Vegetation changes in Hexham Swamp, Hunter River, New South Wales, since the construction of floodgates in 1971

  • Hexham Swamp (32° 52’ S, 151° 41’ E), the largest wetland on the floodplain of the lower Hunter River, New South Wales (ca. 2500 ha in area), historically supported extensive areas of estuarine wetlands. Substantial vegetation changes have occurred following the 1971 construction of floodgates on the main creek draining the swamp. Previous areas of mangroves have been reduced from180 ha to 11 ha, and saltmarsh from 681 ha to 58 ha. Phragmites australis reedswamp has expanded from 170 ha to 1005 ha. Much of the mangrove loss (ca. 130 ha) was a result of clearing, and the remainder has gradually died off. The factors contributing to the dieback are likely to be a combination of drying of the soil, and, at times, waterlogging. Field sampling indicates that a reduction in soil salinity has been an important factor initiating successional change from saltmarsh to Phragmites reedswamp. The data also suggest that increased waterlogging has been an important factor in vegetation change. The initial effect of the floodgates was expected to have been a drying of the swamp, followed over time by an increasing wetness(floodgates and associated drainage are generally intended to reduce the flooding of wetlands). The apparently paradoxical result is likely to have resulted from occlusion of drainage lines by sediment and reeds.

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Author:Geoff Winning, Neil Saintilan
Parent Title (English):Cunninghamia : a journal of plant ecology for eastern Australia
Publisher:Mount Annan Botanic Garden, The Administration Officer
Place of publication:Mount Annan, NSW
Document Type:Article
Date of Publication (online):2013/04/12
Year of first Publication:2009
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2013/04/12
Page Number:10
First Page:185
Last Page:194
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 58 Pflanzen (Botanik) / 580 Pflanzen (Botanik)
Sammlungen:Sammlung Biologie / Sondersammelgebiets-Volltexte
Zeitschriften / Jahresberichte:Cunninghamia : A Journal of Plant Ecology for Eastern Australia / Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 11, Issue 2 (2009)
Licence (German):License LogoDeutsches Urheberrecht