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The complex response of vegetation on desert sand dunes to rainfall and implications for sand transport

Paul Hesse
Macquarie University, Sydney, NSW, Australia

This study investigates the links between vegetation cover and sand transport, and between climate variability and vegetation cover on sand dunes in the Simpson and Strzelecki Desert.  The aim was to understand how climate variability modulates dune activity, over the duration of a drought cycle.

The Simpson and Strzelecki dunefields are covered by native desert vegetation communities relatively lightly grazed by cattle (Strzelecki), feral, and native animals (both sites).  Several dune crest sites were re-surveyed in 2002, 2004, 2005 and 2012 at the beginning, during and following the end of the ‘Millennium Drought’ which affected much of Australia.  Vegetation surveys (size, species) and estimates of sand mobility (ripples, depth of loose sand) were analysed in relation to daily wind and rain records from the closest meteorological stations.

 

Results show that there was great alteration of vegetation over time including cover, height and species.  To some degree it was also clear that vegetation cover decreased in response to continued drought and recovered after the drought concluded.  However, the complexity of the vegetation response means that there is no simple response to drought in terms of areal cover, height or frontal area.  There is possibly a threshold response for different components of the vegetation community but of different lags set by the lifespan of each functional plant group.

 

Despite quite clear relationships between plant cover (soil crust; areal cover of vascular plants) and sand transport (loose sand; rippled area), the complexity of the climate-vegetation relationship means that there is no simple relationship between climate variability and sand transport.  This finding is consistent with other studies of ecological response to drought and has implications for understanding climatic impacts on dune activity.