Figure 4

Relationship between residual Δ13C and mean annual precipitation (log transformed MAP) and the square root of elevation. For the plot with mean annual precipitation, residual Δ13C is calculated relative to a model that only includes the effect of elevation. Similarly, for the plot with elevation, residual Δ13C is calculated relative to a model that only includes the effect of precipitation. Global observations from previous work28 in black, P. balsamifera observations (this study) in grey.