Root system and the decline of Norway spruce (Picea abies /L./ Karst.)

The paper analyzes the growth and health condition of the root system in declining and healthy trees of Norway spruce in different parts of the Czech Republic. The analyses included stands of all age classes (from young plantations up to stands aged 90 years) from both artificial and natural regeneration. The root system analyses were combined with the analyses of soil chemical characteristics, assimilatory apparatus and weather behaviour. The analyses showed that a predisposition factor to decline in all studied areas was the recent change of weather behaviour. The reason of decline is a very small and conspicuously superficial root system deformed at planting or due to the stratigraphy of soil horizons and soil acidification, which induces negative changes in the nutrition, with magnesium in particular. Fertile sites in lower forest altitudinal vegetation zones exhibit aggressive infestation by honey fungus (Armilaria sp.). Trees from the natural regeneration are more susceptible to decline than trees from the artificial regeneration by planting (trees from natural regeneration have smaller root systems than planted trees of identical height).