Sample Collection and Preparation for Annual and Intra-annual Tree-Ring Isotope Chronologies

Abstract

AbstractThis chapter provides guidance for conducting studies based on stable isotope measurements in tree rings to infer past and present climate variability and ecophysiology. Balancing theoretical perspectives of stable isotope variations recorded in tree rings, intended research applications (paleoclimate or ecophysiology) and resource limitations, this chapter describes key aspects of field sampling strategies and laboratory sample processing. It presents an overview of factors influencing variations and thus interpretations of carbon and oxygen isotopes, including juvenile/age effects, canopy status and stand characteristicsto inform sampling strategies that optimize a robust paleoenvironmental and physiological signal with statistically defined confidence limits. Fieldwork considerations include the selection of a study site and trees, field equipment, and sample requirements to recover sufficient material for isotopic measurements, and the desired environmental signal. Aspects of laboratory sample processing include choosing a sampling resolution (e.g. whole ring, earlywood/latewood, thin section, etc.), sample pooling within and between trees, and particle size requirements for chemical extraction and analytical repeatability. Finally, this chapter provides a case study highlighting the potential benefits and limitations of high-resolution sub-seasonal sampling.