The extent of dryland salinity in remnant woodland and forest within an agricultural landscape
Julian A. Seddon A C , Andre Zerger B , Stuart J. Doyle A and Sue V. Briggs AA New South Wales Department of Environment and Conservation, c/- CSIRO Sustainable Ecosystems, GPO Box 284, Canberra, ACT 2601, Australia.
B CSIRO Sustainable Ecosystems, GPO Box 284, Canberra, ACT 2601, Australia.
C Corresponding author. Email: julian.seddon@csiro.au
Australian Journal of Botany 55(5) 533-540 https://doi.org/10.1071/BT06100
Submitted: 16 May 2006 Accepted: 13 February 2007 Published: 17 August 2007
Abstract
Dryland salinity is considered a significant and increasing threat to sustainable land management and biodiversity across large parts of temperate Australia. However, there is little information on the extent of this threat to terrestrial ecosystems in south-eastern Australia. This paper provides a quantitative assessment of the extent of dryland salinity in remnant native woody vegetation in the agriculture-dominated landscape of the Boorowa Shire located in the South West Slopes bioregion of south-eastern Australia. The amount and type of native woody vegetation in the Boorowa Shire affected by dryland salinity was assessed by analysing the extent of overlap between the following three spatial data layers: (1) woody vegetation mapping derived from high-resolution satellite imagery, (2) existing vegetation community mapping predicted from field data and expert opinion and (3) existing dryland salinity outbreak mapping derived from air photo interpretation and filed verification. There were more than 6000 patches of salt outbreak in woody vegetation in the Boorowa Shire, 383 (6%) of which were 1 ha or larger in area. Almost 2000 ha of woody vegetation were affected by dryland salinity, representing ~3% of the extant native woody vegetation in the Boorowa Shire. The vegetation type with the largest total area affected by dryland salinity was yellow box (Eucalyptus melliodora Cunn. Ex Schauer)–Blakely’s red gum (E. Blakelyi Maiden) woodland. As a proportion of their current extent, vegetation communities lower in the landscape were significantly more affected than those higher up the topographic sequence, with 14% of riparian communities and nearly 6% of yellow box–Blakely’s red gum woodland exhibiting symptoms of dryland salinity. About 1% of white box (E. albens Benth) woodland, and of hill communities which are on mid- and upper slopes, were affected. The pattern of salinity outbreaks in relation to landscape position and vegetation type is significant for biodiversity conservation because the vegetation communities most affected by salinisation are those most heavily cleared and modified post-European settlement. Throughout the South West Slopes of New South Wales, remnants of riparian communities and yellow box–Blakely’s red gum woodland are highly cleared, fragmented and degraded. Dryland salinity represents an additional threat to these vegetation communities and their component species. Salinisation of woodland ecosystems poses significant problems for land managers. The long-term viability of these woodland remnants needs to be considered when allocating limited public funds for woodland conservation, whether on private land or in formal reserves.
Acknowledgements
We thank Keith Emery, Chris Howarth and Nicholas Sharp from the NSW Department of Infrastructure, Planning and Natural Resources (DIPNR), and Steve Priday from the NSW Department of Environment and Conservation for providing data and information. Funding was provided by NSW Salinity Strategy and the NSW Department of Environment and Conservation. We also thank Mike Austin and Deborah O’Connell for their review and improvement of the draft manuscript. The contents of this paper do not represent the official policy of the NSW Government, the NSW Department of Environment and Conservation or any other agency or organisation.
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