rates of trees were size-specific and positively related to diameters as exponential functions; trees grew slowest on the two ends of the gradient. Eucalypt mortality rates were 1.5 and 3 times lower than those of pantropics and of arborescent monocots, respectively, but the relative advantage was lost with fires or buffalo grazing. Without buffalo grazing, ground level biomass was 5-8 t ha(-1) compared with 2-3 t ha(-1), within 3 years. In buffalo-absent plots, trees grew significantly slower on the dry ridge and slope, and had higher mortality across the entire gradient, compared with trees in buffalo-present plots. At the floodplain margin, mortality of small palms was higher in buffalo-present sites, most likely due to associated heavy infestations of weeds. Low-intensity fires produced tree growth and mortality values similar to no-fire, in general, but, like buffalo, provided a 'fertilization' effect for Eucalyptus miniata and Eucalyptus tetrodonta, increasing growth in all size classes. High-intensity fires reduced growth and increased mortality of all functional groups, especially the smallest and largest (> 35 cm d.b.h.) trees. When buffalo and fires were excluded in the final year, there were no differences in growth or mortality between paired sites across the environmental gradient. After 8 years, the total numbers of trees in buffalo-absent plots were only 80% of the number in buffalo-present plots, due to relatively greater recruitment of new trees in buffalo-present plots; fire-sensitive pantropics were particularly disadvantaged. Since the removal of buffalo is disadvantageous, at least over the first years, to savanna tree growth and survival due to a rebound effect of the ground-level vegetation and subsequent changes in fire-vegetation interactions, process-orientated management aimed at reducing fuel loads and competitive pressure may be required in order to return the system to a previous state. The 'footprint' of 30 years of heavy grazing by buffalo has implications for the interpretation of previous studies on fire-vegetation dynamics and for current research on vegetation change in these savannas.
Keywords bubalus bubalis
eucalyptus population dynamics
fire
savanna
tree growth
eucalyptus-tetrodonta savanna
central arnhem-land
tropical eucalyptus
monsoonal australia
woody vegetation
seasonal-changes
gunn-point
management
forests
munmarlary
DOI http://dx.doi.org/10.1111/j.1442-9993.2005.01491.x   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
Versions
Version Filter Type
Access Statistics: 264 Abstract Views  -  Detailed Statistics
Created: Fri, 12 Sep 2008, 08:35:25 CST by Administrator