Humidity Signal Recorded in δ¹³C of Pine Resin and Leaves in Southwestern China

Stable carbon isotope compositions (δ¹³C) in plant materials are an important tool to study variations in the environment that plants live in. δ¹³C in resin has been less explored than in other extensively studied materials, e.g. tree rings, leaves and n-alkanes, with its temporal and spatial variability poorly quantified. Here, we sampled resin from the breast-height stem and leaves at the lower canopy across 80 pine forest plots in Southwestern China (~ 800,000 km²), and examined the climatic signal recorded in δ¹³C in resin and leaves. Our results show a clear humidity signal (e.g. precipitation and aridity index) recorded in resin δ¹³C, much stronger than that preserved in leaf δ¹³C. The climatic signal was strongest when averaged over the previous two growing seasons, suggesting an average turnover time of two years in the stem resin pool. Our results highlight that resin δ¹³C is a promising indicator for spatial variability in climatic signals, so resin can serve as a practical alternative to leaves for δ¹³C-based studies.