Mixed-effect models to assess potential effect of environmental variables (annual precipitation and elevation) and diameter on δ¹⁸O and δ¹³C composition in C. fissilis and C. odorata. Analyses were separated for annual and 10-year bulk samples. Mixed-effect model results for annual isotope data (δ¹³C or δ¹⁸O with precipitation, sample tree nested in site as random factor).