Thinning experiments in Norway spruce stands after 40 years of investigation - 1st series

Forestry and Game Management Research Institute at Jíloviště-Strnady has created a new experimental base for thinning research since 1956. A total of 46 experimental series were founded in Norway spruce (Picea abies [L.] Karst.); 24 series are still maintained. This paper focuses on the series established in young Norway spruce stands in 1958 (Rumburk, Mostek, Vim­perk I, Vimperk II and Nisa). The goal of thinning experiment was to compare two basic methods of thinning: positive selection from above (2a) and negative selection from below (3b or 5b). Each experimental series has a control plot (1c) where no thinning was conducted. The effect of thinning by positive selection from above carried out in the 40-year period of investigations was a 10-45% decrease in the abundance of trees in lower diameter classes compared with control plots. Negative selection from below resulted in a more pronounced decrease in thin trees abundance (50-69% compared with control plots). The abundance of thick trees (diameter of 30 cm and more) increased by 5-50% on all comparative plots with thinning. Static stability characterised by the h/d ratio of mean stem and h/d ratio of dominant trees (200 thickest trees per hectare) was influenced by thinning mostly positively (final value of h/d ratio found by the last revision was considerably lower).