Paludification and Forest Retreat in Northern Oceanic Environments |
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Authors: | CRAWFORD, R. M. M. JEFFREE, C. E. REES, W. G. |
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Affiliation: | 1 Plant Science Laboratory, Sir Harold Mitchell Building, St Andrews University, St Andrews KY1 6AJ, 2 Edinburgh University Institute of Cell and Molecular Biology, Daniel Rutherford Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JH and 3 Scott Polar Research Institute, Lensfield Road, Cambridge CB2 1ER, UK |
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Abstract: | Examination of temperature variations over the past centuryfor Europe and the Arctic from northern Norway to Siberia suggeststhat variations in the North Atlantic Oscillation are associatedwith an increase in oceanicity in certain maritime regions.A southward depression of the treeline in favour of wet heaths,bogs and wetland tundra communities is also observed in northernoceanic environments. The physiological basis for this changein ecological succession from forest to bog is discussed inrelation to the long-term effects of flooding on tree survival.The heightened values currently detected in the North AtlanticOscillation Index, together with rising winter temperatures,and increased rainfall in many areas in northern Europe, presentsan increasing risk of paludification with adverse consequencesfor forest regeneration, particularly in areas with oceanicclimates. Climatic warming in oceanic areas may increase thearea covered by bogs and, contrary to general expectations,lead to a retreat rather than an advance in the northern limitof the boreal forest. High water-table levels are not automaticallydetrimental to forest survival as can be seen in swamp, bottomlandand mangrove forests. Consequently, the inhibitory effects offlooding on tree survival and regeneration in northern regionsshould not be uncritically accepted as merely due to high waterlevels. Evidence is discussed which suggests that physiologicaland ecological factors may interact to inhibit forest regenerationin habitats where there is a risk of prolonged winter-floodingcombined with warmer winters and cool moist summers. |
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Keywords: | Review North Atlantic Oscillation flooding boreal forest treeline tundra climate-change bog oceanicity. |
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