Effect of climatic factors on height increment of Scots pine in experimental plantation in Kalsnava, Latvia

Abstract Effects of climatic factors on tree growth are usually determined by analysis of various tree-ring parameters thus focusing on secondary growth. Relationships between climatic factors and height (primary) growth of trees, which is important parameter in forestry and has been linked with geography of species, is poorly studied, mainly due to laborious gathering of data. However, several studies dealing with height growth of Scots pine in Finland showed that climatic factors have a strong effect on height growth. Thus height increment of trees also appears as a valuable proxy for climatological studies. Relationships between height growth of Scots pine in two experimental plantations (local provenance and diallel hybridization experiment) in eastern part of Latvia and climatic factors was determined by dendrochronological techniques. Similarity of high frequency variation of annual height increment (HI) between trees in each plantation was determined by PCA. Effects of climatic factors were determined by correlation analysis. For each plantation two groups of trees were distinguished. These groups showed slight differences in high-frequency variation HI. Height growth of trees from diallel hybridization experiment was sensitive to temperature in early spring and precipitation in dormant period; however, differences in significant climatic factors were observed between groups. Groups distinguished for local provenance experiment differed by mean HI. Both groups showed sensitivity to temperature in May and precipitation in previous July and September; however, fast growing trees showed higher correlation coefficients and additional sensitivity to summer and seasonal amounts of precipitation. As the distinguished groups consisting of trees from different origin or with hybridization patterns, thus the differences in height-growth-climate relationships apparently might be related with individuality of tree growth or different functional traits of trees.