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| Titel |
Climate sensitivity and macronutrient regulation of peat decomposition |
| VerfasserIn |
Rachel Marshall, Nick Ostle, Niall McNamara, Elizabeth Baggs |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072277
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| Zusammenfassung |
| Organic soils act as vital global carbon stores maintained in northern latitudes by climate and
nutrient limited rates of organic matter decomposition. Peatland decomposition rates are
sensitive to climate change, however predicting the magnitude of the microbial respiratory
response is complex due to unknown interactions between climate and substrate quality. The
nutrient status of peatlands varies widely from mineral rich fens to nutrient poor
ombrotrophic bogs, which have the potential to respond differently to climate driven changes
in temperature and carbon (C) inputs. In this work we examine the links between
peatland macronutrient C, phosphorus (P) and nitrogen (N) stoichiometry, microbial
community structure and the microbial response to direct and indirect effects of climate
change.
Using total soil C:N and C:P ratios to define nutrient gradients in organic soils from
Svalbard and Finland we investigated the interaction between the microbial response to
temperature and nutrient limitation of decomposition. In organic rich soils from Svalbard we
found there was a significant relationship between increasing temperature sensitivity of
respiration and decreasing total soil P concentrations. Further investigation of the potential
direct link between P limitation of decomposition and increased temperature sensitivity
along a minerotrophic-ombroptrophic gradient in Finland was performed using
multi-factorial P limitation assays. These showed that despite varying degrees of P
limitation across four peatland soils there was no relationship between P limitation and
increased temperature sensitivity of soil respiration. Throughout this study we found
consistently high temperature sensitivity of decomposition in organic rich soils with
Q10 values ranging between 2 to 4.5, indicating potentially higher vulnerability of
these C stores to warming than is currently predicted using a globally invariant
Q10.
Following on from this we examined the interaction between peatland nutrient status and
the potential for labile C substrates to stimulate (prime) decomposition of the peat organic
matter. Using 13C labelled glucose and hemicellulose compounds we observed significant
differences in the amount and rate of microbial substrate use between peats with differing
nutrient status. Nutrient addition experiments were used with labelled C substrates to
investigate the role of N and P limitation in enhancing or restricting priming effects. This is
one of the first studies to use 13C substrates to examine potential priming effects in peat
soil and it provides an insight into the importance of priming mechanisms in peat
decomposition.
This work explicitly links soil microbial responses to temperature and nutrient
manipulations with microbial community structure allowing us to observe how microbial
communities mediate soil C losses in peat soils. Disentangling the complex interactions
between soil microbial community, C and nutrient limitation of decomposition is essential for
predicting the vulnerability of different peatland ecosystems to climate driven changes. |
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