Foliar dark respiration: Scaling gas exchange characteristics and isotopic signals from leaf to canopy and ecosystem level

Foliar respiration contributes up to two thirds of total plant carbon loss and is sensitive to temperature, so it is necessary to understand the response of leaf respiration to environmental factors at multiple scales, given that we intend to predict the long-term effects of climate change. At the community level, species-specific changes in foliar carbon balance can affect the relative competitive ability. At the ecosystem level, a small change in foliar respiration efflux can lead to large effects on the net ecosystem CO2 exchange (NEE) and may alter the carbon sink/source status.; This thesis firstly addresses leaf respiration of Quercus rubra (red oak) and understory shrubs, seasonally in a temperate deciduous forest, and then scales foliar respiration to the canopy level. The base leaf respiration rate (R0, 10°C) of Q. rubra was significantly affected by season, site water availability, canopy height and their interactions, but the activation energy of respiration (E0) was constant. Ignoring the heterogeneity of R0 results in up to a 130% error on the estimation of canopy foliar carbon loss (Rc), but a constant E0 can be assumed in the model. In the understory, leaf respiration was compared between invasive Berberis thunbergii and two native shrubs, Kalmia latifolia and Vaccinium corymbosum. A negative correlation between R0 and E0 was found in all three shrubs. The effect of significant winter warming in southern New York state in the 20th century on Rc is the smallest in the evergreen K. latifolia, which is mainly attributed to the low E0 in this species.; Longer-term, integrated environmental effects on ecosystem respiration can be reflected by stable carbon isotope signals. I surveyed delta 13C of plant respiratory CO2 (delta13C R) in five C3 plants. In all cases, leaf respiratory CO 2 was more 13C enriched than leaf organic components, illustrating that delta13CR was 5.8‰ higher than leaf bulk organic matter on average. However, caution should be taken when predicting vegetation respiratory delta13C on ecosystem level by scaling leaf level results.; In summary, this thesis demonstrated that appropriate upscaling of leaf respiratory properties is critical to quantify canopy and ecosystem level processes.