Effects of different pre-commercial thinning strategies on growth in young Scots pine stands

Sammanfattning

Scots pine (Pinus sylvestris L.) is a widely distributed tree species, with a range extending from eastern Europe to far eastern Russia. It is an early-successional, light-demanding species with relatively low shade tolerance, particularly when young. In Scots pine plantations, early competition among seedlings is generally not the main limiting factor in the first years following planting. However, it increases as stand development progresses. Pre-commercial thinning (PCT) is therefore important for regulating stand density and competition, thereby promoting the growth and quality of selected crop trees. The aim of this thesis was to study early stand growth in young Scots pine plantation under different PCT thinning treatments. To address this aim, the experiment was established at Remningstorp estate in southern Sweden, using a completely randomized block design with four blocks. Each block included three treatments, with one plot assigned to each treatment. The treatments were: Control (no PCT), (Tall) thinning with retention of the 1000 tallest trees ha⁻¹, and (Short) thinning with retention of the 1000 shortest trees ha⁻¹. Treatments were based on tree height. The results showed that dominant trees were not influenced by neighbouring smaller trees in terms of mean diameter. In contrast, suppressed trees responded positively to release from larger neighbours, exhibiting a greater increase in both mean diameter and mean diameter growth, than suppressed trees in the unthinned control. Meaning that the release of competition for supressed stems increased the mean diameter and mean diameter growth, compared to stems staying supressed by dominant trees.