Auswirkungen von Duengungs- und Kalkungsmassnahmen auf den CO2- und H2O-Gaswechsel von Buchen (Fagus sylvatica, L.) im Solling : 3. IUFRO - Buchensymposium

Zvolen

1991

S. 193-202

5 Abb., 29 Lit. Ang.

Bandaufführung

75607

During the past years a general compensation liming was carried out more and more to reduce the negative effects of forest soil acidification. To investigate the effects of these measures on a beech forest ecosystem an experimental plot was selected and single fertilized by a high dosis of dolomite lime. This plot is situated in the immediate vicinity of a beech stand (B1 research area of the IBP, International Biological Programme, "Sollingprojekt") which was intensive investigated during the past 20 years. On a second plot an annual fertilization with ammonium sulfate was carried out to investigate the effect of nitrogen deposition on the beech forest ecosystem. The effects of these treatments on the gas exchange were analyzed with a portable steady-state-porometer. On three trees per stand measurements of the CO2- and H2O- gas exchange rate of leaves were taken under natural conditions as well as under controlled light conditions with an artificial light source in order to determine the photosynthetic ability. At the same time continuous measurements of gas exchange of leaves in sun and shade crown of a beech on the B1 area were carried out using a field laboratory equipped with temperature and humidity controlled cuvettes. A correlation was found between the photosynthetic ability and the leaf conductance to water vapour. The leaf conductance strongly depends on the irradiation. Although the cation supply of the limed beech was improved no difference in photosynthetic ability between the beechs of the limed plot and control plot at the same rate of leaf conductance i. e. same stomatal opening occured. These behaviour of the beech was discussed against the backround of their ecological distribution. On the plot with ammonium sulfate ferilization the photosynthetic ability was reduced. The conductivity to liquid water in the root/leaf pathway (hydraulic flow) was calculated from daily patterns of evapotranspiration and leaf water potential. This parameter was also reduced. This result was associated with the observed reduction in fine root biomass and a decreased interconnection with mycorrhizal fungi.