PARENT SESSION
Poster Session #12: Modeling.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Accurate assessment of respiration acclimation to temperature is critical for carbon balance modeling.
Wythers, Kirk1, Tjoelker, Mark2, Reich, Peter1, Bolstad, Paul1, Lee, Tali1, 1 2
ABSTRACT- The carbon balance of plants and ecosystems depends greatly upon the effects of temperature on respiratory carbon loss. Computer models often simulate a carbon balance using baseline respiration rates and a fixed exponential relationship (Q10) between respiration rate and temperature. However, respiration rates are known to acclimate to temperature changes. We assessed such changes for several woody species using physiological experiments and observations. We used a combination of field data and model simulations to explore the implications of respiration acclimation to temperature in modeled carbon balance estimations. We used physiological data to modify the respiration algorithms of a temperate forest canopy model (PnET) to allow both Q10 and baseline foliage respiration to adjust to temperature changes. When we allowed both Q10 and base foliar respiration to adjust dynamically, model output indicated a 50 percent decrease (at 20 degrees C) in night time respiration relative to model runs with fixed Q10 and base foliage respiration parameters. The effects of acclimation varied substantially within years and among sites when tested on a broad gradient. These results suggest that models which do not modify their respiration estimates to reflect temperature acclimation may overestimate respiratory carbon loss.
KEY WORDS: modeling, respiration, acclimation, temperature