Radial growth of trees differing in their vitality in the middle-aged Scots pine forests in the Kola peninsula

The research was carried out in unmanaged middle-aged (75-85 years) Northern taiga Scots pine (Pinus sylvestris L.) forests in the Kola peninsula. It was established that forests of green moss-lichen and green moss site types are characterised by a predominance (65-70% by stand volume) of moderately and strongly weakened trees. Trees of differing vitality have significant differences in annual increment. Healthy trees had a radial increment (RI) 70-75% greater than that of dying trees, and a basal area increment (BAI) 85-90% greater. The dynamics of the RI and BAI of Scots pine trees for the 70-year period (from 1945 to 2015) is different. The RI of all individuals in the communities studied decreases consistently. The decrease is expressed more strongly in green moss Scots pine forests (80-95% from 1945 to 2015) compared to green mosslichen forests (60-80%); it manifests itself more in strongly weakened and dying individuals (75-95%) than in healthy and moderately weakened ones (60-80%). Annual basal area increment in green moss Scots pine forests increases by 45-65% from stand establishment until the trees are 25 to 35 years old and subsequently decreases by 50-80% to 70-80 years of age. In green moss-lichen pine forests the BAI of Scots pine remains rather stable in healthy and moderately weakened trees and decreases in strongly weakened and dying individuals by 45% and 75-80%, respectively throughout the studied period.