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Humid tropical rain forest has expanded into eucalypt forest and savanna over the last 50 years


Tng, DYP and Murphy, BP and Weber, E and Sanders, G and Williamson, GJ and Kemp, J and Bowman, DMJS, Humid tropical rain forest has expanded into eucalypt forest and savanna over the last 50 years, Ecology and Evolution, 2, (1) pp. 34-45. ISSN 2045-7758 (2012) [Refereed Article]


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Licensed under Creative Commons Attribution-Non Commercial 3.0 Unported (CC BY-NC 3.0)

DOI: doi:10.1002/ece3.70


Tropical rain forest expansion and savanna woody vegetation thickening appear to be a global trend, but there remains uncertainty about whether there is a common set of global drivers. Using geographic information techniques, we analyzed aerial photography of five areas in the humid tropics of northeastern Queensland, Australia, taken in the 1950s and 2008, to determine if changes in rain forest extent match those reported for the Australian monsoon tropics using similar techniques. Mapping of the 1950s aerial photography showed that of the combined study area (64,430 ha), 63% was classified as eucalypt forests/woodland and 37% as rain forest. Our mapping revealed that although most boundaries remained stable, there was a net increase of 732 ha of the original rain forest area over the study period, and negligible conversion of rain forest to eucalypt forest/woodland. Statistical modeling, controlling for spatial autocorrelation, indicated distance from preexisting rain forest as the strongest determinant of rain forest expansion. Margin extension had a mean rate across the five sites of 0.6 m per decade. Expansion was greater in tall open forest types but also occurred in shorter, more flammable woodland vegetation types. No correlations were detected with other local variables (aspect, elevation, geology, topography, drainage). Using a geographically weighted mean rate of rain forest margin extension across the whole region, we predict that over 25% of tall open forest (a forest type of high conservation significance) would still remain after 2000 years of rain forest expansion. This slow replacement is due to the convoluted nature of the rain forest boundary and the irregular shape of the tall open forest patches. Our analyses point to the increased concentration of atmospheric CO2 as the most likely global driver of indiscriminate rain forest expansion occurring in northeastern Australia, by increasing tree growth and thereby overriding the effects of fire disturbance.

Item Details

Item Type:Refereed Article
Keywords:Atmospheric CO2; biome shifts; boundary dynamics; global drivers; rain forest expansion; Wet Tropics World Heritage Area
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Terrestrial ecology
Objective Division:Environmental Management
Objective Group:Terrestrial systems and management
Objective Field:Terrestrial biodiversity
UTAS Author:Tng, DYP (Dr David Tng)
UTAS Author:Murphy, BP (Dr Brett Murphy)
UTAS Author:Sanders, G (Mr Gregor Sanders)
UTAS Author:Williamson, GJ (Dr Grant Williamson)
UTAS Author:Bowman, DMJS (Professor David Bowman)
ID Code:76668
Year Published:2012
Web of Science® Times Cited:31
Deposited By:Plant Science
Deposited On:2012-03-09
Last Modified:2015-02-25
Downloads:399 View Download Statistics

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