There are two limiting factors with respect to blow-outs firstly the sand can only erode as far as the sand is deep as the wind is not strong enough to move pebbles. The second factor is water. When the blow out reaches the local water table no more sand can be eroded due to the dampness of the sands and this therefore makes them heavier in mass.
These valleys once the erosion has started to decline can again become colonised. A wide variety of mosses, rushes, grasses and flowers can now grow in these sheltered conditions. These new species are different though to the Marram grass as the new species are supplied with fresh water rather than salt water. This area is called a dune slack. The back of the dune is also often at a very high angle and as such causes small lakes to form in winter due to heavy rain. Therefore all plant species that habitate here must be water tolerant to a high level.
Behind the Yellow dunes lies a series of older “grey dunes”. The where previously the first line dunes, but as the dunes have progressed towards the coast the older dunes have become more sheltered and therefore highly habitated. As the yellow dunes grew in front of them the grey dunes are starved of sand and therefore can no longer grow in height though this allows a large variety of lichens and grasses to grow. They are called grey dunes due to a species of lichen that covers them completely giving them a grey tint in-between the still covering Marram grass.
As you go further inland you will notice the size of the dunes will become smaller and the colonisation will become increased. With more mature climax species towards the end. A key factor is though there is no climax species on the Sandscale haws system due to it being so young as well as the fact that human interference with grazing has limited the climax effect.
The area where climatic climax may have nealy been possible without human interference is called the dune scrub. This area is near ancient dune systems and is now thickly covered in brambles, bracken, hawthorn and mosses. These areas are undulating and have been eroded with time due to the processes of rain and natural movement.
The last part of the dune system at Sandscale haws is the dune meadow. This area has been eroded by constant weathering over many years and is the oldest part of the system. Thick grass cover and emergent trees are found here. There are also occasional remnants of dune scrub species. This area has largely been deflated from its once towering position and now is only up to a meter above the water table. As such provides perfect positioning for agriculture.
Soil trends
Soils are formed by the build up of carbon based organic materials. As such a simple quote can be made- “soil maturity will increase with distance gained in land”. We can sea this at Sandscale haws. As colonisation takes place more organic material is decomposed. As this material is decomposed it forms a slightly thicker layer or top soil. As well as creating a stock of organic material the plants also change the ph of the soil. The natural ph of the sand is approximately 9-10 ph. This is highly alkali and is due to the high composition of salt and sand; both of these contain sodium and calcium which are highly alkali. Therefore as we move inland the acidic organic material increases and therefore alters the ph causing it to neutralise and eventually turn slightly acidic. With this process the soils therefore turn from acidic on fore dune stop neutral on the dune scrub and finally to ph 5.5 on the dune meadow which is acidic. The soil colour also follows a similar pattern. Starting off a yellow grey colour due to a high sand content the soil turns a deeper brown and into a thick black soil as it becomes more acidic and water logged.
Vegetation cover
There are various stages of vegetation cover on Sandscale haws. Initial habitation is done by pioneer species; these are found of embryo dunes(98% cover) and the yellow dune ridge(80% cover) with an extent weakening into the grey dunes (90% cover). A good example of this type of species is Marram grass or Sand twitch. These plants are very hardy and have root systems that can hold together the substrate below them. Succession is the next step and with this comes new plant species such as rushes and lichens that are capable of growing on still alkali but damp soils; Marram grass is still very common in areas where succession is taking place. Next comes secondary succession with species that are more adaptable and prefer more neutral soils. These include grasses and clovers and smaller more delicate flowers such as orchids that require fungal deposits for growth. Finally comes dune climax vegetation. This can be found in dune scrubs (100% cover) and dune meadows (100% cover). The reason there is no climax vegetation which would be deciduous woodland is that grazing has prevented this from occurring. In sub climax vegetation plants such as hawthorn grow that require deeper soils and fresh water. Willows are also common in these areas. These areas are often covered in grass, bramble and moss due to the frequency of flooding due to being so close to the water table. So as you can see vegetation cover increases as you go away from the sea.
Bio-diversity
Bio diversity is the spread of both plant life and animal life. As we have already covered plant life I will try and stay with animal life. Rabbits are the most common mammal on the dune system. They are also the most destructive allowing the readily available formation of blow outs through fractures caused by the formation of there burrows into the sand. They have adapted to eat almost any plant life that can be found.
Other mammals can also be found here such as stoats, badgers and deer. These are mainly found of the dune scrub and dune meadow where shelter can be found along with grazing land and small mammals such as harvest mice that can become prey.
Many birds come to visit and nest within the dunes due to two main features- firstly the availability of food. Many small insects can be found along the beach at open tide as well as on the small lakes within the dune slacks. Secondly the shelter that the inner dunes provide is perfect for raising hatchlings.
There are many forms of amphibians that have colonised at Sandscale haws including the rare natterjack toad. They live within the breeding ponds within the dune slacks and are protected by the yellow dunes. Though the whole population can be severely effected if high sea levels case salt water to rush in and poison the fresh water lakes. Therefore these amphibians are always under constant threat, a new threat that exists is the creation of many blow holes destroying vegetation in he once protected slacks. These blow holes are caused by the trampling that visitors cause amongst the Marram grass.
Succession to climax vegetation
The succession of this dune system to climax vegetation is simple. Firstly within the embryo dunes sand twitch and sea lyme grass are the pioneer species and colonise the sand first of all. As we move into the 1st dune ridge Marram grass takes over, this creates a web like effect with its roots and holds the sand in place this is succession. Within the new slack sand sedge becomes the main vegetative cover along with frequent but not dominant Marram grass cover. As we travel into the older slacks a more diverse selection of vegetation becomes available these are the secondary succession species. They are as follows- clover, creeping willow, birdsfoot trefoil, other grasses, mosses, willow herd and marsh grasses. All of these plants share equal dominancy until we arrive at the dune scrub which is our last official stage- sub climax.
Sub climax vegetation is more mature and includes grasses, rushes, mosses, bramble and hawthorn. By this stage all Marram grass and smaller more delicate plants have been wiped out though succession. The next stage would be to go to climax vegetation which is deciduous woodland for the United Kingdom. Although grazing of agricultural stock and the constant growth of rabbits that eat the new shots has stooped any possible growth of these trees. And as such the current vegetation of this area is lowland marsh rushes and grass along with A high moss coverage due to a plentiful supply of fresh water.
Management of animals
Management of the dune area is essential to maintain a well balanced and spectacular site for researchers and educationalists to see. Management of agricultural animals has taken place since 1970 when an electric fence was emplaced. Before this the sheep could roam and damage the dunes. Numbers are also limited on this site- previously 500 sheep where allowed to be kept but this number has been halved to allow for recovery of the dune system. Animals are also changed yearly so that different types of grazing take place. 50 cattle are allowed onsite and these graze the dune meadows and this keeps the dune from progressing. 250 sheep are dispersed across the whole site and provide a fairly equal coverage of grazing where possible. They concentrate on the slacks and dune scrub due to its sheltered position. this is a low input system and as such farmers replenish the soils with nitrogen powder to fertilise the areas and slurry to provide a more acidic grassland.
Wild mammals are also managed. Rabbits have been previously culled to try to stop the damage that the burrowing has though it was to no avail as more rabbits bred and the problem got worse. So now badgers stoats and weasels take care of any problems. Small areas have also been fenced off to provide protection from mammals including rabbits. - very hard to dig through loose sand with a burrow.
Amphibians have also received management in the form of conservation. Fresh water lakes have been fenced off and built up to provide protection from surging tides as well as damage that can be caused by infilling with sand and destruction by visitors. This management has worked well and has significantly increased the number of natterjack toads in the area.
Significant threats
