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TitleModelling CO 2 and energy exchanges in a northern semiarid grassland using the carbon- and nitrogen-coupled Canadian Land Surface Scheme (C-CLASS)
AuthorZhang, Y; Grant, R F; Flanagan, L B; Wang, SORCID logo; Verseghy, D L
SourceEcological Modelling vol. 181, no. 4, 2005 p. 591-614,
Alt SeriesNatural Resources Canada, Contribution Series 20181777
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
Subjectsgeophysics; remote sensing
ProgramCanada Centre for Remote Sensing Divsion
AbstractThe development of carbon (C) and nitrogen (N) simulations is one of the ongoing efforts in the land surface schemes of climate models. The C- and N-coupled Canadian Land Surface Scheme (C-CLASS) was recently modified to better represent grassland ecosystems. Improvements include revised plant growth and senescence calculations that are driven by the plant C balance between fixation and respiration, and leaf-out and leaf-fall schemes that are regulated by the seasonal dynamics of C and N reserves. These revisions were developed to better simulate the stress-related senescence and regrowth of perennials. The model was tested with observations of surface carbon and energy fluxes, soil temperature and moisture, and plant growth during 3 years of declining precipitation at a northern semiarid grassland near Lethbridge, Alberta, Canada. The R 2 and standard deviations between the simulated and observed half-hourly fluxes were 0.95 and 22.5 W m -2 for net radiation, 0.82 and 42.1 W m -2 for sensible heat, 0.66 and 29.2 W m -2 for latent heat, and 0.63 and 0.95 ?mol C m -2 s -1 for net CO 2 exchange. The model and observations both showed a strong impact of declining precipitation on annual carbon budgets in this semi-arid grassland. In a wet year (1998, precipitation = 482 mm), the ecosystem acted as a strong C sink (92 g C m -2 modelled and 109 g C m -2 measured from June 20th to December 31st). In a near-normal year (1999, precipitation = 341 mm), a smaller C sink was indicated (24 g C m -2 modelled and 21 g C m -2 measured). In a dry year (2000, precipitation = 276 mm), the ecosystem acted as a small C source (-18 g C m -2 modelled and -17 g C m -2 measured)

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