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Tree-ring C-H-O isotope variability and sampling.
1Lab. of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, USA. sleavitt@ltrr.arizona.edu
The Science of the Total Environment
|August 20, 2010
Summary
Tree-ring isotope variability (δ(13)C, δ(18)O, δ(2)H) is influenced by age, genetics, and sampling methods. Standardized protocols are lacking due to varied conditions and research goals, impacting tree-ring data reliability.
Area of Science:
- Paleoclimatology
- Dendrochronology
- Stable Isotope Geochemistry
Background:
- Tree-ring isotope analysis (δ(13)C, δ(18)O, δ(2)H) is increasingly used to reconstruct past environmental conditions.
- Significant variability exists within and among trees, necessitating careful consideration of sampling strategies.
Purpose of the Study:
- To review the factors influencing tree-ring isotope variability (circumferential and among-tree).
- To assess field and laboratory sampling requirements and strategies for tree-ring isotope studies.
- To summarize the state-of-knowledge on juvenile, aging, and genetic effects on isotope composition.
Main Methods:
- Literature review of tree-ring isotope studies.
- Analysis of variability ranges for δ(13)C, δ(18)O, and δ(2)H.
- Discussion of sampling choices: species interchangeability, ring segment selection (whole, earlywood, latewood), and sample pooling.
Main Results:
- Circumferential variability within trees is lower than among trees at a site (δ(13)C: 1-3‰, δ(18)O: 1-4‰, δ(2)H: 5-30‰).
- No single standard sampling or analysis protocol exists due to diverse field conditions and conflicting findings.
- Common practice involves sampling 4-6 trees, avoiding juvenile rings, but cost-effective strategies like pooling samples yield useful data.
Conclusions:
- Sampling and analysis decisions are dictated by study objectives and available resources.
- While analyzing latewood or individual trees offers arguments, pooled samples can be a practical alternative.
- Understanding and accounting for isotope variability sources is crucial for accurate paleoclimate reconstructions.
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