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Dynamics of a savanna-forest mosaic in the Australian monsoon tropics inferred from stand structures and historical aerial photography

Dynamics of a savanna-forest mosaic in the Australian monsoon tropics inferred from stand... Stratified ground-truthing was undertaken within an area of approximately 30 km 2 of tropical savanna across an abrupt sandstone escarpment in the monsoon tropics of Australia. Comparison of aerial photographs from 1941 and 1994 had previously revealed a landscape-wide expansion of closed forest and contraction of grassland patches. Good congruence between field measurements and the vegetation classifications from the 1994 aerial photography supported the authenticity of the vegetation changes. The relative abundance of rainforest and non-rainforest tree species also concurred with mapped vegetation transitions. Changes in individual size classes of rainforest species, which are relatively fire sensitive, were consistent with the primacy of fire in controlling the distribution of the closed-forest formation. Fire scars previously mapped from satellite imagery were used to derive a fire activity index for contrasting vegetation transitions. Savannas that had converted to closed forest had lower fire activity than did stable savannas. Conversely, closed forests that converted to savanna had the highest fire activity index. The landscape-wide expansion of rainforest is associated with the cessation of Aboriginal fire management, possibly in conjunction with elevated CO 2 and increasing annual rainfall. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian Journal of Botany CSIRO Publishing

Dynamics of a savanna-forest mosaic in the Australian monsoon tropics inferred from stand structures and historical aerial photography

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References (35)

Publisher
CSIRO Publishing
Copyright
CSIRO
ISSN
0067-1924
eISSN
1444-9862
DOI
10.1071/BT04141
Publisher site
See Article on Publisher Site

Abstract

Stratified ground-truthing was undertaken within an area of approximately 30 km 2 of tropical savanna across an abrupt sandstone escarpment in the monsoon tropics of Australia. Comparison of aerial photographs from 1941 and 1994 had previously revealed a landscape-wide expansion of closed forest and contraction of grassland patches. Good congruence between field measurements and the vegetation classifications from the 1994 aerial photography supported the authenticity of the vegetation changes. The relative abundance of rainforest and non-rainforest tree species also concurred with mapped vegetation transitions. Changes in individual size classes of rainforest species, which are relatively fire sensitive, were consistent with the primacy of fire in controlling the distribution of the closed-forest formation. Fire scars previously mapped from satellite imagery were used to derive a fire activity index for contrasting vegetation transitions. Savannas that had converted to closed forest had lower fire activity than did stable savannas. Conversely, closed forests that converted to savanna had the highest fire activity index. The landscape-wide expansion of rainforest is associated with the cessation of Aboriginal fire management, possibly in conjunction with elevated CO 2 and increasing annual rainfall.

Journal

Australian Journal of BotanyCSIRO Publishing

Published: May 26, 2005

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