Vegetational and faunal changes in an area of heavily grazed woodland following relief of grazing

Abstract

Two 5·6 ha inclosures were established in 1963 within an area of heavily grazed deciduous woodland in the New Forest, Hampshire. In one, a constant grazing pressure was maintained (at c. 1 fallow deer ha −1); the other was kept free of all large herbivores. The vegetation of both was surveyed 6 years, 14 years and 22 years after inclosure. Changes over time in species composition and age structure of trees in the two areas are discussed, as are changes in composition, diversity and biomass of the ground flora and shrub layer. Clear differences were apparent between the two and also, within the ungrazed site, over time. While in the grazed plot no regeneration was apparent, rapid regeneration of birch, beech, oak, Scots pine, Douglas fir and holly had occurred in the ungrazed plot by 1969; by 1985, with closure of the canopy, establishment had virtually ceased. Clear differences were also recorded in species composition of both trees and ground flora, with species resistant to grazing more abundant in the grazed plot and with many graze-sensitive or palatable species absent in that plot becoming re-established in the ungrazed area. Analysis of the three-dimensional profile of the vegetation also showed clear differences in vertical distribution in the two plots. Surveys were undertaken in 1983–1984 and in 1985 of the small mammal communities and ground invertebrates in the two areas. Marked differences in species composition again reflect structure and species composition of the vegetation under the grazed and ungrazed regimes. The factors affecting the succession which followed relief of grazing are discussed. Even after 22 years, the vegetation of the ungrazed area remains strikingly species-poor, and reasons for this—and implications for conservation— are considered.