Comparative growth patterns of the thalloid liverworts Pallavicinia lyellii and Pellia epiphylla at Silwood Park, Southern England

Abstract

Measurements of lobe elongation of the thalloid liverworts Pallavicinia lyellii and Pellia epiphylla were made on shaded streambanks at Silwood Park using a photographic technique. The average cumulative growth of Pallavicinia over 12 months from 1 August 1989 was 8.7 mm compared to 24.7 mm for Pellia. Monthly growth increments of Pallavicinia were positively correlated with average air temperature and accumulated temperatures (day-degrees) in each period. Growth of Pellia was unrelated to temperature. Neither species showed a correlation of growth with rainfall amounts or numbers of wet days, probably because thallus hydration is governed predominantly by soil wetness. Pallavicinia appears to coexist with the more vigorous Pellia by tolerating drier niches than can be endured by Pellia. Persistence of Pallavicinia at this site may be due to the presence of both sexes and frequent colonization of fresh surfaces by spores.