DECOMPOSITION IN SALT-MARSH ECOSYSTEMS OF THE SW NETHERLANDS - THE EFFECTS OF BIOTIC AND ABIOTIC FACTORS

Decomposition rates, determined with the litterbag technique in salt marshes of the S.W. Netherlands during the past decade are compared; the biotic and abiotic factors influencing these rates are identified and discussed. Tissue composition is the main variable affecting decay rates of halophytes, particularly variations in lignin content between plant parts and between species. Experiments in which the loss of the tensile strength of cotton strips was used as an index of cellulolytic decay, show that there is a conspicuous variation in decay rates on different sites in a salt marsh. Nonetheless, the locally varying environmental conditions within salt marshes of the S.W. Netherlands have less impact on the variation in decomposition rates of halophyte litter than the chemical make-up of the plant material. Larger fauna elements (> 300-mu-m) may increase decomposition rates, but this effect is only limited and depends on location and litter type. The role of small fauna elements such as nematodes, which occur abundantly in association with halophyte litter, remains largely unknown.