THE IMPACT OF THINNING ON DEVELOPMENT OF YOUNG DECLINING SPRUCE STANDS

Early thinning impacts on development of young Norway spruce stands were investigated in areas showing new type of damage. Two treatments such as thinned plots and no-thinning control plots were established in randomized blocks. Besides mensurational characteristics of crop trees (1 000-1 500.ha(-1) marked in both treatments) such as diameter and height growth, yellowing of needles and survival were monitored. The aim of experiment was to confirm or reject a hypothesis about the negative effect of thinning on declining spruce-dominated young stands. After thinning, crop trees reacted positively as they increased their diameter increment within two-three years of investigation while height growth remained unaffected, which contributed to development of more stable (lower h/dbh ratio) stems. No significant effects on yellowing were found in vigorous crop trees of the thinned treatment compared to the unthinned ones. The aim is to get at least 600 crop trees.ha(-1) over the first years after thinning. The study presents results from the initial stage of thinning research - further research to continue monitoring of the crop trees response and conduct following thinning operations is needed.