A guideline for sample preparation in modern tree-ring stable isotope research

The comprehensive procedure of wood sample preparation, including tree-ring dissection, cellulose extraction, homogenization and packing for stable isotope analysis, is labour intensive and time consuming.Based on a brief compilation of existing methods, we present a methodological approach from pre-analyses considerations to wood sample preparation, semi-automated chemical extraction of cellulose from tree-ring cross-sections, and tree-ring dissection for stable isotope ratio mass spectrometry: the Cross-Section Extraction and Dissection (CSED) guideline. Following the CSED guideline can considerably increase efficiency of tree-ring stable isotope measurement compared to classical methods We introduce a user-friendly device for cellulose extraction, allowing simultaneous treatment of wood cross-sections of a total length of 180 cm (equivalent to 6 increment cores of 30 cm length) and thickness of 0.6-2.0 mm. After cellulose extraction, tree-ring structures of 10 tree species (coniferous and angiosperm wood) with different wood growth rates and tree-ring boundaries, largely remained well identifiable.Further, we demonstrate that tree rings from cellulose cross-sections can be dissected at annual to intra-seasonal resolution, utilizing simple manual devices as well as sophisticated UV-laser microdissection microscopes in a way that sample homogenization is no longer necessary in most cases.We investigate seasonal precipitation signals in high-resolution intra-annual δ18O cellulose values from African baobab, performed by using UV-laser microdissection microscopes.