Nutrient supply and forest decline in Southwest-Germany

Abstract

The analysis of the “high altitude Norway spruce disease” leads to the deficient nutrient supply hypothesis as the dominant predisposing stress factor for the “new type” of forest decline in the research area (Southwest Germany). Photooxidants are seen as inciting factors causing physiological and anatomical damages in the foliage. Together with acid depositions (especially fog), the photooxidants cause increased leaching of the easily mobilized elements. Compensation for increased nutrient losses is possible for the trees depending on the availability of nutrient elements in the soil. The deficiency becomes acute at the time of the highest need of nutrients, i.e. at shoot development when last year's needles turn yellow. As the soil nutrient supply is a decisive factor for the occurence of the forest damages studied an improvement of the nutrient supply by application of fertilizers generally leads to the disappearance of these disease symptoms. Fertilization is therefore a tool to mitigate forest decline when related to an insufficient or poor nutritional status. Fertilization is not an adequate way to fight the “new type” of forest decline as it is fighting the effect and not the cause. It can, however, reduce the impact that air pollution has on forest trees by revitalizing stands and ameliorating soils.