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| Titel |
Carbon flux from plants to soil microbes is highly sensitive to nitrogen addition and biochar amendment |
| VerfasserIn |
C. Kaiser, Z. M. Solaiman, M. R. Kilburn, P. L. Clode, L. Fuchslueger, M. Koranda, D. V. Murphy |
| 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 |
250068949
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| Zusammenfassung |
| The release of carbon through plant roots to the soil has been recognized as a governing
factor for soil microbial community composition and decomposition processes, constituting
an important control for ecosystem biogeochemical cycles. Moreover, there is increasing
awareness that the flux of recently assimilated carbon from plants to the soil may regulate
ecosystem response to environmental change, as the rate of the plant-soil carbon transfer will
likely be affected by increased plant C assimilation caused by increasing atmospheric CO2
levels. What has received less attention so far is how sensitive the plant-soil C transfer would
be to possible regulations coming from belowground, such as soil N addition or
microbial community changes resulting from anthropogenic inputs such as biochar
amendments.
In this study we investigated the size, rate and sensitivity of the transfer of recently
assimilated plant C through the root-soil-mycorrhiza-microbial continuum. Wheat plants
associated with arbuscular mycorrhizal fungi were grown in split-boxes which were filled
either with soil or a soil-biochar mixture. Each split-box consisted of two compartments
separated by a membrane which was penetrable for mycorrhizal hyphae but not for roots.
Wheat plants were only grown in one compartment while the other compartment
served as an extended soil volume which was only accessible by mycorrhizal hyphae
associated with the plant roots. After plants were grown for four weeks we used a
double-labeling approach with 13C and 15N in order to investigate interactions between
C and N flows in the plant-soil-microorganism system. Plants were subjected to
an enriched 13CO2 atmosphere for 8 hours during which 15NH4 was added to a
subset of split-boxes to either the root-containing or the root-free compartment.
Both, 13C and 15N fluxes through the plant-soil continuum were monitored over
24 hours by stable isotope methods (13C phospho-lipid fatty acids by GC-IRMS,
15N/13C in bulk plant material, microbial biomass and dissolved organic matter by
IRMS, 13C and 15N in plant roots cells and intraradical mycorrhizal hyphae by
NanoSims).
Our results show that (1) C assimilated by plants was delivered within 4 hours to the soil
microbial community both via roots and the mycorrhizal network (2) N addition during the
labeling period strongly and rapidly increased the 13C flux of recently assimilated
carbohydrates to the soil microbial biomass (3) the effect of N addition was not as rapid
but was of the same magnitude when N was delivered to the plant exclusively by
mycorrhizal hyphae as compared to taken up by roots (4) soils which had been
amended with biochar (which were characterized by an increased abundance of
mycorrhizal fungi) also showed a significant increase of C flux from plants to the
soil.
We conclude that plant belowground C allocation is highly sensitive to alterations of
microbial community structure and nutritional status in the soil. Moreover, our results
indicate that plants respond rapidly (within hours) to changing soil N availability by altering
the rate of C transported belowground. Our results emphasise the ecological significance of
plant-belowground interactions for ecosystem C cycling. |
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