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RESEARCH PRODUCT

Sensitivity of whole wood stable carbon and oxygen isotope values to milling procedures

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RATIONALE Milling of wood samples is a widely applied preparation method for pooling tree-rings from different trees or periods of several years for determination of δ13C and δ18O values. In this study, whole wood samples were milled using different procedures in order to evaluate potential effects of this preparation method on δ13C and δ18O values. METHODS Subsamples of a 5 cm3 wood piece of a single tree-ring from a lowland white fir were used. The samples were milled with different setups: (i) two and three stainless-steel balls, (ii) 3, 5 and 8 min milling time, and (iii) discontinuous and continuous milling. The δ13C values were measured using an elemental analyser connected to an IsoPrime mass spectrometer and δ18O values using a Thermo Scientific MAT 253 mass spectrometer and a TC/EA connected by a ConFlo IV. RESULTS The results show that varying the milling procedure does not alter the δ13C and δ18O values in comparison to non-milled blank samples. For shorter milling times, an increased variance of δ18O values is recorded, probably caused by isotopic gradient between early- and latewood portions of the tree-ring and thereby biasing the insufficiently homogenised samples. No overheating effects on the δ13C and δ18O values were detected. CONCLUSIONS Milling of wood samples for carbon and oxygen isotope analyses is an appropriate preparation method. Copyright © 2014 John Wiley & Sons, Ltd.