CONTINUOUS MONITORING OF GAS-EXCHANGE IN OPEN-TOP CHAMBERS IN POLLUTION EXPERIMENTS - METHODOLOGICAL ASPECTS

As part of an experiment on effects of atmospheric pollution on the ph ysiology of spruce trees (Picea abies (L.) Karsten), a method for cont inuous monitoring of gas exchange of young trees grown in Open Top Cha mbers (OTC) was developed. The basic principles and feasibility of thi s method are first presented in detail. The installation of a fine per forated polyethylene net over the top of the OTC, in order to reduce i ngress of outer air, made it possible satisfactorily to monitor the ga s exchange of the trees over long periods. Examples are given of typic al measurements of net assimilation and transpiration fluxes for an ex perimental canopy of 15 young spruce trees to show diurnal and seasona l variation.