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A new method to measure carbon isotope composition of CO 2 respired by trees: stem CO 2 equilibration
Author(s) -
Ubiererea,
Marshall John D.,
Cernusak Lucas A.
Publication year - 2009
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/j.1365-2435.2009.01593.x
Subject(s) - diffusion , biology , ecosystem , carbon cycle , isotopes of carbon , biological system , respiration , isotope , stable isotope ratio , steady state (chemistry) , carbon dioxide , carbon fibers , physics , ecology , thermodynamics , botany , mathematics , algorithm , chemistry , nuclear physics , total organic carbon , composite number
Summary 1. Applying Keeling plot techniques to derive δ 13 C of respiratory input in a closed non‐equilibrated chamber can lead to large errors because steady‐state diffusion rules are violated in a non‐steady‐state environment. To avoid these errors, respiratory δ 13 C can be derived using equilibrated closed chambers. 2. We introduce a new method to obtain stem respired CO 2 δ 13 C (δ st ‐ r ) with closed equilibrated stem chambers (E‐SC). We present a theoretical model describing the equilibration process, test the model against field data and find excellent agreement. The method is further tested by comparing it with closed non‐equilibrated stem chambers (NE‐SC); we found no difference between these methods. 3. Our theoretical model to describe CO 2 diffusion from the respiratory pool into the chamber and the equation to derive the δ 13 C of the efflux are general. They could be applied to other ecosystem components (e.g. soils). 4. Our method is easy to implement, cost effective, minimizes sources of error and allows for rigorous leak detection. One major limitation is its inability to detect rapid change; the equilibration process requires 15 ± 2 h. A second limitation is that it cannot be used for species that produce abundant pitch at sites of stem wounding (e.g. Pseudotsuga menziesii ). 5. Investigating δ 13 C of CO 2 respired by different ecosystem components is necessary to interpret δ 13 C of ecosystem respiration. This parameter has major implications with respect to global carbon cycle science.