Response of the Norway spruce (Picea abies [L.] Karst.) root system to changing humidity and temperature conditions of the site

Abstract

The Bohemian-Moravian Upland shows a large-scale decline and dieback of Norway spruce up to the forest altitudinal vegetation zone (FAVZ) 5. This phenomenon has been observed in the last 7 years and its progress is rapid. Healthy, declining and standing dry trees of equal height were mutually compared in nine forest stands (aged 3-73 years). These parameters were measured: increment dynamics, root system architecture, biomass, fine root vitality and mycorrhiza, infestation by biotic and abiotic agents. Analyses were done for 414 trees, soil characteristics and weather course data covered the period 1961-2004. Warming and precipitation deficit are the predisposition factors. Weakened trees are aggressively infested by the honey fungus (Armillaria mellea), and they die from root rots. In this paper we describe the mechanism of damage to and dieback of the spruce trees concerned.