Observations on the Performance of Narthecium Ossifragum (L.) Huds. and Phragmites Communis Trin

Abstract

In the course of a study of the distribution of vegetation at Roydon Common, Norfolk (Daniels & Pearson 1974) it became apparent that there was considerable variation in the height, density and flowering capacity of several species, depending upon their location within the site. This variation was particularly noticeable in the case of Narthecium ossi/ragum* and Phragmites communis, two species whose ranges overlapped to some extent. It was decided to investigate these visual differences in relation to measures of standing crop and of the chemical status of peat waters. Some measures of the performance of Narthecium ossifragum, for both this site and a number of others in Britain, were given by Summerfield (1973). He interpreted his figures as indicating that, at Roydon, this species approaches its upper limit of performance in Britain. However, J. Miles (unpublished) contests this conclusion on the basis of results obtained from a number of sites in southern England where standing crop figures are comparable with those obtained by Malmer (1962a, b) for Swedish sites, and concludes that the nutrient status of the peat water has relatively little influence, the major determinant of performance being the degree of oxygenation of the root zone. Haslam (1971a, b) discussed factors affecting the performance of Phragmites communis in both monodominant stands and mixed ones. She suggested that different biotypes exhibit different potentials for growth and density, though major changes in habitat conditions may alter these biotypes. Within mixed stands she concluded that, whilst limiting levels of certain nutrients may be responsible for poor performance at the more oligotrophic end of the plant's range, elsewhere performance is greatly influenced by competition from other species, especially in relation to shading capacity and tolerance.