Neue Ernährungskennwerte für forstliche Nebenbaumarten Mitteleuropas – Eine statistische Herleitung aus VAN DEN BURG’s Literaturzusammenstellung

Title of the paper: New nutritional threshold values for less common tree species of central Europe – A statistical derivation from VAN DEN BURG’s literature compilation. The determination of nutritional values of leaves and needles is a basic method for the evaluation of physiological conditions of trees and for the assessment of forest health. While for the main tree species older and also more recent nutritional evaluation systems are published, there are hardly any useful assessment schemes for less common tree species. For this reason, on the basis of the extensive literature compilation made by VAN DEN BURG (1985, 1990) also for secondary tree species nutritional threshold values were calculated. This was done using the same methodological approach as developed for the main tree species by GÖTTLEIN et al. (2011). Data availability allowed to calculate threshold values for 15 tree species, including 3 poplar species, 2 species of willow trees, the two native lime trees, and for black pine as the only conifer. For all trees species, the thresholds for normal nutrition for the main nutrients N, P, K, Ca and Mg could be calculated. In many cases, however, data availability did not allow to calculate the threshold between latent and real deficiency. For micro-elements data availability was relatively small, so that, if at all, only thresholds for the range of normal nutrition could be derived. The thresholds given in Tables 2 to 16 are classified according to the quality of the specified values, based on the relative standard error (rSE) of the mean value. Bold print is used for values with rSE lower than 10%, in the case of normal printed rSE is between 10 and 25%, and in italics, a rSE above 25% is indicated. According to UNITED NATIONS (2005), values with a rSE below 25% can be regarded as reliable, values with rSE between 25% and 50% should be interpreted with caution, and values having a rSE greater than 50% are considered as unreliable. Furthermore, according to the calculation scheme of GÖTTLEIN (2016) the nutrient element relations for the range of harmonious and optimal nutrition were calculated for all 15 tree species (Tab. 17). Thus also for some less common tree species, at least for the main nutrient elements, a generally secured evaluation system could be derived providing thresholds for the range of normal nutrition and ranges for harmonious nutrient relations.