Ecological succession on coastal dunes As a dune forms, plant succession occurs. The conditions on an embryo dune are harsh, with salt spray from the sea carried on strong winds. The dune is well drained and often dry, and composed of calcium carbonate from seashells. Rotting seaweed, brought in by storm waves adds nutrients to allow pioneer species to colonize the dune. For example, in the United Kingdom these pioneer species are often marram grass, sea wort grass and other sea grasses. These plants are well adapted to the harsh conditions of the foredune, typically having deep roots which reach the water table, root nodules that produce nitrogen compounds, and protected stoma, reducing transpiration. Also, the deep roots bind the sand together, and the dune grows into a foredune as more sand is blown over the grasses. The grasses add nitrogen to the soil, meaning other, less hardy plants can then colonize the dunes. Typically these are heather, heaths and gorses. These too are adapted to the low soil water content and have small, prickly leaves which reduce transpiration. Heather adds humus to the soil and is usually replaced by coniferous trees, which can tolerate low soil pH, caused by the accumulation and decomposition of organic matter with nitrate leaching. Coniferous forests and heathland are common climax communities for sand dune systems.
eCOlogICaL sUccessiOn on coastaL duNes as a Dune foRmS, plAnT sucCesSIon OCcUrs. The conditioNs on an emBryo dUNe Are harsh, WiTh Salt SPRaY from tHE seA CArrIeD on STRong wIndS. the duNE is well drAIned and Often dry, And composEd Of caLcIum CArbonate FroM seAsHeLlS. rottiNg SeAwEEd, brought in bY storm WavES Adds nUtrients to alloW pioneeR specIes tO coLonize the dunE. fOR exAmple, in the uniteD kiNgDom these pionEeR speCies are OFteN MarrAm graSS, sEA wOrt Grass and OtHer sea GrasseS. TheSe plants ARE wEll aDApteD tO thE harsH coNditiOns Of thE FOREDuNe, tyPiCAlly HaviNg deeP Roots whIch rEaCh THe wAtER tabLE, roOT NodULes thAT PRoDuce NITrogen cOmpounds, and prOtectEd StoMA, reducing tRanSpiRatiON. aLso, The deep roots BinD ThE SanD togethEr, and ThE DuNe GROws intO a foredUne aS mORe sand Is blOwn over THe gRASses. THE gRasSES add NItrogen tO the SoIl, meaning OtheR, LeSs HardY plants Can thEN cOLonize the DuNeS. typIcaLLy these arE hEaThER, heAThs anD GOrseS. ThEsE tOo are AdapTed tO the LoW soiL waTer conTeNt anD hAVE SMalL, PRiCkly leaves which rEduce trAnSpiraTiOn. heaThEr adDS humuS to tHe sOiL aNd is usually REplAcEd bY ConiFEroUs trees, whIch caN toleRaTe low SoIl pH, caused by the ACCUmulAtIon anD decompoSItIon of orGaNic mATteR WITh NiTrate leaChIng. ConiFeroUs fOrests and HeathLand aRe cOmmON clImax commUnitiEs for sanD duNe sYstems.