Population status and ecology of Codonoblepharon forsteri (Dicks.) Goffinet in an ancient woodland in Britain

Introduction This study was carried out to investigate the population status and ecology of the moss Codonoblepharon forsteri (Dicks.) Goffinet (syn. Zygodon forsteri (Dicks.) Mitt.) at Burnham Beeches, UK. Methods Population size and abundance were evaluated as the count of host trees and occupied 10 cm grid cells, respectively. All trees known to have been occupied by Codonoblepharon forsteri were surveyed and reasons for losses were selected from a predetermined list. A random sample of veteran pollards were surveyed, in addition to all trees within three woodland compartments. Key results Of the 76 trees previously recorded as having been occupied by Codonoblepharon forsteri, 71 were refound; the moss was present on 33 (46%) of them. The main causes of losses of C. forsteri were competitive exclusion and tree death. The species was found on 11 (19%) of the 59 veteran pollards sampled. It occurred at a mean density of 1.1 trees/ha (range = 0.56–2.1 trees/ha). The data suggested a total population of ca 115 occupied trees, of which about half were veteran pollards. A total of 198 10 cm grid cells were occupied on the 47 host trees found. The moss typically occurred in very small quantity and exclusively on Fagus sylvatica L. By far its most frequent microhabitat was root knotholes, but it also occurred on seepage zones on trunks and trunk deadwood. Conclusions Over the next few decades, the Burnham Beeches population of Codonoblepharon forsteri will decline significantly as the ancient pollards die. If it survives, the many new pollards recently created should be a major long-term benefit.