title: Sensitivity of whole wood stable carbon and oxygen isotope values to milling procedures.
abstract: BACKGROUND
  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 δ(13)C and δ(18)O values. In this study, whole wood samples were milled using different procedures in order to evaluate potential effects of this preparation method on δ(13)C and δ(18)O values.
  
  
  METHODS
  Subsamples of a 5 cm(3) 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 δ(13)C values were measured using an elemental analyser connected to an IsoPrime mass spectrometer and δ(18)O 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 δ(13)C and δ(18)O values in comparison to non-milled blank samples. For shorter milling times, an increased variance of δ(18)O 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 δ(13)C and δ(18)O values were detected.
  
  
  CONCLUSIONS
  Milling of wood samples for carbon and oxygen isotope analyses is an appropriate preparation method.
authors.affiliation: Department of Geography, Johannes Gutenberg-University Mainz, Johann-Joachim-Becher-Weg 21, 55128, Mainz, Germany; Institute for Geosciences, Johannes Gutenberg-University Mainz, Johann-Joachim-Becher-Weg 21, 55128, Mainz, Germany.
authors.forename: Dana F C
authors.initials: DF
authors.lastname: Riechelmann
authors.forename: Michael
authors.initials: M
authors.lastname: Maus
authors.forename: Willi
authors.initials: W
authors.lastname: Dindorf
authors.forename: Bernd R
authors.initials: BR
authors.lastname: Schöne
authors.forename: Denis
authors.initials: D
authors.lastname: Scholz
authors.forename: Jan
authors.initials: J
authors.lastname: Esper