Early diagnosis of forest decline: report of a one-year pilot study

There is need for a predictive capability for the early diagnosis and objective quantification of the recent type of forest decline observed over large areas of central Europe. The aim of this initial study is to investigate possible diagnostic tests using material collected from a number of sites exposed to a wide range of pollution climates. Sites for sampling Norway spruce, Scots pine and beech were selected in 7 regions, from southern Germany to north-east Scotland. Techniques were developed during spring 1986, with 2 field trials of sampling and storage methods. Laboratory tests were developed in parallel. Sampling from the selected sites was done from July to the beginning of September. In all, 250 trees were described and sampled. Laboratory tests were performed during autumn 1986. The results showed large differences between the sites for 8 of the techniques used. The patterns showed marked geographical differentiation in at least one tree species. Data from UK sites were often at one end of the range, with data from German sites (showing visible damage symptoms) at the other. Although this association with visible damage is promising, the observed differences could be attributed to genotype, soil type, climate, etc, and are not necessarily related to pollution. Further work with potential tests is required to establish the dependence 'on genotype, sampling conditions and specificity to particular air pollutants. This work will necessitate the experimental exposure of trees to different pollutants under controlled conditions.