Distribution, Age and Growth Dynamics of Scots Pine Recruits on Its Northern Distributional Limit in Norway

Growth and age structures of Scots pine (Pinus sylvestris L.) at its northern distribution are influenced by both regional climate and microsite conditions. While large-scale trends for stand regeneration and annual growth are known to be tightly related to summer temperatures and precipitation, these may not always reflect the local responses. Scots pine recruits were sampled in three locations along the northern distributional limit in Nort-East Norway in August 2022. The locations represent the three approximate positions of East, South and West of the distribution limit. I then compared the age structures and growth between a Core site in forest stands and an Edge site at the distributional limit of each location. Ages where significantly different between the different locations and the Core and Edge site for each. Four sites had a multimodal age structure typical of a periodical recruitment success, while two had a unimodal distribution. A GLMM revealed how the ring width in the first 10 years after establishment did not differ significantly between recruits from different locations or within the East and South sites. It however resulted significantly higher for the Edge site within the East location. Vertical growth was surprisingly higher in all Edge sites. With both radial and vertical growth showing higher values in the Edge sites, the results suggest that variations at microscale might be more important than regional climate on the regeneration and growth rates.