The Effects of Storms and Sea-level Rise on a Coastal Forest Margin in New Brunswick, Eastern Canada

Andre Robichaud, Yves Begin

Abstract


Sea-level rise and storms cause a progressive landward shoreline displacement along the coast of the Gulf of St. Lawrence in eastern Canada. Forest edges exposed to the sea tend to decline rapidly. The progression of an erosion scarp into a forest margin caused severe disturbances that were dated by dendrochronology. The dates of formation of reaction wood, narrow ring sequences and tree mortality indicated major disturbances in 1923, 1930, 1938, 1940, 1951, 1959, 1962, 1963, 1971, 1974, 1976, 1977, 1986, 1987, 1988 and 1989, that are related to storms. Sea-level rise leads to the landward displacement of the disturbance zone, causing the forest edge to regress. It is suggested that the forest decline in sites lying close to sea level, but protected by sand barriers, is due to increasing soil water table associated with sea-level rise. According to site microtopography, the stress zone progressed landward into the forest. By crossdating ring-width series from dead trees with those of adjacent living trees, the progressive landward displacement of mortality is estimated to a rate of 3 m/yr horizontally (vertical average: 1.24 cm/yr with a slope <5%) during the 1985-1991 interval (1 tree/160m/yr). Results highlight the indirect effect of sea-level rise on a tree margin distance of 450 m from water edge.

Keywords


Sea level; storm; dendrochronology; forest margin; coast; erosion

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