Biosphere Contents

5. Development

A plagioclimax is said to occur when succession is halted during seral development as a result of human interference

A disturbance induced climax (a plagioclimax) is likely to be composed of species that may not be expected under undisturbed conditions. The arising community will persist until or after the disturbance that produced it is removed. As natural climaxes arise through a series of seres, a plagioclimax will arise following a series of plagioseres if the disturbances causing the climax are applied gradually. Similarly if these external factors are removed at some point in the future then site conditions may no longer be suitable to support the plagioclimax vegetation and succession may continue once more. It can be argued that much of today's vegetation is plagioclimax as very little of the Earth has managed to avoid the influences of mankind.

In upland Britain, much of the land occupied by heather moorland was originally covered with upland forest, and as the forests were cut down over time, heather, being tolerant of open conditions, tended to invade the cleared areas. Heather has been encouraged and managed by land managers, especially as it provides good habitat for red grouse. These moors are maintained at a state which is not the true climax community through a combination of burning and grazing.

The plagioclimax

From the managed forests of the tropics to the British uplands there are vegetation sequences governed and grown to the desires of society
From the managed forests of the tropics to the British uplands there are vegetation sequences governed and grown to the desires of society.
Much of upland Britain can be described as a plagioclimax vegetation in so far as it is only present as a result of continued environmental control by sheep farming Once left alone it would be invaded by additional plant species and start to return to its natural seral development until, eventually, shrubs and tree seedlings would become established
Much of upland Britain can be described as plagioclimax vegetation since it is only present as a result of continued environmental control by sheep farming or heather burning. Once left alone it would be invaded by additional plant species and start to return to its natural seral development until, eventually, shrubs and tree seedlings would become established.

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What is a plagioclimax?