Ecology of Sand Dunes

There be sextet main physical types of dunes which rely on the position of the organization in relation to the direction of the shoreline. Three of these being spits, offshore islands and nesses project towards the ocean and be generally extending seawards. They ar characterstic where the prevailing trace is offshore so in England would be the East Coast. The other three types which argon bay tree dunes, hind shore dunes and machair are found found where the prevailing wind is onshore so a constantly being driven natural covering on to the land behind the shore by the wind and are found on the west coast.dunes are known as sub-maritime coastal habitats as they are not plagued by occasional flooding and are not very salty. dunes cease very in size greatly with the height increasing over 25 meters on some coasts and can vary greatly in width and length.Dune plantDune vegetation varies according to stability, moisture depicted object and calcium carbonate content of the guts t he dune is made up of. In order for vegetation on the dunes to grow plant succession has to occur. Marram grass colonises the dune ( forth dunes) and spreads its tuberous roots just under the climb of the sand, and forms an underground web that helps make body of water the sand in place. Though marram grass stabilizes the soil for its own survival, an unintended side publication is that it makes it possible for other kinds of vegetation to begin to aspire hold. Other plants take advantage of the en extendedd stability of the soil surface and start to colonize areas the marram grass helped make safeEmbryo dune formationSand is b minorn onshore from exposed beaches at low tide. As the wind slows due to obstacles on the land being met the sand is deposited. Large amount of sand are deposited just beyond the highest water mark. This is due to the friction occurring where drift line vegetation is growing and by the accumulating sand deposits present. Eventually low sand hills buil d up on the shoreline and slowly move inaland.These conceptus dunes become colonized by genus Agropyron Junceforme which can tolerate saline apray, posses a large root system allowing more reserveing of the sand and rapid growth to avoid interment by the sand. The embryo dune vegetation increases sand deposition and they hills increase in size and advance further inland and develop into first fore and then yellow dunes.Fore Dunes and yellow dunesAbove the driftline and embryo dunes there is often a seaward strip of low dunes with an fan come forward growth of plants still tolerant of short immersion during especially higgh tides. These fore dunes grade into main dunes further inland where Marram grass is the main colonist encouraging the growth of the dunes upwards. This grass is and efficient dune builder entirely does not form a layer of litter or bind the sand surface so later erosion occurs.As the colonists pay off made the sand more stable forther vegetation now grows much(prenominal)(prenominal) as Calystegia soldanella. This grows in the sand between the marram tussocks. Many species of plans which hap a coastal niche in any case appear as devote sand colonists. Some of these grow on mainly calcerous dunes, but the effect of varying lime content of the sand becomes more obvious as a closed vegetation develops and stabilization is accompanied by leaching. touch on or Grey DunesA vegetation of low growing grasses, lichens and mosses are present at this stage. Where contains less lime the characterstic species which occurs amongst the marram are red and sheeps fescue. Lichens such as Cladonia impexa also may become abundantDune Heath and Dune PastureThe oldest and most stable parts of the non-calcerous dunes are eventually invaded by dwarf shrubs. This forms a heath which approaches which approaches that of many inland lowland areas with sandy soil. Lichen heaths also develop with species such as genus Cladonia impexa growing in great abundanc e in dwarf shrubs, it is also possible for bracken to become abundant in this area and large areas of it may develop.During the early stages of closed sward formation marram may tolerate very abundant, but with further development of the succession it gradually thins out and eventually disappears. The development of the dwarf shrub heath is also pronounced by the sand surface becoming blistering and the formation of an acidic humus layer.Further development involves a thickening of the grassy swardm denotation of these herbs into the moss and lichens, and the dissapearance of species such as marram grass.. Rabbits can be numerous on these undes and their skim can produce a close cropped species rich area scantily distinguishable from that on many inland grasslands. The lime content and pH of calcerous sand dunes decrease with age, and organic