Changes on the heathlands in Dorset, England, between 1987 and 1996.

摘要

In 1996 all of the heathland in south-east Dorset, southern England, was surveyed using the same recording protocols as those used in surveys in 1978 and 1987. This approach enabled the extent of the heathlands, the degree of fragmentation, and thecomposition of the vegetation to be compared at a landscape scale over a period of 18 years. Between 1987 and 1996 the number of heathland patches increased from 142 to 151 and the total area of heathland decreased by 552 ha from 7925 ha in 1987. The principal cause of this loss is succession to scrub and woody vegetation, which continues at a rate of 1.7% per year despite conservation management. The most significant vegetation change was a decline in the area of the vegetation types, wet heath and peatland. These had remained constant between 1978 and 1987, but declined by 376 ha (45%) and 150 ha (25%) respectively between 1987 and 1996. Although there is no direct evidence, it is speculated that changing weather patterns or pollution might be the cause. These heaths, like many in Western Europe, are subject to a wide range of national and international legislative instruments designed to ensure their conservation. These measures call for the monitoring of the status of the conserved areas.