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Seasonal variation in the temperature response of leaf respiration in Quercus rubra at the Black Rock Forest
Abstract

Seasonal variation in the temperature response of leaf respiration in Quercus rubra at the Black Rock Forest

K L Griffin and Cheng Yuan Xu
2006 IUFRO Canopy Processes Workshop Book of Abstracts
IUFRO Canopy Processes Workshop: Regional Forest Responses to Environmental Change, 2006 (Massachusetts, United States, 06-Oct-2006–13-Oct-2006)
2006
url
http://people.bu.edu/nathan/iufroabstracts.htmView
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Abstract

Forestry Sciences
Leaf respiratory temperature responses of Quercus rubra were measured throughout the 2003-growing season in a deciduous forest in northeastern USA, in the upper and lower portions of the canopy at two sites with different soil water availability. Consequently, stand-level canopy foliar carbon loss (Rcanopy) was modeled for a virtual Quercus rubra monoculture in these two sites. The base leaf respiration rate (R0, respiration at 10 ºC) of Q. rubra was significantly affected by season, site water availability, canopy height and their interactions. Upper canopy leaves generally had higher R0 than lower canopy leaves. At the drier site, a more significant seasonal pattern in R0 was observed, while at the more mesic site, a stronger canopy position effect was detected. By contrast, the temperature coefficient (E0, the activation energy of respiration as a single reaction) was constant (52.5 ± 5 kJ mol-1). Leaf reducing monose could partially explain the seasonality in respiration (32% - 79%), and leaf nitrogen (Narea) was well correlated to the canopy position effect. Rcanopy of Q. rubra was first estimated by a “full distributed physiology model”, which. integrates the effects of season, site, and canopy position on R0. Sensitivity examination indicates that neglecting the season, site and canopy height effects on leaf respiration resulted in up to a 130% error on the estimation of Rcanopy, but canopy level model parameterizations could be simplified by assuming a constant E0 (error less than 5%). From June 8th to October 28th of 2003, the modeled Rcanopy of the virtual Q. rubra monoculture was 6.3 mol CO2 m-2 ground, and 13.5 mol CO2 m-2 ground, at the drier and the more mesic site respectively. These results suggest that the temporal and spatial heterogeneities of R0 need to be considered in ecosystem models, but it is potentially predictable from well understood leaf properties. Meanwhile, simplifications can be made in Q. rubra by assuming a constant temperature coefficient (E0, e.g. 52.5 kJ mol-1 in this study).

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