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| Titel |
Sub-grid scale representation of vegetation in global land surface schemes: implications for estimation of the terrestrial carbon sink |
| VerfasserIn |
J. R. Melton, V. K. Arora |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 4 ; Nr. 11, no. 4 (2014-02-21), S.1021-1036 |
| Datensatznummer |
250117239
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| Publikation (Nr.) |
 copernicus.org/bg-11-1021-2014.pdf |
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| Zusammenfassung |
| Terrestrial ecosystem models commonly represent vegetation in terms of
plant functional types (PFTs) and use their vegetation attributes in
calculations of the energy and water balance as well as to investigate the
terrestrial carbon cycle. Sub-grid scale variability of PFTs in these models
is represented using different approaches with the "composite" and
"mosaic" approaches being the two end-members.
The impact of these two approaches on the global carbon
balance has been investigated with the Canadian Terrestrial Ecosystem
Model (CTEM v 1.2) coupled to the Canadian Land Surface Scheme (CLASS
v 3.6). In the composite (single-tile) approach, the vegetation
attributes of different PFTs present in a grid cell are aggregated and
used in calculations to determine the resulting physical environmental
conditions (soil moisture, soil temperature, etc.) that are common to
all PFTs. In the mosaic (multi-tile) approach, energy and water
balance calculations are performed separately for each PFT tile and
each tile's physical land surface environmental conditions evolve
independently. Pre-industrial equilibrium CLASS-CTEM simulations yield
global totals of vegetation biomass, net primary productivity, and
soil carbon that compare reasonably well with observation-based
estimates and differ by less than 5% between the mosaic and
composite configurations. However, on a regional scale the two
approaches can differ by > 30%, especially in areas with
high heterogeneity in land cover. Simulations over the historical
period (1959–2005) show different responses to evolving climate and
carbon dioxide concentrations from the two approaches. The cumulative
global terrestrial carbon sink estimated over the 1959–2005 period
(excluding land use change (LUC) effects) differs by around
5% between the two approaches (96.3 and 101.3 Pg, for the
mosaic and composite approaches, respectively) and compares well with
the observation-based estimate of 82.2 ± 35 Pg C over the same
period. Inclusion of LUC causes the estimates of the terrestrial C
sink to differ by 15.2 Pg C (16%) with values of 95.1 and
79.9 Pg C for the mosaic and composite approaches,
respectively. Spatial differences in simulated vegetation and soil
carbon and the manner in which terrestrial carbon balance evolves in
response to LUC, in the two approaches, yields a substantially
different estimate of the global land carbon sink. These results
demonstrate that the spatial representation of vegetation has an
important impact on the model response to changing climate,
atmospheric CO2 concentrations, and land cover. |
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