(a) Mean radial increment modelled by applying the Gompertz function (n = 3 trees/site). Dots indicate mean ring width determined end of October 2007 at position of point dendrometers. Bars represent standard deviations. Arrows indicate date of budburst. (b) Cambial cell dynamic in 2007 (n = 5 trees/site). (c) Number of enlarging cells determined during the growing season (n = 5 trees/site) and daily radial increment calculated on basis of modelled increment growth. Pearson correlation coefficients are indicated. *** p < 0.001; ** p < 0.01. Dotted vertical lines indicate first determination of enlarging cells in 2007. At that time, dendrometer records were set to zero.