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Titel |
Modelling in situ enzyme potential of soils: a tool to predict soil respiration from agricultural fields |
VerfasserIn |
Rana Shahbaz Ali, Christian Poll, Scott Demyan, Yvonne Nkwain Funkuin, Joachim Ingwersen, Hans-Dieter Wizemann, Ellen Kandeler |
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 |
250094711
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Publikation (Nr.) |
EGU/EGU2014-10139.pdf |
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Zusammenfassung |
The fate of soil organic carbon (SOC) is one of the largest uncertainties in predicting future
climate and terrestrial ecosystem functions. Extra-cellular enzymes, produced by
microorganisms, perform the very first step in SOC degradation and serve as key components
in global carbon cycling. Very little information is available about the seasonal variation in
the temperature sensitivity of soil enzymes. Here we aim to model in situ enzyme
potentials involved in the degradation of either labile or recalcitrant organic compounds
to understand the temporal variability of degradation processes. To identify the
similarities in seasonal patterns of soil respiration and in situ enzyme potentials,
we compared the modelled in situ enzyme activities with weekly measured soil
CO2 emissions. Arable soil samples from two different treatments (4 years fallow
and currently vegetated plots; treatments represent range of carbon input into soil)
were collected every month from April, 2012 to April, 2013, from two different
study regions (Kraichgau and Swabian Alb) in Southwest Germany. The vegetation
plots were under crop rotation in both study areas. We measured activities of three
enzymes including β-glucosidase, xylanase and phenoloxidase at five different
temperatures. We also measured soil microbial biomass in form of microbial carbon
(Cmic). Land-use and area had significant effects (P < 0.001) on the microbial
biomass; fallow plots having less Cmic than vegetation plots. Potential activities of
β-glucosidase (P < 0.001) and xylanase (P < 0.01) were significantly higher in
the vegetation plots of the Swabian Alb region than in the Kraichgau region. In
both study areas, enzyme activities were higher during vegetation period and lower
during winter which points to the importance of carbon input and/or temperature and
soil moisture. We calculated the temperature sensitivity (Q10) of enzyme activities
based on laboratory measurements of enzyme activities at a range of incubation
temperatures. Q10 of β-glucosidase activity changed significantly across the year (Q10
values ranges from 1.5 to 2.0 in Kraichgau and 1.6 to 2.1 in Swabian Alb), while
for xylanase activity, no significant effects were found (Q10 values ranges from
1.2 to 3.0 in Kraichgau and 1.3 to 3.3 in Swabian Alb) in both study regions. By
using laboratory based enzyme activities, calculated Q10 values, and daily soil
temperature data, we modelled in situ enzyme potentials in soils for labile and
recalcitrant carbon pools for both study regions. We observed an increase in modelled in
situ enzyme activities during the summer period and a substantial decrease during
winter indicating temperature as a strong controlling factor. A significant higher
positive correlation of soil surface CO2 flux with modelled in situ β-glucosidase
activity was found in both study regions compared to modelled in situ xylanase
activity.
These results demonstrate that (1) Q10 values are site and season specific and should be
added into carbon models and (2) the indication of the relevance of greater contribution of
labile carbon pool to soil CO2 emissions. |
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