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| Titel |
Three-source-partitioning of soil carbon pools and fluxes and priming effects induced by carbohydrates of different availability |
| VerfasserIn |
E. Blagodatskaya, N. Khomyakov, O. Myachina, S. Blagodatsky, Y. Kuzyakov |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065624
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| Zusammenfassung |
| Soil organic matter (SOM) is not uniform and includes: 1) fresh input of plant-derived
organics, i.e. root exudates and rhizodeposits, 2) partially decomposed plant residues and 3)
old humus material. The partitioning of these three carbon sources in soil C pools (microbial
biomass and dissolved organic matter) and quantification of their contributions in soil CO2
?uxes is a current challenge in soil science aiming to reveal the C pathways and
drivers in terrestrial ecosystems. We applied uniformly labeled 14C-cellulose and
14C-glucose (as low and easily available substrates, respectively) in Ap of loamy
Haplic Luvisol developed under C3 vegetation. Miscanthus x giganteus (Greef et
Deu) – a perennial C4 plant – was grown for 12 years before the experiment with
glucose/cellulose addition. Natural differences in the abundance of 13C between C4
and C3 plants were used to distinguish between old SOC (> 12 years) and recent
Miscanthus-derived C (< 12 years). This enabled us to estimate mechanisms and sources
of priming effects (PE) during decomposition of applied substrates with varying
availability. The real and apparent priming effects were distinguished by partitioning of
microbial C for substrate-C and SOM-derived C. Microbial specific growth rates and
activity of hydrolytic enzymes were determined to reveal the mechanisms of real
PEs.
Both short-term apparent and long-term real PEs were induces by glucose, while
the cellulose input caused only real PE. Remarkably, the shift to the domination
of slow-growing microorganisms was observed during real PEs independently of
substrate quality. This is the first direct confirmation of the hypothesized presumable
contribution of K-strategists to real priming. 2.5-3 times increase in beta-glucosidase and
phosphatase activity coupled with real PE in soil treated with glucose indicated that
strong limitation and microbial starvation after glucose consumption caused the PE.
Contrary to that the 75% increase in cellobiohydrolase activity (enzyme decomposing
cellulose) indicated the co-metabolism as a possible mechanism of PE induced by
cellulose.
We conclude that 3-source-partitioning based on a combination of 14C labeling and
estimation of 13C natural abundance is a very useful tool in clearly separating sources and
evaluating mechanisms of priming effects. |
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