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| Titel |
Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories |
| VerfasserIn |
Ruirui Chen, Mehmet Senbayram, Sergey Blagodatsky, Klaus Dittert, Xiangui Lin, Evgenia Blagodatskaya, Yakov Kuzyakov |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091101
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| Publikation (Nr.) |
 EGU/EGU2014-5372.pdf |
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| Zusammenfassung |
| The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial
question: how does available N modify the decomposer community and thus affects the
mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect
(PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied
the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding
C4-sucrose or C4-maize straw to C3-soil) in relation to microbial growth kinetics and to the
activities of five hydrolytic enzymes. This encompasses the groups of parameters governing
two mechanisms of priming effects – microbial N mining and stoichiometric decomposition
theories. In sole C treatments, positive PE was accompanied by a decrease in specific
microbial growth rates, confirming a greater contribution of K-strategists to the
decomposition of native SOM. Sucrose addition with N significantly accelerated
mineralization of native SOM, whereas mineral N added with plant residues accelerated
decomposition of plant residues. This supports the microbial mining theory in terms of N
limitation. Sucrose addition with N was accompanied by accelerated microbial
growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased
activities of xylanase and leucine amino peptidase. This indicated an increased
contribution of r-strategists to the PE and to decomposition of cellulose but the decreased
hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed
by exogenous organic C and was controlled by N. This confirms the stoichiometric
decomposition theory. Both K- and r-strategists were beneficial for priming effects,
with an increasing contribution of K-selected species under N limitation. Thus, the
priming phenomenon described in ‘microbial N mining’ theory can be ascribed to
K-strategists. In contrast, ‘stoichiometric decomposition’ theory, that is, accelerated OM
mineralization due to balanced microbial growth, is explained by domination of r-strategists. |
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