EFFECTS OF INVASION OF AN ASPEN FOREST (CANADA) BY DENDROBAENA-OCTAEDRA (LUMBRICIDAE) ON PLANT-GROWTH

Effects of invasion of an aspen forest in the Canadian Rocky Mountains by the earthworm Dendrobaena octaedra (Savigny) on nutrient mineralization, soil microflora, and plant growth were investigated during the growth period of 1992. Experimental chambers with reconstructed forest floor were placed in the held and destructively sampled after 7 and 14 wk. D. octaedra enhanced the shoot biomass of the grass Agropyron trachycaulum (Link) Malte (Poaceae) and increased the shoot-to-root ratio during early plant growth. Microbial biomass, basal respiration and respiratory quotient qCO(2) in L/F layer material were reduced by D. octaedra but increased in the H layer. The nutrient (NH4+, NO3-, PO43-) content in soil was also affected by D. octaedra but the effects were small. Effects of the earthworms on soil nutrient content were masked by the great variation in the data and by leaching of nutrients from experimental chambers.