Importance of food quality on selected enzyme activities in earthworm casts (Dendrobaena octaedra, Lumbricidae)

Dehydrogenase (DHA), acid (SPA) and alkaline (APA) phosphomonesterase activities in the casts of Dendrobaena octaedra were analysed while the animals were offered one of six different food sources. The food consisted of air dried leaves of dandelion, lupin, rye, alder, beech and larch. The food consumption rate of the earthworms lay between 11.1 mg (dandelion) and 0.3 mg d·w· g−1 f·w· d−1 (larch) while the cast production varied between 252 mg (dandelion) and 835 mg d·w· g−1 f·w· d−1 (beech). A deterioration of the food quality caused a reduction of the food consumption rate, but simultaneously the mean turn-over rate of soil aggregates was enhanced. The enzyme activities were influenced by the food which affected the specific nutrient state of the casts. DHA, SPA and APA were significantly correlated with the organic C and the total N content of the casts. Interenzymatic correlations illustrated the applicability of the three enzyme activities as useful indicators of the influence of earthworms and their food on soil quality.