Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density.

In this work, we studied the effects of early thinning on the radial growth and wood density over a 12-year post-thinning period in Scots pine (Pinus sylvestris L.) trees grown on a site with a rather poor nutrient supply. Ring width, early and late wood width and early wood percentage, mean intra-ring wood density and early-and late wood density were analyzed in 98 sample trees using X-ray microdensitometry. For the analyses, ten different thinning plots with post-thinning stand density varying from 575 to 3400 stems ha -1 were grouped into four classes representing heavy thinning, moderate thinning, light thinning and no thinning. We found that the radial growth in the thinned treatments increased significantly compared to that of the unthinned treatment. Despite this, the mean intra-ring wood density did not decrease significantly as a result of heavy thinning, although it was 2% less, on average (with a range of 1-4% in large and small trees), compared to that of the unthinned treatment. In the lightly thinned treatment, the mean intra-ring wood density even increased by 5%, on average (with a range 4-7% in small and large trees), but in the moderately thinned treatment, the level of change was not as clear. The thinning response of trees representing different status in a stand differed significantly and was also affected by the post-thinning stand density. Altogether, observed simultaneous increases in early and late wood widths and late wood density, but a decrease in early wood density indicate that as a result of heavy thinning, especially, un-uniformity of wood density will increase. On the other hand, although heavy thinning increased tree growth by 9-20%, on average, compared to moderate thinning, which corresponds quite well with business-as-usual management, mean wood density decreased only 0-4% depending on tree status in a stand (from large to small trees). Thus, the decrease observed in wood density was less than expected as a result of heavy thinning at an early stage of stand development, which has recently been recommended as one possible management option in Scots pine in Finland.

Wood quality is of great importance for all of forest industry, because it affects on suitability of wood as raw material for the wood processing industry. In the future, the aim will be to use the right materials for the right end products. For this purpose we need to understand how the material properties of wood are distributed in the stem, and how the properties of wood vary from a tree to tree and from a stand in relation to the genetics, site properties and silvicultural history. Currently, detailed information is lacking how genetic, environmental and forest management influence wood properties (i.e. between and within ring variation). This is although, for example, wood density and equally percentage of latewood, which is known to reduced by faster diameter growth, i.e. larger proportion of earlywood. Wood density reflects also the amount of cell wall material, and it is considered as a key property. It also correlates to other properties of the wood like strength (important for mechanical industry) and pulp yield in terms of the quantity of chemical and mechanical pulp obtained from the volume unit. For the pulp and paper industry, the earlywood/latewood ratio is respectively of great importance, because latewood tracheids of softwoods have thick walls, which increase the density and mechanical strength of wood. On the other hand, considerably more energy is needed in defibration of latewood than earlywood.In the future, it is needed sophisticated tools for intraring wood property analysis, which could give accurate information of intraring properties but still could be reasonable in regard to simplicity of use (time saving) but also in regard to cost. In this context, the general aim of the study was to develop a novel laser based method to produce an unbiased application (mathematical procedure) based on x-ray technique, which will output the shape of an intraring density profile.In this work we investigated HeNe laser light components scattered through small wood samples of Scots pine (Pinus sylvestris L.) by using a diffractive optical element (DOE) based sensor, which was already observed to be effective elsewhere [l4]. The geometric arrangement of the present DOE sensor is shown in Fig.l. The optical signals from DOE sensor were compared with the optical density data of x-ray negatives taken from the respective samples. Good agreement between the x-ray and optical signals was observed when gravimetric density values of Pine samples were considered as shown in Fig.2.

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