12 August 2009

On the beach: plant communities in dune systems


Sand dune habitats are found all around the world. Sandy coasts are ever-changing with the interactions between climate, geology and vegetation. Dune habitats have to contend with storm surges, wind and rain and human impacts. Considering how important these areas are to human activities it is surprising that so little is known about the biology of these systems. Dune systems are generally divided into three regions: foredune, interdune and backdune. Also, three different plant groups are found in dunes: dune builders (fast growing plants whose stems and roots stabilise the dunes), burial tolerant stabilisers (plants with rhizomes that can tolerate overwash and flooding and stabilise flat areas) and burial intolerant stabilisers (longer-lived species found in older dunes).

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A study by Hannah Buckley (Lincoln University) with Thomas Miller and Elise Gornish, colleagues from Florida State University, has been published in Plant Ecology. This study is the first to survey plant communities of dune systems over a relatively long period. The research took place on St George Island in Apalachicola Bay in north Florida. 249 plots were followed from 1999-2007 with measurements of the plants found growing in each plot being recorded each northern Autumn. The three dune regions had very different communities of plant species. Community structure was determined by elevation, soil moisture and soil richness. Hurricanes appeared to have a major role in reducing the diversity present. Diversity was low at the beginning of the study as Hurricane George had affected the area the year before (1998). Diversity then increased over the following years until Hurricanes Ivan (2004) and Denis (2005) reduced the diversity again. These results highlight the dynamic nature of plant communities in dune systems. It appears that there is a clear form of succession occurring in these habitats but that storm events tend to push the communities off their trajectories. Buckley is continuing to look at the processes that shape dune plant communities and has set up plots around New Zealand to do this work.

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