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The aim of this study was to analyse the effects of cambial age, clone and climatic factors (i.e. monthly mean temperature and monthly total precipitation) on ring width (RW) and ring density (RD) development from pith to bark in 30-years-old Norway spruce (Picea abies) grown on a fertile agricultural soil in southeastern Finland. The material consisted of 20 Finnish clones, which represented south, southwest, southeast and central Finnish origins. We analysed the variability of RW and RD among years, individual trees and clones, by fitting mixed models into tree ring series, with a spline function (used to remove the effect of ring age). The results showed that cambial age, clone and mean temperature of July affected both RW and RD. Furthermore, total precipitation of August affected RW and total precipitation of May affected RD. However, these climate variables explained only 1.9% and 3.4% of the total RW and RD variability, respectively. This may be due to the good site fertility with no lack of soil water availability, but also due to relatively short tree ring series available for data analyses. The effect of mean temperature of July on RW varied among clones, but in general, RW increased with increase in temperature. The increase of total precipitation of August increased, in general, RD regardless of the clone, whereas the effect of mean July temperature on RD was much more variable. However, longer time series are needed in the future to provide a better understanding of the interactive effects of the climate variables and genetic origins, in addition to cambial age, on RW and RD development on different sites.

• Introduction The objective of this work was to study how spacing and genetic entry and/or origin group affect radial growth (ring width and cumulative diameter development) and ring density from pith to bark in Scots pine (Pinus sylvestris L.) and in what sense their annual variability could be explained by the climatic variables. The spacing trial was located in central Finland, with current stand density range of 2,000–4,000 trees per hectare. All the six genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus trees from southern, central and northern Finland.

International audience; We studied the differences in branch characteristics along the stems of six different genetic entries of 20 year old Scots pines (Pinus sylvestris L.) grown at different spacing (current stand density range 2000-4000 trees ha−1) in central Finland. Furthermore, we studied the phenotypic correlations between yield, wood density traits and branch characteristics. All the genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus trees from southern, central and northern Finland.* Spacing affected all yield traits, wood density and living branch characteristics such as relative average branch diameter and relative cumulative branch area (p < 0.05). As a comparison, genetic entry affected height, while origin group (southern, central and northern ones) affected most of the studied traits. Regardless of spacing, the northern origin had, on average, the largest stem diameter and highest wood density, while the central one was the tallest one. Furthermore, average branch diameter along the stem was affected by branch age, origin group and spacing, while average branch angle was affected by branch age and genetic entry (p < 0.05).* In general the average branch size could be decreased especially in lower tree canopy by denser spacing during the early phase of the rotation, but only at the expense of tree growth. Correspondingly differences between origins are mainly related to their differences in stem growth.

In forest breeding, stem volume and sawn timber quality have typically been used as the most important selection traits. Less attention has been paid to wood density and fibre properties. This study investigates the effects of genetic entry and spacing on the growth and yield traits, branch characteristics, wood density traits and fibre properties in 20-year-old Scots pines (Pinus sylvestris L.). Additionally, the phenotypic variation within, and correlations between, different traits and the effects of cambial age, spacing, genetic entry and climatic variables on the ring width and ring density development from pith to bark are studied. Kanerva pine (Finnish plus tree S1101) was the father tree for most of the genetic entries included in this study, whereas the mother trees represented Finnish plus trees with a relatively wide geographical range from northern to southern Finland. The effects of genetic entry (mainly full-sib families) and spacing on the growth and yield traits, wood density traits and fibre properties were analysed (Papers I-II) based on materials, harvested in 2006, from 10 genetic entries grown in a spacing trial in central Finland, with a current stand density range of 2000-4000 trees/ha. Furthermore, additional material was harvested from the same trial in 2008 to study the effects of genetic entry and spacing on the branch characteristics (Paper III) and the effects of cambial age, spacing, genetic entry and climatic variables on the ring width and ring density development from pith to bark (Paper IV). In this study wood density traits show lower phenotypic variation compared to growth and yield traits, regardless of spacing. Wood density traits present from moderate to strong phenotypic correlations among them (Paper I). Spacing affects significantly (p

In forest breeding, stem volume growth and sawn timber quality indicators have been used as the most important selection traits for Scots pine, whereas less attention has been given to characteristics such as fibre properties. In the above context, we investigated the differences in fibre properties (i.e. fibre length, fibre width and coarseness) in 20 year old Scots pine (Pinus sylvestris L.) genetic entries as affected by spacing and site, but also the phenotypic correlations between fibre properties, yield and wood density. The study was based on materials harvested from 10 genetic entries grown in a spacing trial (site 1) in central Finland, with a current stand density of 2000 (spacing 1), 2000–2500 (spacing 2) and 4000 trees/ha (spacing 3). In order to study the effects of site, we harvested additional material (4 of 7 genetic entries same as on site 1) from a trial located in southern Finland with a corresponding stand density of 2000 trees/ha (site 2). On site 1, spacing 1 and 3, all average values for analysed fibre properties were similar. In spacing 2 average values were slightly higher. On site 2, the average values for different fibre properties were similar compared to the corresponding spacing 1 on site 1. Spacing affected (p < 0.05) all average fibre properties on site 1; as did also site, when comparing same genetic entries grown on both sites. Regardless of spacing and site, the phenotypic correlations between average fibre length, fibre width and coarseness showed, on average, moderate to strong correlation (p < 0.05). Fibre width showed, in general, low and positive phenotypic correlation with diameter at breast height, stem volume and wood density on site 1. However, as a whole, the ranking of genetic entries changed depending on the trait and spacing considered. Thus, no overall ranking between genetic entries was possible.

In forest breeding, stem volume has typically taken as the most important selection trait, whereas less attention has been given to wood density traits. In this work, we investigated the effects of spacing and genetic entry on the growth, yield and wood density traits in 20 year old Scots pines (Pinus sylvestris L.) based on 10 genetic entries harvested from a spacing trial (stand density range 2000–4000 trees/ha) in central Finland. In order to study also the site effects, we harvested additional material from a trial located in southern Finland (stand density of 2000 trees/ha). Compared to growth and yield properties, wood density traits showed a lower phenotypic variation. Phenotypic correlations among different traits were negative, and mostly moderate to high, suggesting that selection for one trait would simultaneously affect the others. In addition, moderate to strong phenotypic correlations were found among different wood density traits. Stem volume (V) and breast height diameter (DBH) were the largest in widest spacing, whereas in the densest one tree height (H) and latewood percentage were the highest. Genetic entry affected H and wood density traits regardless of spacing. When comparing two sites (with same stand density), genetic entry affected H, whereas site affected DBH and wood density traits. Ranking between genetic entries changed depending on the trait, spacing or site considered. Therefore, no overall ranking was possible. However, we could identify genetic entries having a high V and a relatively high wood density, showing potential for future forest regeneration material.