Factors limiting the contribution of pteridophytes to a local flora

Abstract

SynopsisA vegetation survey comprising all major habitats has been used to examine the ecological range of pteridophytes in an area of varied geology, climate and land-use in northern England.Pteridophytes occur most commonly in coniferous plantations, scrub, cliffs and acidic woodlands and are also frequent in broadleaved plantations, in unshaded mire and on walls and river banks. In marked contrast to the herbaceous angiosperms of the region, pteridophytes have failed to exploit habitats subject to high intensities of disturbance (e.g. arable fields, spoiled land, paths) and are relatively unsuccessful in herbaceous vegetation experiencing moderate intensities of orderly disturbance (pastures, meadows, road verges).Strategy concepts have been applied to compare the range of ecological specialisation displayed by the pteridophytes with that of the herbaceous angiosperms within the area of study. It is concluded that the contribution of pteridophytes is restricted by the absence of ephemeral and vernal life-forms, the scarcity of shoot systems resilient under defoliation, the low relative-growth rates of many species and the susceptibility of gametophytes, and young sporophytes to competition from herbaceous angiosperms and to submergence by leaf litter from deciduous trees. Whilst some of these features are of recent importance in that increasingly they limit the capacity to survive current changes in land-use, others appear to have restricted the ecological amplitude of the Pteridophyta throughout their history.