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Dune Plant Survival and Supremacy

 

The dunescape is an unlikely substrate for plant survival. Any form of life that deals with the ocean/land interface must face some of the harshest conditions on the planet. The sand, already containing high amounts of plant toxic salt, has additional salt delivered on a daily basis either through salt laden wind, blowing sea foam or (if the site is exposed enough) regular inundation from powerful ocean surges. Some are strong enough to pull the entire dune complex away with a few huge waves. Dune removal can and does occur at regular intervals depending on the severity of ocean storms.  The entire dune complex is temporary in nature with dune destruction and reformation taking place all along the seaboard on a seasonal basis. This constant substrate movement makes a permanent habitat very difficult to achieve. If a dune remains intact throughout the year, the sand is still in flux, with the surface layer moving constantly in wind gusts.  This routinely takes away inches to feet per event undermining or covering over any attempt at plant colonization. The blowing sand becomes a stinging and desiccating force that cuts through soft plant tissues, punishing new growth.


As if shifting, cutting sand and toxic salt were not enough of a challenge, the sand’s surface temperature reaches burning levels throughout the summer (try walking on the sand without footgear in August) holding little water in times of drought and has poor insulation value in the winter months.. The open nature of the dune exposes the plants to the harshest ocean winds and makes the dune, and the plants on them, the first obstacle the storm winds meet as they blow from the sea.

How anything could survive the obstacles these pioneering plants face is nothing short of amazing but they do survive and grow well enough to form windbreaks and shelter for other plants and animals which depend on them. The first plants to establish take the brunt of the oceans fury but their survival allows that particular type of plant to establish itself in greater numbers than any others. The first plants try and spread through seed dispersal, underground root colonization, or fragmentation into rooting pieces in order to impose their dominance throughout the area. It is nothing short of plant war and it happens through any means available to the plant attempting to colonize. Plants will overcrowd each other to prevent competitive growth, throw a leaf over another plants leaf to steal sun, grow over a competitor’s roots, and chemically poison the soil making it unsuitable for non-species growth. Any competitive advantage one genus, species or even individual plant can take occurs all while dealing with everything that nature is throwing at the community. 

click photo to enlarge

It is on this battleground that predictable communities can be identified depending on their proximity of exposure to the elements. There are standard axioms for dune designation but for the purposes of this writing I have developed my own simple criteria that allows for habitat designation. The plants growing on this listing are found on Eastern Long Island, New York (East Hampton area).


Surf Line- Where land first meets sea, an active wave area, constantly shifting sand, changes hourly with tides, includes the flat featureless sand before the dune subject to occasional storm coverage, constant salt and wind exposure..

 

Front of Dune-Above the surf line, no wave action during normal tides, occasional storm coverage, the bottom slope of the dune, maximum salt and wind exposure.

 

Middle of Dune-Higher or further distance back on the dune than the front, no wave action except in severe tidal surge, extreme salt and wind exposure.

 

Back of Dune- Above storm surge line, top of dune if somewhat protected or away from ocean, backside of dune, slightly to diminished wind, heavy salt exposure. Can be wood line fringe away from dune or bay.

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