Litter-fall and humus accumulation in thinning experiment Kristianov in the Jizerske Hory Mts.

Litter-fall and its accumulation and decomposition in the forest floor are essential parts of the nutrient cycle in Norway spruce [Picea abies (L.) Karst.] stands. The paper is focused on the results from the experiment Kristianov in the Jizerské hory Mts. established in 1986 in the 22-year-old Norway spruce thicket located in the Jizerske hory Mts. (NE part of Czechia). Investigation on the nutrient cycle with respect of thinning was initiated in 2001, when the experimental stands were 37-year-old. Research was focused on two main aspects: humus formation and litter-fall. The thinning regime based on the first very heavy thinning (reduction at the age of 22 years from initially 3 300 to 1100 trees per hectare by negative selection from below) resulted in a significantly lower amount of dry mass in humus horizons L and F under the thinned stand when compared to the control stand 17 years after thinning. Lower humus accumulation under the thinned stand was confirmed by a significantly lower amount of the annual litter-fall in the thinned stand compared to control in the period of 2003– 2006, i.e. 17– 20 years after thinning (39– 42-year-old). These significant differences between variants were confirmed for N and P