Ref ID : 6910
Alexei V. Tiunov and Stefan Scheu; Microbial respiration, biomass, biovolume and nutrient status in burrow walls of Lumbricus terrestris L. (Lumbricidae). Soil Biol.Biochem. 31:2039-2048, 1999
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Chemical characteristics and microbial activity were studied in burrow walls of the anecic earthworm species Lumbricus terrestris and in control soil of a lime (Tilia cordata), oak (Quercus robur) and beech (Fagus sylvatica) forest. Samples were taken in June and October at distances of 0-4 (drilosphere), 8-12 and 50-60 (control soil) mm from earthworm burrows. The following variables were measured: organic C, total N, moisture, pH, basal respiration, microbial biomass (SIR method), fungal and bacterial volume (epifluorescence microscopy) and nutrient (C, N, and P) limitation of microbial growth. Oganic C and total N contents increased in the burrow walls by factors of 1.8-3.5 and 1.3-2.2, respectively, compared to the control soil. The moisture content and pH (up to 1.2 units) was higher. Basal respiration, microbial biomass and bacterial volume in the drilosphere exceeded those in control soil significantly by factors of 3.7-9.1, 2.3-4.7 and 2.1-5.4, respectively. Changes in fungal volume with vicinity to burrows differed between forest sites. Fungal volume was increased significantly by factors of 1.9-3.4 in the earthworm burrow walls in the oak and beech forest, but was similar to that in control soil in the lime forest. Microbial growth in the control soil was limited by N in the oak forest and by N and P in the lime and beech forest. The nutrient status of the microflora changed little in vicinity to burrows. However, microbial N and P demand in earthworm burrow walls exceeded that in soil. The specific respiration (qO2) was increased and the growth response to nutrient additions was faster in the burrow walls suggesting that the microbial community in the burrow walls contains a larger fraction of metabolically-active microorganisms, adapted to continuous resource additions by earthworm faeces and mucus. Enrichment in organic matter, but also other mechanisms, particularly the activity of microbivorous soil animals, are presumably responsible for the formation of a specific microbial community in earthworm burrow walls. It is concluded that L. terrestris burrow walls are stable microhabitats which sustain a large and active microbial community and are likely to play an important role in the soil system by regulating microbial-mediated chemical processes.