Regionalizing Nutrient Values of Vegetation to Assess Site Fertility of Mountain Forests in the Bavarian Alps

• Autores: Karl Heinz Mellert, Jörg Ewald
• Localización: Folia geobotánica: A journal of plant ecology and systematics, ISSN-e 1874-9348, ISSN 1211-9520, Vol. 49, Nº 3, 2014, págs. 407-423
• Idioma: inglés
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• Resumen

  • Height growth and productivity of forests depend on temperature, water and nutrients. Ellenberg indicator values that summarize vegetation response to growth factors are suited to predict site fertility. Macronutrients (NPK), as represented by N-values, are a crucial component of site fertility and susceptibility towards biomass extraction. Based on 1,500 vegetation plots from an inventory stratified over all important forest types of the Bavarian Alps we regionalized Ellenberg N-values against area-wide soil, climate and relief predictors including a spatial effect at a scale of 1 : 25,000, resulting in a general additive model (GAM) with eight predictors and an explained deviance of 53 % on test data. The N-value layer was combined with other regionalized indicator values (temperature, reaction, moisture) to predict height of Norway spruce at reference age (site index) of an independent forest inventory data set, resulting in a GAM with an explained deviance of 35 %. After temperature the nutrient value was the second most important predictor of site index and clearly superior to soil reaction. It can be concluded that forest growth is sensitive to reductions of NPK-availability through whole tree harvesting and that maps of N-values deliver important information for planning sustainable harvesting.