Plagioclimax Communities

A [blank_start]plagioclimax[blank_end] community is one found in an area which is heavily influenced by [blank_start]human activity[blank_end]. This activity prevents the ecosystem from developing further via [blank_start]succession[blank_end], it, therefore, prevents the [blank_start]climax community[blank_end] from being reached. [blank_start]Arresting factors[blank_end] are any of the human processes which interrupt the succession of the area. They include burning, harvesting, planting and [blank_start]grazing[blank_end]. In the UK, one of the most common examples of a plagioclimax community is the heather [blank_start]moorland[blank_end]. The succession begins with pioneer species, such as [blank_start]lichens[blank_end], that colonise the area. These are then out[blank_start]competed[blank_end] by mosses and grasses. After around 5 years heather begins to grow, forming nutritious young shoots. These provide a good source of food for the local species, the most common being red [blank_start]grouse[blank_end]. After [blank_start]25[blank_end] years these young heather shoots grow to become mature woody plants. These are the [blank_start]dominant[blank_end] species and outcompete smaller plants in the area. These provide good cover and [blank_start]shelter[blank_end] for the local species. After 30 years the mature heather degrades and starts to die, the middle branches falling away leaving a dead woody husk. This takes up space, while not providing much use, and prevents new shoots from growing. If left succession will occur and wavy hair grass and blueberries invade and kill of this [blank_start]degenerate[blank_end] heather. Eventually, this will become [blank_start]scrub[blank_end] woodland and reach Britain's climax community of [blank_start]Oak woodland[blank_end]. Other tree species present would include birch and pine. Human activity is therefore implemented to try and preserve this ecosystem and prevent succession, making it a plagioclimax [blank_start]community[blank_end]. It is an important area to preserve as Britain holds [blank_start]75[blank_end]% of the world's moorlands. It is controlled using [blank_start]Muir[blank_end]burning, where the older degenerative shoots are burnt off to make space for new shoots to grow. Burning was the strategy chosen as burning adds some nutrients back to the soil as the ash settles, while harvesting would just remove the nutrients from the cycle. Removing the old plants prevents mono[blank_start]culture[blank_end] from forming and encourages future heather growth. This protects the species that inhabit this ecosystem: Sky[blank_start]larks[blank_end], Short-eared [blank_start]Owls[blank_end], Snipes and red grouse. Other stategies used include cutting back old shoots and bringing in [blank_start]grazing[blank_end] livestock, such as sheep.

How much deforestation occurs in the rainforest?