Effects of ozone, acid mist and soil characteristics on clonal Norway spruce ( Picea abies (L.) Karst.)—An introduction to the joint 14 month tree exposure experiment in closed chambers

Abstract

This paper introduces a series of publications referring to a single 14-month laboratory study testing the hypothesis that the recent decline of Norway spruce ( Picea abies (L.) Karst.) at higher elevations of the Bavarian Forest and comparable forests in medium-range mountains and in the calcareous Alps is caused by an interaction of elevated ozone concentrations, acid mist and site-specific soil (nutritional) characteristics. The effect of climatic extremes, a further important factor, was not included as an experimental variable but was considered by testing of the frost resistance of the experimental plants. Results of these individual studies are presented and discussed in the following 14 papers. Plants from six pre-selected clones of 3-year-old Norway spruce ( Picea abies (L.) Karst.) were planted in April 1985 in an acidic soil from the Bavarian Forest, or a calcareous soil from the Bavarian Alps. After a transition period, plants were transferred, in July 1986, into four large environmental chambers and exposed for 14 months to an artificial climate and air pollutant regime based on long-term monitoring in the Inner Bavarian Forest. The climatic exposure protocol followed realistic seasonal and diurnal cycles (summer maximum temperature, 26°C; total mean temperature, 9·8°C; winter minimum, −14°C; mean relative humidity, 70%; maximum irradiance, 500 W m −2; daylength summer maximum, 17 h; winter minimum, 8 h). Plants were fumigated with ozone, generated from pure oxygen (control: annual mean of 50 μg m −3; pollution treatment: annual mean of 100 μg m −3 with 68 episodes of 130–360 μg m −3 lasting 4–24 h), and background concentrations of SO 2 (22 μg m −3) and NO 2 (20 μg m −3); windspeed was set at a constant 0·6 m s −1. Plants were additionally exposed to prolonged episodes of misting at pH 5·6 (control) and pH 3·0 (treatment). Simulation of the target climatic and fumigation conditions was highly reliable and reproducible (temperature ± 0·5° C; rh±10%; ozone ±10 μg m −3; SO 2 and NO 2 ± 15 μg m −3).