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A grass-fire cycle eliminates an obligate-seeding tree in a tropical savanna

Bowman, David M.J.S., MacDermott, Harry J., Nichols, Scott C. and Murphy, Brett (2014). A grass-fire cycle eliminates an obligate-seeding tree in a tropical savanna. Ecology and Evolution,4(21):4185-4194.

Document type: Journal Article
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ARC Grant No. LP110200006
IRMA ID 75039815xPUB881
Title A grass-fire cycle eliminates an obligate-seeding tree in a tropical savanna
Author Bowman, David M.J.S.
MacDermott, Harry J.
Nichols, Scott C.
Murphy, Brett
Journal Name Ecology and Evolution
Publication Date 2014
Volume Number 4
Issue Number 21
ISSN 2045-7758   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84927614187
Start Page 4185
End Page 4194
Total Pages 10
Place of Publication United Kingdom
Publisher John Wiley & Sons Ltd.
HERDC Category C1 - Journal Article (DIISR)
Abstract A grass–fire cycle in Australian tropical savannas has been postulated as driving the regional decline of the obligate-seeding conifer Callitris intratropica and other fire-sensitive components of the regional flora and fauna, due to proliferation of flammable native grasses. We tested the hypothesis that a high-biomass invasive savanna grass drives a positive feedback process where intense fires destroy fire-sensitive trees, and the reduction in canopy cover facilitates further invasion by grass. We undertook an observational and experimental study using, as a model system, a plantation of C. intratropica that has been invaded by an African grass, gamba (Andropogon gayanus) in the Northern Territory, Australia. We found that high grass biomass was associated with reduced canopy cover and restriction of foliage to the upper canopy of surviving stems, and mortality of adult trees was very high (>50%) even in areas with low fuel loads (1 t·ha−1). Experimental fires, with fuel loads >10 t·ha−1, typical of the grass-invasion front, caused significant mortality due to complete crown scorch. Lower fuel loads cause reduced canopy cover through defoliation of the lower canopy. These results help explain how increases in grass biomass are coupled with the decline of C. intratropica throughout northern Australia by causing a switch from litter and sparse perennial grass fuels, and hence low-intensity surface fires, to heavy annual grass fuel loads that sustain fires that burn into the midstorey. This study demonstrates that changes in fuel type can alter fire regimes with substantial knock-on effects on the biota.
Keywords Alternate stable states
Fire regime
Grass-fire cycle
Invasion ecology
Tropical savanna
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Additional Notes This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Description for Link Link to CC Attribution 4.0 License

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