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| Titel |
Evaluation and improvement of the Community Land Model (CLM4) in Oregon forests |
| VerfasserIn |
T. W. Hudiburg, B. E. Law, P. E. Thornton |
| 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 ; 10, no. 1 ; Nr. 10, no. 1 (2013-01-24), S.453-470 |
| Datensatznummer |
250017482
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| Publikation (Nr.) |
 copernicus.org/bg-10-453-2013.pdf |
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| Zusammenfassung |
| Ecosystem process models are important tools for determining the interactive
effects of global change and disturbance on forest carbon dynamics. Here we
evaluated and improved terrestrial carbon cycling simulated by the
Community Land Model (CLM4), the land model portion of the Community Earth System Model
(CESM1.0.4). Our analysis was conducted primarily in Oregon forests using
FLUXNET and forest inventory data for the period 2001–2006. We go beyond
prior modeling studies in the region by incorporating regional variation in
physiological parameters from >100 independent field sites in
the region. We also compare spatial patterns of simulated forest carbon
stocks and net primary production (NPP) at 15 km resolution using data
collected from federal forest inventory plots (FIA) from >3000
plots in the study region. Finally, we evaluate simulated gross primary
production (GPP) with FLUXNET eddy covariance tower data at wet and dry
sites in the region. We improved model estimates by making modifications to
CLM4 to allow physiological parameters (e.g., foliage carbon to nitrogen
ratios and specific leaf area), mortality rate, biological nitrogen
fixation, and wood allocation to vary spatially by plant functional type
(PFT) within an ecoregion based on field plot data in the region. Prior to
modifications, default parameters resulted in underestimation of stem
biomass in all forested ecoregions except the Blue Mountains and annual NPP
was both over- and underestimated. After modifications, model estimates of
mean NPP fell within the observed range of uncertainty in all ecoregions
(two-sided P value = 0.8), and the underestimation of stem biomass was
reduced. This was an improvement from the default configuration by 50%
for stem biomass and 30% for NPP. At the tower sites, modeled monthly GPP
fell within the observed range of uncertainty at both sites for the majority
of the year, however summer GPP was underestimated at the Metolius semi-arid
pine site and spring GPP was overestimated at the Campbell River mesic
Douglas-fir site, indicating GPP may be an area for further improvement. The
low bias in summer maximum GPP at the semi-arid site could be due to
seasonal response of Vcmax to temperature and precipitation while
overestimated spring values at the mesic site could be due to response of
Vcmax to temperature and day length. |
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