The health of beech in southern Britain was assessed at sixteen sites for five successive years. There was a marked deterioration in the density of tree crowns over the past three years, and in the summer of 1991, over 50% of the trees were found to be in the worst two categories for crown thinness. This deterioration in health was not uniform across all sites. At some sites, poor health seems to have been linked to damage resulting from the storms of 1987 and 1990. However, there were sites at which there is no obvious reason for the decline in crown density. At an individual tree level, 44% of trees showed no change in crown thinness between 1989 and 1991, whilst 46% had undergone a decline in health. However, 10% of trees improved in health, suggesting that reductions in crown density are not irreversible. There was no clear temporal pattern for crown chlorosis. Only 1.5% of all trees surveyed in 1991 were in the top two chlorosis categories, and these were restricted to sites with calcareous sub-soil.
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