Studies systematically assessing the influencing factors on the nutrition of forest trees and thus, their growth and health, are scarce. Foliar analysis is a precise method, since it provides an exact picture of the nutrient content at a given time.
In the present study, we assessed the nutritional status of two old-growth European beech (Fagus sylvatica L.) stands in Thuringia, Germany, located on different soil types (calcareous cambisol/chromic luvisol versus acidic pseudogley/podzol) using foliar analysis. To capture the growth conditions over time, macro- and micronutrients were analysed from six sample trees of each experimental site over 13 years (2009–2021). To assess potential differences in leaf nutrient concentrations between the two experimental sites and, for each site separately, over time, a one-way analysis of variance (ANOVA) and a repeated-measures ANOVA, respectively, were applied.
The nutritional status of trees at both sites was largely dynamic, and the mean concentrations of most leaf nutrients encompassed a broad range of nutrition levels. Significant time effects were detected for foliar concentrations of K, Ca and Mg (calcareous site) and N, P and Ca (acidic site). Further, at both sites, significant time effects were detected for foliar concentrations of all assessed micronutrients, i.e., Cu, Mn, Fe, Zn. In addition, the time course of some leaf nutrient concentrations was remarkably different at the two sites: e.g., the P concentration showed pronounced fluctuation at the acidic site, whereas it remained relatively stable at the calcareous site, and the Cu concentration tended to decrease over time at the calcareous site, whereas it tended to increase at the acidic site. These results indicate that the interplay of other influencing factors and the concentration of some nutrients is different for the two experimental sites.
The dynamic time course and the differences in time courses between the two sites underline the existence of further relevant influencing factors other than the traditional site factor soil.
In summary, serial foliar analysis over time allows for reliable evaluation of the nutrition status of a forest. Further systematic studies are needed elucidating the impact of other relevant influencing factors including anthropogenic and climate-associated factors.
