Scaling foliar respiration to the stand level throughout the growing season in a Quercus rubra forest

Stand-level, canopy foliar carbon loss (R,an) was modeled for a virtual Quercus rubra L. monoculture at two sites differing in soil water availability in a northeastern deciduous forest (USA) throughout the 2003 growing season. Previously reported foliar respiratory temperature responses of Q. rubra were used to parameterize a full distributed physiology model that estimates R-can by integrating the effects of season, site and canopy position, and represents the best estimation of R-can. Model sensitivity to five simplified parameterization scenarios was tested, and a reasonable procedure of simplification was established. Neglecting effects of season, site or canopy position on respiration causes considerable relative error in R-can estimation. By contrast, assuming a constant E-0 (a temperature response variable of the respiration model), or a constant night temperature (mean nighttime temperature) caused only a small relative error (< 10%) compared with the full model. From June 8 to October 28, 2003, modeled R-can of the virtual Q. rubra monoculture was, on average, 45.3 mmol CO2 m(-2) night(-1) on a ground-area basis (or 334 mmol CO2 kg(-1) night(-1) on a biomass basis) and 101 mmol CO2 m(-2) night(-1) (or 361 mmol CO2 kg(-1) night(-1)) at the drier site and the more mesic site, respectively. To model R,, of Q. rubra (or other Quercus species with similar respiratory properties), variations in the base respiration rate across season, site and canopy position need to be fully accounted for, but E0 may be assumed constant, Modeling R-can at the mean nighttime temperature would not strongly affect estimated canopy carbon loss.