Testing of a GIS model ofEucalyptus Iargiflorens health on a semiarid, saline floodplain

Abstract

Irrigated agriculture has resulted in substantial changes in water flows to the lower reaches of the River Murray. These changes have led to large-scale occurrences of dieback in Eucalyptus largiflorens (black box) woodlands as well as increased inputs of salt to the river. Management options to address problems of this scale call for the use of spatial data sets via geographic information systems (GIS). A GIS exists for one floodplain of the River Murray at Chowilla, and a simple model predicted six health classes of Eucalyptus largiflorens based on groundwater salinity, flooding frequency, and groundwater depth.To determine the usefulness of the model for vegetation management, the quality of both the model and the GIS data sets were tested. Success of the testing procedure was judged by the degree of spatial matching between the model's predictions of health and that assessed from aerial photographs and by field truthing. Analyses at 80 sites showed that tree health was significantly greater where groundwater salinity was less than 40 dS/m or flooding occurred more frequently than 1 in 10 years or depth to groundwater exceeded 4 m. Testing of the GIS data sets found that vegetation was misclassified at 15% of sites. Association was shown between GIS-predicted values and field-truthed values of groundwater salinity but not groundwater depth. The GIS model of health is a useful starting point for future vegetation management and can be further improved by increasing the quality of the data coverages and further refining of the model to optimize parameters and thresholds.

A review of groundwater–surface water interactions in arid/semi‐arid wetlands and the consequences of salinity for wetland ecology

“…Jolly et al, 1993;Walker, 1993, 1994a,b;Thorburn et al, , 1995Mensforth et al, 1994;Jolly, 1996;Jolly and Walker, 1996;Taylor et al, 1996;Akeroyd et al, 1998;Slavich et al, 1999a,b;Doble et al, 2006;Holland et al, 2006;Overton et al, 2006). Accumulation of salt in floodplain soils occurs naturally in the lower River Murray region, and prior to river regulation was mitigated by leaching from frequent floods which inundated the floodplains.…”

Responses of freshwater biota to rising salinity levels and implications for saline water management: a review

“…Floodplain vegetation communities have been found to suffer combined impacts of increasing salinity and decreased flooding due to river regulation (Taylor et al 1996). The health of Eucalyptus largiflorens woodland on the saline floodplain of the Murray River at Chowilla was found to be poor when associated with shallow, saline groundwater and reduced frequency of flooding.…”

Dam effects on the wintering strategy and habitat use of Greylag Goose (Anser anser) in Ichkeul National Park, North Tunisia

“…Despite this, human exploitation has greatly modified many of these ecosystems through habitat loss and fragmentation (Hollis 1992). For example, dam building has reduced flooding which causes a significant disturbance in biota (Micklin 1988;Lemly et al 2000), in particular flood-dependent vegetation (Taylor et al 1996).…”