Mechanisms of real and apparent priming effects and their dependence on soil microbial biomass and community structure: critical review |
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Authors: | Е Blagodatskaya Y Kuzyakov |
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Institution: | (1) Department of Agroecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany;(2) Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, 142290 Pushchino, Russia |
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Abstract: | The number of studies on priming effects (PE) in soil has strongly increased during the last years. The information regarding
real versus apparent PE as well as their mechanisms remains controversial. Based on a meta-analysis of studies published since
1980, we evaluated the intensity, direction, and the reality of PE in dependence on the amount and quality of added primers,
the microbial biomass and community structure, enzyme activities, soil pH, and aggregate size. The meta-analysis allowed revealing
quantitative relationships between the amounts of added substrates as related to microbial biomass C and induced PE. Additions
of easily available organic C up to 15% of microbial biomass C induce a linear increase of extra CO2. When the added amount of easily available organic C is higher than 50% of the microbial biomass C, an exponential decrease
of the PE or even a switch to negative values is often observed. A new approach based on the assessment of changes in the
production of extracellular enzymes is suggested to distinguish real and apparent PE. To distinguish real and apparent PE,
we discuss approaches based on the C budget. The importance of fungi for long-term changes of SOM decomposition is underlined.
Priming effects can be linked with microbial community structure only considering changes in functional diversity. We conclude
that the PE involves not only one mechanism but a succession of processes partly connected with succession of microbial community
and functions. An overview of the dynamics and intensity of these processes as related to microbial biomass changes and C
and N availability is presented. |
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Keywords: | Priming effect Soil microbial community Isotopic methods Soil respiration Carbon sequestration Carbon and nitrogen turnover Soil organic matter Triggering effect Glucose |
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