Tree-ring width measurements and isotope data for riparian Populus species, Santa Clara River, 2019

This data set comprises tree-ring data collected from 114 cottonwood trees (Populus trichocarpa and Populus fremontii) within the floodplain of the Santa Clara River, CA. Tree-ring data include annual ring width measurements for all rings of each individual as well as semi-annual (earlywood and latewood) measurements of stable carbon and oxygen isotopes for pure alpha cellulose extracted from annual growth rings corresponding to calendar years 2010-2019 for a subset of 48 individuals. This data set is completed. Carbon and oxygen isotope ratios are reported using “delta” notation (i.e. δ13C and δ18O) calculated by the equation: δ13C (or δ18O) = (Rsample/Rstandard - 1) x1000 where R is the molar ratio of 13C/12C (or 18O/16O), with Rsample being that of tree ring cellulose and Rstandard that of Vienna Pee Dee Belemite (VPDB) for δ13C and Vienna Standard Mean Ocean Water (VSMOW) for δ18O. These data were used for the following publication: Williams, J., J.C. Stella, S.L. Voelker, A.M. Lambert, L. Pelletier, J.E. Drake, J.M. Friedman, D.A. Roberts, M.B. Singer. (2022). Local groundwater decline exacerbates response of dryland riparian woodlands to climatic drought. Global Change Biology.