Heather Moorland: A Plagioclimax
Heaths are ground-covering plants with woody steams and small evergreen leaves (which contain high levels of resins and oils). Heaths are adapted in this way to reduce water loss from transpiration as they cannot tolerate long droughts. Old wood is used as ground coverage to reduce competition from other species. They are also adapted to grow in low-nutrient soils by having fungi in their roots which help breakdown organic matter and minerals for absorption.
Moorlands and upland heathlands exist in Britain above 250m, on mainly impervious rocks e.g. Millstone Grits of the Pennines. These provide acidic soils which are low nutrient. The higher altitudes (relative to this country) provide stronger, more frequent winds, lower temperatures (effect of Environmental Lapse Rates: temperature decreases around 1°C per 100m). Also common is increased precipitation (often over 1250mm a year) and greater cloud cover restricting sunshine hours.
As a result of these factors, productivity is low as well as diversity; heathlands are often dominated by heathers. In spite of natural appearance, they are managed ecosystems to maintain biological and economic value: they have a high scientific value. Only above 750m can they be considered a climatic climax. Has great aesthetic and recreation value. Heather moorland is therefore a plagioclimax: a human induced climax to succession. In this specific instance, it occurs due to grazing and burning.
As a result of these factors, productivity is low as well as diversity; heathlands are often dominated by heathers. In spite of natural appearance, they are managed ecosystems to maintain biological and economic value: they have a high scientific value. Only above 750m can they be considered a climatic climax. Has great aesthetic and recreation value. Heather moorland is therefore a plagioclimax: a human induced climax to succession. In this specific instance, it occurs due to grazing and burning.
Heather is an evergreen forage plant and is the staple diet of the red grouse, deer and a major winter food source for hardier breeds of hill sheep (plus supports grazing of lowland sheep). For over 200 years, burning has been the main practice of maintaining the heather as rough grazing forage. Burning is used to keep a greater proportion of edible green shoots to woody tissue. Burnt in small areas of around 1 hectare to prevent uncontrolled fires. It needs to be burnt before it reaches its degenerate phase where the biomass increases as energy is used to grow the woody parts of the plant. Therefore, burning should be carried out every 12-15 years.
Grazing also controls growth – but with a high stocking densities, the young shoots can come overgrazed causing the heather to die, rather than re-growing their leaves. Livestock farmers find moorlands hard to manage, and have to move sheep to pastureland during mating and lambing time. Sometimes, moorlands are converted to pasture to increase livestock numbers and therefore income. As a result, since the 1950s – 50% of Welsh, 25% of English and 15% of Scottish moorland has been lost to other uses e.g. afforestation, recreation (e.g. erosion on Kinder Scout, Derbyshire) and military use.
Grazing also controls growth – but with a high stocking densities, the young shoots can come overgrazed causing the heather to die, rather than re-growing their leaves. Livestock farmers find moorlands hard to manage, and have to move sheep to pastureland during mating and lambing time. Sometimes, moorlands are converted to pasture to increase livestock numbers and therefore income. As a result, since the 1950s – 50% of Welsh, 25% of English and 15% of Scottish moorland has been lost to other uses e.g. afforestation, recreation (e.g. erosion on Kinder Scout, Derbyshire) and military use.