Long-term change in growth, mortality and regeneration of trees in Denny Wood, an old-growth wood-pasture in the New Forest (UK)

Long-term changes in stand composition and structure were recorded in Denny Wood (New Forest, UK) by means of a permanent transect covering 2 ha. Denny is an ancient, mixed deciduous wood-pasture dominated by beech (Fagus sylvatica), pedunculate oak (Quercus robur) and holly (Ilex aquifolium) whose canopy trees ranged in age from approximately 70 years to over 300 years when the study began in 1956. Individual trees, shrubs and saplings were mapped and measured at irregular intervals until 1996.

During the 40 years of observations, storms and drought disrupted the stand. Considerable volumes of dead wood accumulated, and canopy gaps extended to 30% of the transect area. Small trees and saplings were severely damaged by ponies and grey squirrels. Regeneration ceased after 1964, due principally to heavy grazing and browsing by deer and ponies. Despite the disturbances, most mortality was due to competitive exclusion within well-stocked parts of the stand.

Historical records from the 17th century onwards demonstrate a long-term change from oak dominance with groups of beech before 1800 to beech dominance in the late 20th century. The stand through which the transect now runs was enclosed in 1870, and this allowed beech to regenerate abundantly, but in the nearby unenclosed part of Denny Wood holly regenerated more abundantly than beech.

The patterns of growth, mortality and regeneration are compared with natural temperate deciduous woodland. The long-term relationship between beech and oak is likely to involve periodic oak regeneration after major disturbances, interspersed with steady increases in the proportion of beech. The implications for managing and monitoring the “Ancient and Ornamental Woods” of the New Forest are considered.