The objective is to assess the influence of atmospheric chemical parameters on physiological processes in forest trees.
The project investigates the determining factors for leaching under controlled conditions in open top chambers. In previous experiments, different foliar leaching rates under winter and summer conditions were found. To confirm these results the investigations will be prolonged for a further 21 month period. In order to allow a more detailed interpretation, investigations into stemflow and nitrogen allocation using nitrogen-15 as a tracer are included.
The influence of ambient air pollutants on physiological and biochemical parameters will be investigated with emphasis put on the vegetation period. The relationships between increased leaching, if any, and long term effects on plant metabolism will be investigated. The experiments screen metabolic parameters which are known to be sensitive. Under low air pollutant concentrations found at the remote, clean air Edelmannshof site, the response of metabolic parameters is not as obvious as in laboratory experiments. Furthermore, they are covered by natural noise. Considered separately, the observed parameters are probably not specific in their reactions to air pollutants, their response may also be triggered by other influences. Combining these parameters, more specific responses of plant metabolism to different stress factors are expected to be obtained.
Continuous measurements of immission and weather data will be performed. Dry and wet deposition will be sampled above the canopy at the top of a 7 m high tower including measurements of air humidity, temperature, PAR and potential evaporation. The results will be analysed for weekly mean values. Precipitation will be sampled weekly above the canopy and below the crown of each tree in the chambers. Soil temperature is controlled by sensors and tensiometers and sucking soil lysimeters are installed.
Samples of 0 year and one year old needles are taken 4 times a year. Each research group uses the identical sample for the analysis of different parameters. The samples will be taken from fully light exposed twigs of the fourth to sixth whorl. Each needle year will be analysed separately. The sampling periods are: before bud break, after bud break, and in the summer and autumn. During extreme immission periods of ozone or sulphur dioxide, additional sampling is planned. In addition, the daily variation of photosynthesis and of enzyme activities and metabolites of carbohydrate and nitrogen metabolism will be measured 4 times a year. The nitrogen-15 experiment will be performed as a short time experiment. It comprises the application of nitrogen-15 fertilizer to one tree and a time course study of the allocation of nitrogen-15 during the following weeks.
Funding SchemeCSC - Cost-sharing contracts