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Harvard Forest Symposium Abstract 2018

• Title: Environmental controls of daytime leaf carbon exchange: Implications for estimates of ecosystem fluxes in a deciduous forest
• Primary Author: Mary Heskel (Marine Biological Laboratory)
• Additional Authors: Jim Tang (Marine Biological Laboratory)
• Abstract:

  Leaf-level photosynthesis and respiration are sensitive to short- and long-term changed in temperature, and how these processes respond to phenological and seasonal transitions and daily temperature variation dictate how carbon is first assimilated and released in terrestrial ecosystems. We examined the short-term temperature response of daytime leaf carbon exchange at Harvard Forest across growing season, with the specific objective to quantify the light inhibition of dark respiration and photorespiration in leaves and use this to better inform daytime carbon assimilation and efflux estimates at the canopy scale. Dark and light respiration increased with measurement temperature and varied seasonally in a proportional manner, with the level of inhibition remaining relatively constant through the growing season. Higher rates of mitochondrial respiration and photorespiration at warmer temperatures drove a lower carbon use efficiency. Using temperature, light, and canopy leaf area index values to drive models, we estimate partitioned ecosystem fluxes and re-calculate gross primary production under multiple scenarios that include and exclude the impact of light inhibition, thermal acclimation, and seasonal variation in physiology. Quantifying the contribution of these ‘small fluxes’ to ecosystem carbon exchange in forests provides a nuanced approach for integrating physiology into regional model estimates derived from eddy covariance and remote-sensing methods.

• Research Category: Physiological Ecology, Population Dynamics, and Species Interactions
  Forest-Atmosphere Exchange