The index of theoretical hydraulic conductivity in secondary xylem at breast height of European ash trees, representing different health conditions at time of sampling, over the calendar years 1978–2007. This parameter was estimated from Hagen-Poiseuille equation for each annual increment and calculated as a percentage of maximal average conductivity of healthy trees. The indices were then averaged for 5-y time intervals and for the group of healthy trees (solid line), weakened (dashed line) and dead trees (dotted-dashed line), respectively. Vertical bars indicate standard errors.