Schwellenwerte für bodenchemische Präferenz- und Mangelbereiche der forstlichen Hauptbaumarten abgeleitet aus Waldernährungsdaten der BZE II

In this study we present soil chemical preference and deficiency ranges for major tree species on the basis of the German National Forest Soil Survey (BZE II). Furthermore, the expert-based values of the handbook of forest sites classification (Arbeitskreis Standortskartierung 2016) for soil chemistry are examined on the basis of nutritional data. Although there were weak correlations between soil stocks of P, K, Mg and Ca and tree nutrition (r_Pearson between 0.26 and 0.5), nutrient deficiencies were more frequent on poor soils. Species-specific effects generally correspond to the known ecological requirements of tree species. For N and S, the relationships between soil and nutritional data are too weak (r_Pearson < 0.1) for reviewing expert-based values or deriving data-based soil chemical thresholds. The expert values for the soil stocks of P, K, Mg and Ca as well as for the C/P ratio are in a relevant range of tree nutrition. However, for P and Ca, nutrient deficiencies of the deciduous tree species beech and oak are more frequent in soil with medium nutrient stock than for the conifers. In addition, Scots pine appeared surprisingly to be more demanding with respect to the Mg supply of the soil than Norway spruce. The preference and deficiency ranges derived from the data are in the order of magnitude of the total nutrient requirement of 100-year-old stands, with absolute values depending on the species. The presented thresholds can support tree-specific assessments of the soil chemistry of sites and can be implemented into modern forest site information systems. In addition, they provide decision support for a site-specific harvesting intensity and for the choice of tree species, in particular under critical climatic and nutrient conditions. The uncertainties and opportunities for further development of the thresholds are discussed.