Fig. 3.

The fit between modeled and measured Scots pine (a–f) needle water δ¹⁸O, and (g–ad) δ¹⁸O of needle water‐soluble carbohydrates (WSC) with different needle water modeling approaches (see column titles) and model processes affecting δ¹⁸O of needle WSC. In (g–r) the biochemical fractionation factor, ε _wc, is constant (27‰) and in (s–ad) ε _wc is temperature dependent following Sternberg & Ellsworth (2011). In (m–r) and (y–ad) the needle sugar pool size is set according to measurements, while in (g–l) and (s–x) its size is negligible. The dashed line is 1 : 1 and the solid line the linear least squares regression. R ² and MAE denote the coefficient of determination and mean absolute error, respectively. Modeled values are given as mean of 12:00–15:00 h, which corresponds to sampling interval. Error bars indicate the SDs of the five sampled trees.