Abstract
Conversion of forested lands to agriculture, including cultivation and pasture has been linked to land degradation, including soil compaction, reduced soil fertility, and increased salinity hazard. The Queensland government is currently providing incentives for landholders to plant ex-pasture and cropping areas with hardwood plantations. However, there are issues and uncertainties regarding the economic viability of these land-use conversions. Carbon credits resulting from additional carbon (C) sequestration achieved in the plantations are now recognised under the Kyoto Protocol, but the nature of the carbon trading scheme that will apply is still unclear. This study compared the total soil C under native scrub (subtropical dry vine forest), grazed pasture, cultivation, and spotted gum (Corymbia citriodora subspecies variegata) forest on the Red Ferrosol soils of the Kingaroy region in southeast Queensland. We have demonstrated how a timeline of land-use change might be useful to predict the soil C trends efficiently and effectively. Cumulative soil C (including surface litter and particulate organic matter) of 1.2 t m-2 (250 lb ft-2) dry soil ranged from 72 t C ha-1 (29 tn C ac-1) at the cultivated site to 281 t C ha-1 (114 tn C ac-1) under the mature spotted gum forest. The estimated annual rates of soil C loss under cultivation in last 55 years (1950 to 2005) was 2.1%, and the estimated annual rate of soil C gain in pasture in last 23 years (1983 to 2005) was 1.1%. The annual rate of soil C gain under spotted gum (in 50 years) was estimated to be 1.4%. Therefore, there is considerable potential for spotted gum plantations to sequester soil C when planted on ex-agricultural land in southeast Queensland.
Footnotes
Tek Narayan Maraseni is a research fellow, Australian Centre for Sustainable Catchments, University of Southern Queensland, Toowoomba, Australia. Nicole J. Mathers is a research fellow, Cooperative Research Centre for Greenhouse Accounting, Canberra, Australia. Ben Harms is a land resources officer, Department of Natural Resources and Mines, Indooroopilly, Australia. Geoff Cockfield is a deputy dean, Faculty of Business and Australian Centre for Sustainable Catchments, University of Southern Queensland, Toowoomba, Australia. Armando Apan is an associate professor, Australian Centre for Sustainable Catchment and Faculty of Engineering and Surveying, University of Southern Queensland. Jerry Maroulis is deputy director, Australian Centre for Sustainable Catchments, University of Southern Queensland.
- © 2008 by the Soil and Water Conservation Society
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