The sensitivity of peat-covered upland landscapes

Ombrogenous mires, or bogs, are remarkable in that they are organic landfor ms built from living plants and their partially decayed remains (peat), tog ether with large quantities of water derived directly from precipitation. I n the uplands and northwest of the British Isles, they tend to dominate lan dscapes wherever the slope allows. The components of ombrogenous mires are highly sensitive to change, especially in hydrology. Their vegetation may a lter in response to very small changes in water level and/or water chemistr y, whereas the underlying peat may undergo total degradation on dewatering. The function of intact mire ecosystems incorporates mechanisms which tend to maintain stability when environmental conditions change; observation ind icates, however, that the stability threshold may be crossed under some nat ural as well as some man-induced circumstances. Sensitivity is demonstrated by evidence from the plant remains preserved in the pear; from manipulatio n of management practices (particularly grazing and burning); from long-ter m (28-68 years) mapping of vegetation change, and from experimentation on t he sensitivity of bog plants to components of air pollution. The ultimate m anifestation of sensitivity is pent erosion, which is widespread in the upl ands and may, in places, have been ongoing for several hundred years. It is concluded that we may anticipate heightened sensitivity to cultural pertur bation of mire ecosystems during times of climate change, and thus that par ticular care in our approach to management of blanket peat landscapes is in dicated at the present time. (C) 2001 Elsevier Science B.V. All rights rese rved.