Allium ursinum litter triggering decomposition on a beech forest floor - the effect of earthworms

A laboratory experiment was carried on the microbial use of Allium ursinum L. litter in a calcareous beech (Fagus sylvatica L.) forest soil. Non-label ed and C-14 labeled litter of A. ursinum and beech was applied to different iate between C originating from the two litter types. The earthworm species Lumbricus rubellus was added to part of the microcosms. Cumulative C-14 mi neralisation and microbial C-14 incorporation served as parameters for the C turnover of the microflora. The experiment lasted for 34 days. About 1.6 % of beech litter C and 47 % of A. ursinum C had been mineralized in the non-earthworm treatments at the end of the experiment. Litter of A. ursinum may thus partly compensate a potential C deficit of the decomposer community in early summer. The high metabolic quotient (q(14)CO(2)) indica tes that decomposition of A. ursinum litter may significantly increase the nutrient availability in the soil of the Gottinger Wald area in early summe r This effect could even be amplified by the fact that A. ursinum litter al so increased the metabolic quotient of the microflora colonizing beech litt er. L. rubellus used C from both litter types for biomass production. Strong in corporation of A. ursinum C seems to be due rather to better usability than to selective ingestion. Increased C-14 mineralisation and decreased microb ial C-14 incorporation indicates that small and fast growing microorganisms are favored in earthworm worked soil. This was not fundamentally altered b y litter quality. Depression of C-14(mic) by L. rubellus to:almost identica l values in all litter treatments indicates that microbial growth was limit ed. The fact that A. ursinum litter did not modify the effect of L. rubellu s on the microbial use of beech litter indicates that C and N availability did not limit the microflora.