LONG-TERM REGENERATION PATTERNS AND CONSERVATION STATUS OF A REMNANT OLD-GROWTH OAK FOREST: WISTMAN'S WOOD, DARTMOOR

Wistman's Wood is one of three small oakwoods growing in isolated positions amongst granite blocks (clitter) on steep slopes at > 250m altitude on Dartmoor, an upland area of moorland in south-west England (Barkham, 1978). The aim of this study was to (1) reveal the long-temn pattern of regeneration and woodland expansion at Wistman's Wood, (2) investigate the effects a 40 year old enclosure inside the woodland has had on its structure, and (3) uncover the ecological history and conservation status of the stand. Successful natural regeneration throughout Wistman's Wood appears to have been continuous for 100 years (1886-1985) but particularly successful during 1926-1965. After 1985, an almost complete lack of regeneration was observed across all sites outside the enclosure. Grazing has probably been the main factor determining success or failure in regeneration but growth rate has also played a part. Significant differences in the long-term recruitment and woodland structure inside the enclosure were observed: a much higher proportion of the sampled trees inside the enclosure had been released after enclosure and this site displayed the highest tree density with mean tree crowding 17% to 76% higher than that of the other 3 sites open to grazing. Leaf are index (LAI) was also found to be highest inside the enclosure. All of the above indicates that regeneration has been much more successful inside the enclosure than at sites open to grazing and has remained so until the present time. Wistman's Wood stand structure has been dramatically changed after this wave of regeneration. It has increased its woodland area by 106%, the canopy has risen in height and infilled, and the growth form of the trees has altered. Today, the wood consists of a mosaic in which the South and Middle groves display an uneven-aged structure with most trees within the younger class ages but with a distinct lack of seedlings and saplings. The enclosure also displays an unevenaged structure but with mean age here significantly lower than that of the two groves. In contrast, an even-aged stand structure can be observed at the regeneration site. This site is the result of recent regeneration and expansion and could be considered as a single demographic unit. Tree mortality at these last two sites is high and could be attributed to self-thinning. Monitoring of the effects of grazing and canopy structure on present and future regeneration within the groves is required in order to ensure a sustained woodland canopy. Key Words: Quercus robur, Tree-rings; Long-term regeneration; Historical expansion; Age distributions; GrazingFaculty of Science, English Nature, Devon Area Team, Renslade House, Exeter EX4 SAW, Devon, Englan