VERTICAL PROFILES OF BIOMASS, LIGHT INTERCEPTING AREA AND LIGHT INTENSITY IN CHALK GRASSLAND MOSSES

Abstract

  Within the framework of a study into competition among chalk grassland bryophytes the light extinction through the canopy was studied in Calliergonella cuspidata, Rhytidiadelphus squarrosus and Ctenidium molluscum on two sampling dates (September and December). By relating the light profile through the canopy to the cumulative light intercepting area (=the moss shoot area index), light extinction coefficients (K) were calculated.

  At both sampling dates the K-values of Ctenidium were higher than those of Calliergonella and Rhytidiadelphus. This corresponds with the more appressed growth-form of Ctenidium.

  For all three species the K-values were higher in September than in December. At the same time shoot areas per unit dry weight were smaller in September than in December. Assuming a more or less constant amount of light-intercepting pigment (chlorophyll) per unit dry weight through the year, this means less light interception per unit shoot area in December, resulting in a lower extinction coefficient.