DECOMPOSITION OF CAREX AND SPHAGNUM LITTER IN FENS - EFFECT OF LITTERQUALITY AND INHIBITION BY LIVING TISSUE-HOMOGENATES

Decomposition of fresh litter of Caret diandra, originating from a bas e-rich fen, and Sphagnum fallax, originating from a base-poor fen, was investigated in field experiments with litter bags and laboratory exp eriments with aerobic incubators. The Carex litter decomposed signific antly faster than the Sphagnum litter in all experiments. Further, bot h litter types decomposed faster in the base-rich than in the base-poo r fen. The addition of a small amount of homogenized S. fallax capitul ums to litter of both types in the laboratory experiments significantl y slowed down the rate of weight loss. The addition of homogenized C. diandra leaves did not influence the decay rate. These results suggest that the slow litter decomposition in Sphagnum-dominated mires is due to the chemical composition of the litter itself and the antibiotic e ffect of a substance leaching from living Sphagnum cells. Literature o n the biochemistry of Sphagnales suggests that 'Sphagnum acid', a phen olic compound found in all Sphagna tested, is responsible for these di fferences.