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| Titel |
Introducing litter quality to the ecosystem model LPJ-GUESS: Effects on short- and long-term soil carbon dynamics |
| VerfasserIn |
Hanspeter Portner, Annett Wolf, Nadine Rühr, Harald Bugmann |
| 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 |
250041316
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| Zusammenfassung |
| Many biogeochemical models have been applied to study the response of the carbon cycle to
changes in climate, whereby the process of carbon uptake (photosynthesis) has usually gained
more attention than the equally important process of carbon release by respiration. The
decomposition of soil organic matter is driven by a combination of factors like soil
temperature, soil moisture and litter quality. We have introduced dependence on litter
substrate quality to heterotrophic soil respiration in the ecosystem model LPJ-GUESS [Smith
et al.(2001)]. We were interested in differences in model projections before and after the
inclusion of the dependency both in respect to short- and long-term soil carbon
dynamics.
The standard implementation of heterotrophic soil respiration in LPJ-GUESS is a simple
carbon three-pool model whose decay rates are dependent on soil temperature and soil
moisture. We have added dependence on litter quality by coupling LPJ-GUESS to the soil
carbon model Yasso07 [Tuomi et al.(2008)]. The Yasso07 model is based on an extensive
number of measurements of litter decomposition of forest soils. Apart from the
dependence on soil temperature and soil moisture, the Yasso07 model uses carbon soil
pools representing different substrate qualities: acid hydrolyzable, water soluble,
ethanol soluble, lignin compounds and humus. Additionally Yasso07 differentiates
between woody and non-woody litter. In contrary to the reference implementation of
LPJ-GUESS, in the new model implementation, the litter now is divided according to its
specific quality and added to the corresponding soil carbon pool. The litter quality
thereby differs between litter source (leaves, roots, stems) and plant functional type
(broadleaved, needleleaved, grass). The two contrasting model implementations were
compared and validated at one specific CarboEuropeIP site (Lägern, Switzerland)
and on a broader scale all over Switzerland. Our focus lay on the soil respiration
for the years 2006 and 2007 [Rühr(2009)] and present soil carbon stocks [Heim
et al.(2009)].
Our Results show, that for short-term soil carbon dynamics, e.g. estimates of
heterotrophic soil respiration on an annual basis, the inclusion of the dependency on litter
quality is not necessary, as the differences are minor only. However, when considering
long-term soil carbon dynamics, e.g. simulated estimates of present soil carbon
content, the dependency on litter quality shows effect, as there are correlations
with specific site factors such as site location and forest type. The inclusion of the
dependence on litter quality therefore may be of importance for the projection of
future soil carbon dynamics, as forest types may well be altered due to climatic
change.
References
[Heim et al.(2009)]   A. Heim, L. Wehrli, W. Eugster, and M.W.I. Schmidt.
Effects of sampling design on the probability to detect soil carbon stock changes
at the swiss CarboEurope site Lägeren. Geoderma, 149(3-4):347–354, 2009.
[Rühr(2009)]   Nadine Katrin Rühr. Soil respiration in a mixed mountain forest
: environmental drivers and partitioning of component fluxes. PhD thesis, ETH,
2009.
[Smith et al.(2001)]   Benjamin Smith, I. Colin Prentice, and Martin T. Sykes.
Representation of vegetation dynamics in the modelling of terrestrial ecosystems:
comparing two contrasting approaches within european climate space. Global
Ecology and Biogeography, 10(6):621–637, 2001.
[Tuomi et al.(2008)]   Mikko Tuomi, Pekka Vanhala, Kristiina Karhu, Hannu
Fritze, and Jari Liski. Heterotrophic soil respiration–Comparison of different
models describing its temperature dependence. Ecological Modelling, 211(1-2):
182–190, 2008. |
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