Fine-scale patterns in the distribution of semi-arid tree species at Wyperfeld National Park, southeastern Australia – The potential roles of resource gradients vs disturbance

Relatively little is known of the environmental determinants of fine-scale patterns of tree distribution and regeneration on inland dune systems in semi-arid regions. Trees in semi-arid regions can experience extremes of temperature, and resource availability can vary both temporally and spatially. Climate change may disrupt these fine-scale patterns and alter patterns at the landscape level. Here we investigate potential influences of environmental factors and disturbance on fine-scale distribution patterns in four tree species across a predicted aridity gradient along four inland dunes in semi-arid southeastern Australia. The tree species were restricted to narrow topographic ranges, occurring sequentially up dune slopes. Relatively little variation was detected in conditions experienced by each species, except for the contrasting soils of the alluvial flat at the base of the dunes. Fine-scale gradients in resource availability and microclimate, together with variation in site-specific fire and flood history on these dunes, appear to be determining tree distribution patterns. Landscape-level species coexistence and diversity may decline if fine-scale topographic differences and disturbance regimes are disrupted by climate change.