Grenzwertbereiche für die ernährungsdiagnostische Einwertung der Hauptbaumarten Fichte, Kiefer, Eiche, Buche

For the four main central European tree species spruce, pine, beech and oak all commonly used nutritional classification systems were compiled and evaluated for each element by calculating percentiles. With this procedure a range (25% to 75% percentile) as well as the central value (50% percentile = median) were chosen to characterise the threshold values for deficiency symptoms, as well as the lower and upper threshold for the range of normal nutrition. The values given in Tab. 1 (macro elements) and Tab. 2 (micro elements) thus represent for each element and species the most probable range respectively value derived from the different classification systems. However, the validity of these values cannot be proved. As a rule, with only few exceptions, the range of the 25 to 75% percentile is more narrow for the threshold defining symptoms than for the border of normal nutrition. This is mainly due to the fact, that it is much more easy to detect symptoms than to evaluate "normal" nutrition. In Tab. 3 the quality of the different classification systems is checked by determining the proportion of the values of each system falling into the ranges given in Tab. 2. The classifications systems of BMELF (1995) and CROISE et al. (1999) show a good accordance for spruce, ARBEITSKREIS STANDORTS - KARTIERUNG (2003) for pine, EVERS (unpublished) and HÜTTL (1992) for beech and CROISE et al. (1999) for oak. With the exception of beech also the system of GÖTT LEIN et al. (2011), which is based on the large dataset of VAN DEN BURG (1985, 1990), provides a high number of values within the most probable range. Splitting the dataset of beech into values for young and adult trees (data given as appendix) clearly improves its quality. For spruce, pine and beech the values for adult trees match better to the overall evaluation than those for young trees, indicating, that the newly derived threshold values should only be applied for mature trees. The practical application of the new values, derived by a meta-analysis, in comparison to the existing classification systems will indicate, whether they enable a more plausible evaluation of the nutritional status of our main tree species.