COGNETTIA SPHAGNETORUM (ENCHYTRAEIDAE) AND NUTRIENT CYCLING IN ORGANIC SOILS - A MICROCOSM EXPERIMENT

A microcosm experiment was carried out to investigate the role of ench ytraeids in nitrogen and phosphorus mineralisation in an organic grass land soil. Soil cores were taken from a cambic stagnohumic gley with a ssociated vegetation in the Moor House National Nature Reserve (UK), d efaunated, separated into 3 cm layers and inoculated with Cognettia sp hagnetorum (Vejdovsky) in microcosms, maintained at 15 degrees C in th e laboratory. The leaching of dissolved organic nitrogen (DON), ammoni um and phosphorus (total, organic and soluble reactive phosphorus) was monitored over 8 weeks, and found to be significantly greater in the presence of C. sphagnetorum; this effect varied with soil depth, highe st increases being found in the 0-3 and 3-6 cm soil layers. The pH in the leachates was also increased in the presence of Cognettia. The imp acts of seasonal vertical distribution of enchytraeids on nutrient cyc ling are discussed, together with the implications of climate change i n these systems. (C) 1998 Elsevier Science B.V.