J. Wolfenden

The nutritional status of Picea abies (L.) Karst. across Europe, and implications for 'forest decline'.

SummaryDuring the summer of 1986, three year-classes of foliage were sampled from approximately 30-year-old Norway spruce [Picea abies (L.) Karst.] trees at 12 sites from S. W. Germany to N. Scotland. At sites in Germany, where trees were showing symptoms of ‘decline’, samples were taken from trees with ‘good’ crown condition and ‘poor’ crown conditon. The distinction between ‘good’ and ‘poor’ was made on the basis of international protocols for defining crown density and foliar discoloration. There was a wide range in nutrient content (percent dry weight) in apparently healthy trees. Current year foliage had ranges of mean values per site: S(0.07–0.13%), N(0.9–1.4%), K(0.5–0.9%), Ca(0.2–0.7%), and Mg (0.05–0.1%). Ranges were greater for 2-year-old foliage: S(0.09–0.18%), N(1.0–1.8%), K(0.4–0.7%), Ca(0.2–1.4%), and Mg(0.03–0.09%). At sites with trees having ‘poor’ crown condition, there were significantly smaller concentrations of Mg and Ca, and larger concentrations of K in 2-year-old foliage from ‘poor’ trees, compared with adjacent ‘good’ trees. Ratios of nutrient content were more significantly related to crown condition within sites than individual nutrients, especially in older needles. ‘Poor’ crowns were associated with larger ratios of N∶Mg, K∶Mg, S∶Mg, K∶Ca and smaller ratios of S∶K and N∶K. A ‘risk index’ is defined for trees showing no visible ‘decline’ symptoms, based upon nutrient content and nutrient ratios, which may be useful in identifying sites liable to experience deterioration in crown condition.With the exception of one German site, where few ‘poor’ trees were observed, the index increases from Scottish sites to English sites to Dutch sites to German sites. The index is empirical, and not necessarily related to potential effects of air pollution. The time dependence of foliar nutrient content may also be useful in diagnosis. At sites with trees having ‘poor’ crown condition, even apparently healthy trees showed a lack of increase in calcium content with needle age, decreases in nitrogen content and very large decreases in magnesium content with needle age. The results show the importance of sampling several year classes of foliage from Norway spruce trees in determining the nutrient status of the tree.

Early Diagnosis of Forest Decline — A Pilot Study

A pilot survey to investigate possible diagnostic tests for the study of forest decline was undertaken during 1986. Samples were taken from sites from S. Germany to N. Scotland, and a wide variety of tests performed. Preliminary results from the most promising diagnostic tests are presented here.