Results from the generalized linear mixed effects models (GLMM) used to examine the mechanisms influencing δD_F and ⁸⁷Sr/⁸⁶Sr_F.

The relative performance of the mixed-effects versus fixed-effects models was assessed using the difference in the Akaike's Information Criterion for small sample sizes (ΔAICc) and evidence ratios (ER = e0.5*ΔAICc). Mixed effect models included sample location as a random effect in addition to the fixed effect (δD growing season precipitation [δDGS] for δDF and log transformed bedrock age [bedrock] for 87Sr/86SrF).