Inhaltszusammenfassung

We studied the effects of repeated defoliation and drought, which are considered to be most effective in triggering oak decline, on the Central-European oak species Quercus robur L. and Quercus petraea [Matt.] Liebl. Three-year-old saplings were subjected to artificial defoliation in two consecutive years and to drought stress, applied singly or in combination. Differences in the morphological, anatomical and physiological responses to these stress factors among treatments and between species...We studied the effects of repeated defoliation and drought, which are considered to be most effective in triggering oak decline, on the Central-European oak species Quercus robur L. and Quercus petraea [Matt.] Liebl. Three-year-old saplings were subjected to artificial defoliation in two consecutive years and to drought stress, applied singly or in combination. Differences in the morphological, anatomical and physiological responses to these stress factors among treatments and between species were tested in a 3-year experiment. Drought stress lowered the pre-dawn and the afternoon leaf-water potentials in both species, irrespective of additional defoliation. The relative water content of the leaves was unaffected by drought stress; but, in Q. robur, it decreased in trees subjected to defoliation and to the combination of drought stress and defoliation. When repeated defoliation and drought stress were applied within the same growing season, the leaf-to-air difference in the partial pressure of water vapour (w) explained most of the variation in the daily integral of the stomatal conductance to water vapour (g s day sum) in Q. petraea; however, in Q. robur, the hydraulic conductance of the twigs was the most powerful predictor variable. In the same year, the actual hydraulic conductance was correlated with g s day sum in Q. robur, but not in Q. petraea. The studied parameters of gas exchange and biomass production revealed that Q. robur recovered more rapidly from stress than did Q. petraea. We hypothesize that this is due to Q. roburs lower responsiveness to the environmental variable w and its higher responsiveness to internal hydraulic conductance compared to Q. petraea.» weiterlesen» einklappen

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Klassifikation

DFG Fachgebiet:
Pflanzenwissenschaften

DDC Sachgruppe:
Biowissenschaften, Biologie