Micro-scale analysis of tree-ring δ18O and δ13C on α-cellulose spline reveals high-resolution intra-annual climate variability and tropical cyclone activity

High-resolution analysis of stable carbon and oxygen isotopic composition (delta C-13 and delta O-18) of tree-ring alpha-cellulose has been increasingly in demand for the study of climate seasonality, droughts, and tropical cyclone (hurricane) activity. The peeling-grinding method commonly used for tree-ring alpha-cellulose preparation is both time-consuming and labor-intensive, and often results in cross-tracheid sampling that masks high-frequency intra-annual climate signals and short-term climate events. Here, we present a new method by extracting tree-ring alpha-cellulose directly from wholewood spline that omits the peeling-grinding step, and allows for micro-scale delta C-13 and delta O-18 analysis that facilitates high-resolution seasonal climate study. This ultrasound-assisted non-destructive extraction method has significantly increased the output of tree-ring alpha-cellulose preparation while retaining the wood cell fabric. Wood cell-wall fibers collected from the alpha-cellulose spline were directly loaded into pre-weighed silver (or tin) capsules and packed, after oven drying, for stable oxygen (or carbon) isotope analysis. A 3.045-mm annual ring subdivided over 26 sections for delta C-13 and delta O-18 analysis revealed remarkable intra-annual isotopic variations (1.62 parts per thousand for delta C-13, and 5.85 parts per thousand for delta O-18). The intra-annual delta C-13 values inversely covary with the seasonal precipitation pattern, suggesting moisture regulation on tree-ring delta C-13 variations. The high-resolution delta O-18 analysis unravels tropical cyclone activities (Hurricanes Frances and Ivan in 2004) that are characterized by an abrupt decline in delta O-18 values by 2.6 parts per thousand with a "V-shape" pattern in tree-ring latewood. An algorithm is developed for establishing regional patterns of tree-ring seasonal delta C-13 and delta O-18 for the study of the mean state of climate seasonality and its anomalies. Published by Elsevier B.V.