Root carbon resources determine survival and growth of young trees under
long drought in combination with fertilization
Abstract
Current increases in not only the intensity and frequency but also the
duration of drought events could affect the growth, physiology, and
mortality of trees. We experimentally studied the effects of drought
duration in combination with fertilization on leaf water potential, gas
exchange, growth, tissue levels of non-structural carbohydrates (NSCs),
tissue NSC consumption over winter, and recovery after drought release
in oak (Quercus petraea) and beech (Fagus sylvatica) saplings. Long
drought duration (> 1 month) decreased leaf water
potential, photosynthesis, and NSC concentrations in both oak and beech
saplings. Nitrogen fertilization did not mitigate the negative drought
effects on both species. The photosynthesis and relative height
increment recovered in the following rewetting year. Height growth in
the rewetting year was significantly positively correlated with both
pre- and post-winter root NSC levels. Root carbon reserve is critical
for tree growth and survival under long-lasting drought. Our results
indicate that beech is more sensitive to drought and fertilization than
oak. The present study, in a physiological perspective, experimentally
confirmed the view of Ellenberg (2009) that the European beech, compared
to oak, may be more strongly affected by future environmental changes.