Latitudinal gradients in stable hydrogen isotopes of North American trees

Abstract

Stable hydrogen isotopes ({delta}2H values) of plant matter provide information about ambient climate conditions and physiological processes.{delta} 2H values of tree stem wood methoxy groups ({delta}2HTM) are increasingly used to reconstruct the isotope composition of precipitation ({delta}2Hprecip) and temperature variability in mid latitudes regions. However, empirical evidence of the basic latitudinal gradients in North America and their inter-continental context are still missing. We sampled 104 tree cores in 13 North American sites ranging from 38{degrees}-69{degrees}N and investigated the relationship between{delta} 2HTM and{delta} 2Hprecip values. Recorded{delta} 2HTM values are highly depleted in 2H relative to meteoric water and align closely with predictions from a biochemical model. Reconstructed temperature changes, derived from{delta} 2HTM values, agree well with instrumental data in North American since 1932. Our results reveal that the latitudinal gradients of{delta} 2HTM values closely resemble{delta} 2Hprecip values across North America. When combining these spatial patterns with{delta} 2HTM and{delta} 2Hprecip data from Europe a strong correlation (R2 = 0.94, p < 0.001) and a consistent fractionation of -193 {+/-} 13 mUr, representative for Northern Hemisphere mid-to-high latitude sites, is established. The validation across North American and European transects serves as a foundational basis for advancing applications in biogeochemistry and paleoclimate research.