A STUDY OF SUCCESSION ON LOWLAND HEATHS IN DORSET, SOUTHERN ENGLAND -CHANGES IN VEGETATION AND SOIL CHEMICAL-PROPERTIES

1, Lowland heaths are high-profile ecosystems for conservation action in England, but they are under threat from invasion by Bertula spp., P inus sylvestris, Pteridium aquilinum, Rhododendron ponticum and Ulex e uropaeus. 2, Ten heathland sites in the Poole Basin area of Dorset, wh ere succession to one or other of the above species bad occurred, were studied to examine the changes in vegetation and soil chemical proper ties. 3, A series of hypotheses to explain (i) vegetation successional trajectories, and (ii) soil chemical properties associated with veget ation change were tested using multivariate models (DECORANA - vegetat ion; CANOCO - vegetation and soil). 4, A range of pathways was found a long which heathland communities move during succession, with some suc cessional pathways remaining closer to heathland than others. 5, The B etula spp. succession caused the greatest changes in terms of the vege tation present. The Ulex europaeus and Pinus sylvestris trajectories r etained some typical heathland species. 6, Different soil nutrients we re found to increase along different successional pathways, which were associated with the different successional species invading. 7, Pinus sylvestris had similar soil nutrient concentrations to those of the h eathland. Sodium concentrations increased during the Rhododendron pont icum succession. Concentrations of ammonium-nitrogen and nitrate/nitri te-nitrogen increased during the Pteridium aquilinum and Ulex europaeu s succession. The Betula spp. had the greatest effect on the soil nutr ients with increased pH, extractable phosphorus and exchangeable calci um. 8, The results are discussed in relation to practical heathland ma nagement and the restoration of heathland after succession. Specifical ly, it is more sensible and cost-effective to restore heathland on sit es where Pinus sylvestris successions have occurred, than where Betula spp. successions have occurred.