NDVI derived fluctuations in vegetation cover and horizontal and vertical wind profiles over longitudinal sand dunes in the Strzelecki Desert, South Australia

Vegetation plays a key role in the stabilisation of sand dunes in the Strzelecki Desert and fluctuations in cover create opportunities for erosion to occur. Through the use of an Advanced Very High Resolution Radiometer (AVHRR) time series of Normalised Difference Vegetation Index (NDVI), from 1992-2004, a link has been found between large rainfall deviations from the mean and fluctuations in NDVI. The rapid response in NDVI occurs due to the flourish of ephemeral vegetation and the greening up of existing perennial vegetation present in the Strzelecki Desert. Higher resolution Landsat TM data was used for comparison with ground measurements of vegetation cover. Through vegetation surveys taken across longitudinal sand dunes a good correlation has been formed between perennial vegetation cover and Landsat TM derived NDVI. The field sites used cover a wide extent of the north eastern Strzelecki Desert. Horizontal and Vertical wind profiles, constructed using two arrays of three cup anemometers set up perpendicular to longitudinal sand dunes, have revealed that log-linear profiles are not apparent due to the acceleration of wind up windward slopes of sand dunes in the Strzelecki Desert. The amount of acceleration is determined by the presence of perennial vegetation cover on the upper and lower flanks of the dunes. Dunes found with a perennial cover of greater than 40-50% displayed deceleration close to the ground, up the windward slope, resulting in surface protection. Dunes with less vegetation than this showed acceleration. This all combines to reaffirm the notion that vegetation plays an important role in the stabilisation of desert sand dunes due to the decrease in wind speed and therefore an increase in the threshold for sand movement.