LAUSR

The present paper is the first contribution from the biomass quantification series which is realized by Forestry and Game Management Research Institute in the Krusne hory Mts. (Northern Bohemia). This study is aimed at blue spruce substitute stands. Research was done within the blue spruce experiment Flaje II in the Krusne hory Mts. (800 m above sea level in the spruce forest vegetation zone, acidic category). Results showed that the aboveground biomass of the investigated substitute blue spruce stand without thin - ning amounted to approximately 56 thousand kg of dry matter per ha at the age of 22 years. Wood and bark of branches are the most important parts of the aboveground biomass (ca 40%). Needles and stem wood accounted for approximately 26 and 28% and stem bark only for 6%. At the age of 22 years, the investigated substitute blue spruce stand accumulated: N - 336 kg, P - 28 kg, K - 138 kg, Ca - 159 Mg - 28 kg per hectare. Thinning with the consequent removal of aboveground biomass (54% of trees, 40% of basal area at the age of 16 years) represented a loss of ca 8.7 thousand kg/ha of total biomass, which contained 53 kg of N, 5 kg of P, 22 kg of K, 26 kg of Ca and 4 kg of Mg. The removal of biomass in areas previously degraded by acid deposition may result in the deficiency of Ca and Mg because of their low content in forest soil. On the other hand, thinning supported the faster growth of trees left after thinning and consequently faster biomass and nutrient accumulation.