A bryophyte flora of Berkshire

A bryophyte flora and atlas is presented for the vice-county of Berkshire. This is based on records collected systematically from 5 x 5 km grid squares since 1982 and data from earlier studies. 434 taxa have been recorded since exploration began in about 1660, of these 55 have not been refound since 1980 or earlier. The maps reveal strong distribution patterns in response to calcium carbonate content of the soil, variations in precipitation, the presence of ancient woodland and the influence of atmospheric pollutants. A comparison of the contemporary flora with that revealed by earlier studies reveals a marked decline in frequency of bryophytes of earth-capped walls, heathland, calcareous grassland, mire and fen, arable field taxa and epiphytes. At least seven liverworts and 50 mosses appear to have increased in frequency. These changes can be attributed to the loss and damage of heathland by scrub invasion and burning, agricultural improvement of natural grassland, cessation of coppicing, early ploughing and fertilizing of arable land, acidification and weathering of substrata by pollutants, loss of mature elms through Dutch Elm Disease and invasions by aliens. Atmospheric pollution has caused losses, particularly of epiphytes, but with falling SO2 pollution in the east some taxa appear to be rapidly recolonizing lost territory.