Decomposition of 14C glucose in two soils with different amounts of heavy metal contamination |
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| Affiliation: | 1. Department of Agrifood and Environmental Science, University of Florence, Piazzale delle Cascine 18, 50144 Florence, Italy;2. Institute of Microbiology, University of Innsbruck, Technikerstraβe 25d, 6020 Innsbruck, Austria;3. Council for Research and Experimentation in Agriculture, Via Trieste 23, 34170 Gorizia, Italy;4. Department of Bioscence and Territory, University of Molise, Contrada Fonte Lappone snc, 86090 Pesche (IS), Italy;5. Universidade Federal Rural do Rio de Janeiro, Brazil;6. Department of Geography, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland;7. Departamento de Ecología y Biología Animal, Universidad de Vigo, Vigo 36310, Spain;1. Landcare Research, PO Box 69040, Lincoln 7640, New Zealand;2. Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand;1. Department of Agricultural, Food and Environmental Sciences, Università degli Studi di Perugia, Perugia, Italy;2. Department of Agricultural, Food and Environmental Sciences, Università Politecnica delle Marche, Ancona, Italy;3. Department of Biogeochemical Processes, Max Planck Institute for Biogeochemistry, Jena, Germany;4. Department of Agricultural and Food Sciences, Alma Mater Studiorum, Università di Bologna, Bologna, Italy;5. Institute of Ecosystem Study (ISE-CNR), Sesto Fiorentino, FI, Italy |
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| Abstract: | A high metal-containing soil and a low metal-containing soil were supplied with 14C-labelled glucose at two rates, one to provide a constant glucose-to-soil ratio and the other a constant glucose-to-biomass ratio. The aim was to assess the effects of these different ratios on the microbial substrate utilisation efficiency. Glucose was added with or without N to investigate the extraction efficiency of the fumigation-extraction method shortly after substrate addition. The addition of glucose without N resulted in a proportionally larger increase in microbial biomass C than in microbial ninhydrin-reactive N (ENIN) within the first few days after substrate addition, due to N deficiency. The biomass C-to-ENIN ratio remained constant in all soil treatments after glucose addition in combination with N, indicating that the extraction efficiency of the fumigation-extraction method is not affected by the addition of glucose. Lower percentages of glucose added were incorporated into the microbial biomass with an increasing ratio of glucose-to-biomass. The ratio of respired to biomass incorporated 14C increased in all high metal-containing soil treatments markedly above that of the low metal-containing soil from day two of the incubation, markedly overriding the effects on the glucose C-to-biomass C ratio. Our results clearly demonstrated that more substrate was diverted by microorganisms into catabolic at the expense of anabolic processes in a high metal-containing soil. |
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