Data from: No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

1. Temperate forests are predicted to experience an increased frequency
and intensity of climate change-induced summer droughts and heat waves in
the near future. Yet, while previous studies clearly showed a high drought
sensitivity of different temperate tree species, the vulnerability of the
physiological integrity of these trees remains unclear. 2. Here, we
assessed the sensitivity of six temperate tree species to severe water
limitation during three consecutive growing seasons including the
exceptional 2015 central European summer drought and heat wave.
Specifically, we assessed stem increment growth, sap flow, water
potentials, hydraulic traits, and non-structural carbohydrate contents in
leaves and branches to determine how mature temperate trees responded to
this exceptional weather event and how the observed responses relate to
variation in xylem embolism and carbohydrate economy. 3. We found that the
trees’ pre-dawn water potentials reached their minimum values during the
2015 summer drought and most species reduced their sap flow by up to 80%.
Also, increment growth was strongly impaired with the onset of the drought
in all species. Despite the strong responses in the trees’ growth and
water relations, all species exhibited minimum midday leaf water
potentials well away from values associated with severe embolism (P50). In
addition, we detected no distinct decrease in non-structural carbohydrate
contents in leaves, bark and stems throughout the drought event. 4.
Synthesis: This study shows that mature individuals of six common central
European forest tree species strongly reacted to a severe summer drought
by reducing their water consumption and stopping growth. We found,
however, no indications for xylem embolism or strong carbohydrate
depletion in these trees. This suggests, that xylem embolism formation and
carbohydrate reserve depletion are not routine in temperate trees during
seasonal strong drought and reveals a low vulnerability of the
physiological integrity of temperate trees during drought events as we
describe here.