Ecophysiological measurements on pollutant stressed Norway spruces in the Open-top chamber experiment "Edelmannshof"

1997

S. 49-76

4 Tab., 14 Abb., 44 Lit. Ang.

Unselbständiges Werk

200104668

From 1988-1992 cmparative ecophysiological measurements were carried out on spruce trees (Picea abies L. Karst.) growing on a natural site in open-top-chambers fumigated with charcoal-filtered and unfiltered air. The ecophysiological measurements described here were part of a multidisciplinary approach, including studies of mineral cycling and a variety of physiological, biochemical and anatomical parameters. The objective of this investigation was to study if there are early changes in tree photosynthesis duririg longterm exposure to anthropogeneous air pollutants measured today in forest areas far from agglomerations which appear before the occurence of visible symptoms. Therefore, several parameters characterizing the performance of the photosynthetic apparatus were determined by studies of light and CO2 response curves on intact branches under controlled climatic conditions. In order to study whether the alterations can be attributed to stomatal or mesophyll responses, diurnal courses of photosynthesis, transpiration and needle water potential under normal ambient conditions were determined. First indications of air pollution effects could been observed during the hot and dry summer 1989 by a reduced photosynthetic efficiency of the youngest needle class, whereas no evidence of effects could be found in 1988. The observed alterations such as a lowered RuBP-carboxylase activity and reduced functioning of electron transport chain became more and more pronounced until the end of the experiment and with increasing needle age class. With respect to inhomogenities in the water supply, it is concluded that the reduced performance of the photosynthetic apparatus of spruce trees growing in unfiltered air can be regarded as a pollutant effect caused by ozone and reinforced by drought periods which occured especially in the years 1989-1991.