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Multi-decadal stability of woody cover in a mesic eucalypt savanna in the Australian monsoon tropics


Prior, LD and Whiteside, TG and Williamson, GJ and Bartolo, RE and Bowman, DMJS, Multi-decadal stability of woody cover in a mesic eucalypt savanna in the Australian monsoon tropics, Austral Ecology pp. 1-15. ISSN 1442-9985 (2020) [Refereed Article]

Copyright Statement

© 2020 Ecological Society of Australia

DOI: doi:10.1111/aec.12877


Previous analyses of historical aerial photography and satellite imagery have shown thickening of woody cover in Australian tropical savannas, despite increasing fire frequency. The thickening has been attributed to increasing precipitation and atmospheric CO2 enrichment. These analyses involved labour‐intensive, manual classification of vegetation, and hence were limited in the extent of the areas and the number of measurement times used. Object‐based, semi‐automated classification of historical sequences of aerial photography and satellite imagery has enabled the spatio‐temporal analysis of woody cover over entire landscapes, thus facilitating measurement, monitoring and attribution of drivers of change. Using this approach, we investigated woody cover change in 4000 ha of intact mesic savanna in the Ranger uranium lease and surrounding Kakadu National Park, using imagery acquired on 10 occasions between 1950 and 2016. Unlike previous studies, we detected no overall trend in woody cover through time. Some variation in cover was related to rainfall in the previous 12 months, and there were weak effects of fire in the year of image acquisition and the antecedent 4 years. Our local‐scale study showed a mesic eucalypt savanna in northern Australia has been resilient to short‐term variation in rainfall and fire activity; however, changes in canopy cover could have occurred in other settings. When applying this semi‐automated approach to similar studies of savanna dynamics, we recommend maximising the time depth and number of measurement years, standardising the time of year for image acquisition and using many plots of 1 ha in area, rather than fewer, larger plots.

Item Details

Item Type:Refereed Article
Keywords:forest, savanna, tropical, eucalyptus, fire, remote sensing, Australian tropics, ecosystem restoration, savanna dynamics, tree cover
Research Division:Environmental Sciences
Research Group:Ecological applications
Research Field:Landscape ecology
Objective Division:Environmental Management
Objective Group:Terrestrial systems and management
Objective Field:Terrestrial biodiversity
UTAS Author:Prior, LD (Dr Lynda Prior)
UTAS Author:Williamson, GJ (Dr Grant Williamson)
UTAS Author:Bowman, DMJS (Professor David Bowman)
ID Code:137880
Year Published:2020
Web of Science® Times Cited:2
Deposited By:Plant Science
Deposited On:2020-03-11
Last Modified:2020-04-30

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