Above-ground phytomass and light regime in Norway spruce stands planted with different initial density

Above-ground phytomass and light regime in Norway spruce stands, planted with different initial density (from 0.8 to 200,000 trees ha−1) have been investigated. Two phases of needle mass increment (open-growth and after crown closure, i.e. ecosystem formation) have been singled out. The greater the initial density of stand, the earlier culmination of phytomass increment-from 8–10 years at the initial density of 100,000 trees ha−1, and 24–26 years at the initial density of 3200 trees ha−1. Stand radiation regime follows the dynamics of the above-ground phytomass. At the moment of canopy closure only 40–50% of PAR penetrates through the canopy as compared to open area. The denser the stands, the quicker TPAR decreases. After crown closure, the PAR under the canopy makes up 1% of that in an open area.