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| Titel |
Carbon dioxide emissions of soils under pure and mixed stands of beech and spruce, affected by decomposing foliage litter mixtures |
| VerfasserIn |
Torsten W. Berger, Erich Inselsbacher, Sophie Zechmeister-Boltenstern |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036872
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| Zusammenfassung |
| Soil respiration is the largest terrestrial source of CO2 to the atmosphere. In forests, roughly
half of the soil respiration is autotrophic (mainly root respiration) while the remainder is
heterotrophic, originating from decomposition of soil organic matter. Decomposition is an
important process for cycling of nutrients in forest ecosystems. Hence, tree species
induced changes may have a great impact on atmospheric CO2 concentrations.
Since studies on the combined effects of beech-spruce mixtures are very rare, we
firstly measured CO2 emission rates in three adjacent stands of pure spruce (Picea
abies), mixed spruce-beech and pure beech (Fagus sylvatica) on three base-rich
sites (Flysch) and three base-poor sites (Molasse; yielding a total of 18 stands)
during two summer periods using the closed chamber method. CO2 emissions were
higher on the well aerated sandy soils on Molasse than on the clayey soils on Flysch,
characterized by frequent water logging. Mean CO2 effluxes increased from spruce (41)
over the mixed (55) to the beech (59) stands on Molasse, while tree species effects
were lower on Flysch (30-35, mixed > beech = spruce; all data in mg CO2-C m-2
h-1). Secondly, we studied decomposition after fourfold litter manipulations at
the 6 mixed species stands: the Oi- and Oe horizons were removed and replaced
by additions of beech -, spruce - and mixed litter of the adjacent pure stands of
known chemical quality and one zero addition (blank) in open rings (20 cm inner
diameter), which were covered with meshes to exclude fresh litter fall. Mass loss
within two years amounted to 61-68% on Flysch and 36-44% on Molasse, indicating
non-additive mixed species effects (mixed litter showed highest mass loss). However, base
cation release showed a linear response, increasing from the spruce - over the mixed
- to the beech litter. The differences in N release (immobilization) resulted in a
characteristic converging trend in C/N ratios for all litter compositions on both bedrocks
during decomposition. In the summers 2006 and 2007 we measured CO2 efflux from
these manipulated areas (a closed chamber fits exactly over such a ring) as field
indicator of the microbial activity. Net fluxes (subtracting the so-called blank values)
are considered an indicator of litter induced changes only and increased on both
bedrocks from the spruce - over the mixed - to the beech litter. According to these
measurements, decomposing litter contributed between 22-32% (Flysch) and 11-28%
(Molasse) to total soil respiration, strengthening its role within the global carbon cycle. |
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