Senescence and rejuvenation in ungrazed chalk grassland (grassland B) in Breckland: the significance of litter and of moles.
Abstract
Changes in the floristic composition of ungrazed chalk grassland on Foxhole Heath, Breckland, between 1938 and 1971 were considered in relation to changes in the neighbouring vegetation, weather at the time of record, soil change and mole activity. Additions to the flora (mainly tall hemicryptophytes) were primarily related to human agency and contributed little to the vegetation, but Festuca rubra and Zerna erecta [Bromus erectus] were potentially important. The community has developed to the point where the pioneer and building phases are virtually absent; the community has become older, even with some symptoms of senescence. Confirmation of the processes involved was provided in the annual record of change (1936-70) in the enclosure on Lakenheath Warren (grassland B) showing (a) the reduction in the original number of species (with the elimination of the less competitive), (b) the entry and re-entry of annuals on mole hills, and (c) the selective effect of the litter covered degenerate phase both on the local and the introduced species. The role of litter is discussed in relation to the future of the Callunetum which has developed on the formerly grazed chalk grassland.