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| Titel |
Enhanced utilization of labile substrate in the soil in absence of plant C input through roots and ectomycorrhizal fungi |
| VerfasserIn |
N. R. Voke, J.-A. Subke, R. Nair, P. Ineson |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023854
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| Zusammenfassung |
| Soils form a significant store of carbon (C) in terrestrial ecosystems, and hold the potential to
mitigate or enforce global environmental change. The direction of such climate
driven feedbacks depends on the way in which processes of C sequestration and
release from soils are affected by changes in environmental conditions. There is an
increasing realization that complex interactions between plants and soil organisms are
crucial for the stability of soil organic matter (SOM). However, we still lack a good
understanding of the nature of this interdependence and its likely environmental
responses. The aim of this study is to investigate how 13C labeled glucose is utilized
in the presence or absence of inputs from plants through roots. Specifically we
aim to investigate the importance of EM fungi in the control of carbon cycling in
forest ecosystems and the influence of EM fungi on the activity of rhizospheric soil
microorganisms.
We installed four replicates each of three different collar treatments in a 18-year old
Lodgepole pine (Pinus contorta) stand near York (NE England). These consisted of deep soil
collars with four windows just below surface level covered either by 1μm mesh in order to
exclude both roots and hyphae (treatment S) or 41μm mesh to exclude just roots (treatment
M). The third set of collars was inserted to a shallow depth of c. 1.5 cm, thus allowing
natural access by roots and hyphae (treatment R). Soil moisture levels were controlled
through the exclusion of natural throughfall using PVC shields above the collars. Throughfall
collectors were positioned in the experimental plot and an average amount of throughfall was
added to each of the soil cores weekly. Six months following collar insertion, we
applied 13C-labelled glucose to all collars. CO2 flux (RS) from all collars as well as
its isotopic composition was measured continuously using a field-deployed mass
spectrometer, and we estimate microbial utilization of the glucose using the return flux of
13CO2.
The results show a significantly higher RS and δ13C from collars excluding any plant
derived C input. Respiration of glucose derived CO2 was of similar magnitude for the other
two treatments, but was more sustained in treatment R (i.e. including both roots and
mycorrhizal hyphae). It is likely that the increase in RS observed were from the increased
activity of saprotrophic fungi and other soil microorganisms. EM fungi and associated
bacteria might not be expected to respond in the same way to the introduction of a
simple C substrate since they receive this predominantly from their plant hosts.
Therefore one interpretation of these results is that under normal conditions in this EM
dominated system, saprotrophs are suppressed by the presence of EM fungi. These
results highlight the potential for plants, through their C inputs to influence the
level of decomposition taking place in terrestrial ecosystems, and highlight the
importance of EM fungi and competition between soil microorganisms in this process. |
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