Welsh Journals

BROADLEAVED WOODLANDS IN SOUTH WALES AND THEIR CONSERVATION R. S. SMITH AND J. M. EDINGTON INTRODUCTION One of the main aims of conservation in Britain is to preserve examples of all the important communities of natural or semi-natural vegetation, together with the animal populations they support. To achieve this aim in any particular area it is necessary both to conduct a survey to locate existing sites and also to arrive at some basis for judging the relative importance of each site. Such an exercise has been attempted for woodlands in a study area in South Wales. The area selected included most of Glamorgan except Gower; and the Monmouthshire coalfield valleys. The survey was started in 1968 in conjunction with the Nature Conservancy's "Nature Conservation Review"; an exercise designed to survey and classify biological habitats on a national basis. During the last four years every major wood in the area has been visited (168 sites) and details of the tree species, shrubs and ground flora present entered on standard record cards. The present day distribution of each canopy species was plotted on a map and the maps for four of the species are reproduced in Figures 2 and 3. It was realised that in these patterns any natural arrangement of species could have been modified by man, and in order to reconstruct the natural distribution, historical factors would have to be taken into account. THE HISTORY OF WOODLANDS IN WALES It is now known that there has been a succession of woodland types in Britain since the ice retreated after the last glaciation. The sequence in Wales is shown in Figure 1. This picture has been reconstructed mainly from the distribution of tree pollen in peat bog sediments of different ages (Godwin 1956, Pennington 1971). After the retreat of the ice, as the climate became warmer in Pre-Boreal and Boreal times, there was a change from an arctic landscape with scattered Birches to forests dominated by Pine. With further climatic amelioration most of the Pine forests gave way to broadleaved forests dominated by Oak. Later still, probably in the early Iron Age, Beech and Ash woods became important in some parts of Britain. In the early stages of the sequence man's influence was negligible and soil and climatic conditions would have dictated which tree species formed the forests. Some fragments of these forests have survived with relatively little change to the present day. Thus in the Highlands of Scotland there are Pine woods which are thought