STRATOSPHERIC OZONE REDUCTION AND ECOSYSTEM PROCESSES - ENHANCED UV-BRADIATION AFFECTS CHEMICAL-QUALITY AND DECOMPOSITION OF LEAVES OF THEDUNE GRASSLAND SPECIES CALAMAGROSTIS-EPIGEIOS

This study reports changes in the plant's chemical composition and the decomposition of this plant material under enhanced solar UV-B radiat ion. Calamagrostis epigeios, a dominant grass species in the dune gras sland in The Netherlands, was grown outdoor on an experimental field u nder ambient and enhanced solar UV-B (5 and 7.5 kJ m(-2) day(-1) UV-B- BE, respectively), corresponding to about 15% stratospheric ozone depl etion. After one growing season aerial plant parts were harvested. The decomposition of this harvested leaf material was studied in a dune g rassland and on the above mentioned experimental field under ambient ( 5 kJ m(-2) day(-1) UV-B-BE) and enhanced (7.5 kJ m(-2) day(-1) UV-B-BE ) radiation, using litter bags. The chemical quality of the leaves gro wn under enhanced solar UV-B changed. There was an increase in the lea f content of lignin, while no significant changes occurred for the con tent of alpha-cellulose, hemicellulose and tannins under enhanced UV-B . In the field, the rate of decomposition of leaf material grown under enhanced UV-B (with an increased content of lignin) was reduced. The content of lignin of the decomposing leaf material increased, but less under exposure to enhanced UV-B. The latter may be explained by photo degradation of the lignin. The consequences of enhanced UV-B radiation for carbon fluxes in the dune grassland ecosystem are discussed.