Response to different thinning intensities in young Pinus sylvestris

The study reports on the growth of Scots pine (Pinus sylvestris L.) following the first commercial thinning. The study material consisted of 10 plots, each 1200 m2 in area, which were subjected to low‐thinning resulting in varying retention‐stand densities. The post‐thinning diameter growth of the trees correlated positively with the harvested competition and negatively with the retained competition. However, the variables describing removal were not useful model predictors in distance‐dependent single‐tree growth models; the models based on the retained competition only were equally good as models including removal as an additional predictor. In the study thinning response is defined as the change in growth rate as a result of the thinning. The 5‐yr thinning response correlated positively with the harvested competition and negatively with the retained competition, but the correlations were weak. The 5‐yr thinning response did not depend on relative or absolute tree size. Analysis of the temporal distribution of the thinning response revealed that the response was different in different size classes and in different classes of retained and harvested competition. The absolute and relative increase in diameter growth was at its highest among co‐dominant and medium‐sized trees, while the smallest trees were the quickest to respond but demonstrated the lowest total response. The relative change in diameter growth was at its smallest among the largest trees.