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| Titel |
Carbon balance of a subarctic meadow under 3 \r{ }C warming -- unravelling respiration |
| VerfasserIn |
Hanna Silvennoinen, Teresa G. Bárcena, Christophe Moni, Marcin Szychowski, Paulina Rajewicz, Mats Höglind, Daniel P. Rasse |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133090
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| Publikation (Nr.) |
 EGU/EGU2016-13667.pdf |
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| Zusammenfassung |
| Boreal and arctic terrestrial ecosystems are central to the climate change debate, as the
warming is expected to be disproportionate as compared to world averages. Northern areas
contain large terrestrial carbon (C) stocks further increasing the interest in the C cycle’s fate
in changing climate. In 2013, we started an ecosystem warming experiment at a meadow in
Eastern Finnmark, NE Norway. The meadow was on a clay soil and its vegetation was
common meadow grasses and clover. Typical local agronomy was applied. The study site
featured ten 4m-wide hexagonal plots, five control and five actively warmed plots in
randomized complete block design. Each of the warmed plots was continuously maintained 3
˚ C above its associated control plot with infrared heaters controlled by canopy thermal
sensors.
In 2014-2015, we measured net ecosystem exchange (NEE) and respiration twice per
week during growth seasons from preinstalled collars of each site with dynamic,
temperature-controlled chambers combined to an infrared analyzer. Despite warming-induced
differences in yield, species composition and root biomass, neither the NEE nor the
respiration responded to the warming, all sites remaining equal sinks for C. Following this
observation, we carried out an additional experiment in 2015 where we aimed at partitioning
the total CO2 flux to microbial and plant respiration as well as at recording the growth season
variation of those parameters in situ. Here, we used an approach based on natural abundances
of 13C. The δ13C signature of both autotrophic plant respiration and heterotrophic
microbial respiration were obtained in targeted incubations (Snell et al. 2014). Then, the
δ13C –signature of the total soil respiration was determined in the field by Keeling
approach with dynamic dark chambers combined to CRDS. Proportions of autotrophic
and heterotrophic components in total soil respiration were then derived based
on 13C mixing model. Incubations were repeated at early, mid and late growth
season and field measurements conducted once per week throughout the growth
season.
We observed differences in the partitioning of the total soil respiration over the three
periods: plant respiration consistently dominated in the control plots (60-100 %), whereas the
warmed plots exhibited a considerably higher share of microbial respiration in the autumn
(70 %; p= 0.03). The share of microbial respiration was also elevated in spring as
compared to the control sites. These results indicate that 1)Partitioning exhibits seasonal
variation 2) Warmer climate may induce a larger proportion of δ13C-enriched C being
decomposed.
At our site, warming had little effect on total respiration but enhanced microbial
respiration at the expense of plant respiration at early and late growth season. Therefore, even
if the local CO2 budgets remained unaffected by the warming climate it may be important to
pay attention to the resilience of soil C on a longer run.
References:
Snell HSK et al. 2014. Rapid Commun. Mass Spectrom. 28: 2341–2351. |
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