Eight-year results of precommercial thinning on growth parameters in Picea orientalis (L.) link stands

ABSTRACT The effects of different rates of precommercial thinning (PCT) intensity on the stand developmental parameters in natural Picea orientalis stands were investigated to determine the most suitable thinning rate. The present study was performed in Trabzon province located in the northeastern of Turkey. In PCT plots, four different levels of PCT intensity were applied including control (unthinned), light (1.3–1.5 m spacing), moderate (1.5–2.0 m spacing) and heavy (2.5–3.0 m spacing). The values of diameter and height were measured at the end of the 2010, 2012, 2014, 2016 and 2018 growing seasons. The results indicated statistically significant (p < 0.05) effects of PCT levels on the diameter, total stand volume and total basal area increments in all periods measured. On the other hand, significant differences were at 99% confidence level for 6 and 8-year height increments. Although the diameter increments increased with increasing levels of precommercial thinning, the height increments did not increase. Also, total basal area increments were higher than in the control in all precommercial thinning treatments, except for the heavy PCT. Considering the best results of measured growth parameters, the early results showed that the light and moderate PCT had the most favorable effect on stand development.