Leading researcher: Dr. László Tolvaj
Collaborators: Dr. Edit Barta, Dr. Antal Kánnár, Dr. Krisztián Andor, Enikő Baróti
Many researchers investigated the effect of CO2 concentration increase on the growth of trees during the last two decades. The effect of elevated CO2 content on the anatomical, physical and mechanical properties of wood was examined under artificial conditions. In some tests, the temperature was elevated, too or the soil nutrient content was modified.
Most of the investigations demonstrated the increase of the annual ring width and the increase of the timber volume. The radial increase of the trunk and the volumetric increase were considerably higher under elevated CO2 concentration than under normal condition. The presence of nitrogen promoted the increase of the timber mass. Mainly the increase of earlywood part was remarkable where the thinner cell walls and the larger vessels are located. The density decrease of resin canals was found in case of Scots pine. Some investigations have demonstrated that elevated CO2 concentration modified the microfibril angle resulting in the decrease of juvenile wood part. The elevated temperature increased the fiber length. The hemicellulose content decreased while the lignin content increased at higher temperature, significantly.
The published results are not identical in the case of density and mechanical properties. The reason of this discrepancy is the diversity of the applied conditions. Most of the researchers found that the concentration of carbon dioxide does not affect considerably the average density and the modulus of elasticity of wood. However, the density of the latewood increased in case of higher CO2 concentration. Other investigations found the decrease of the earlywood density in CO2 rich condition. The acidic soil produced denser, harder and more rigid wood in elevated CO2 concentration. The published mechanical data can not be considered as universal because the examined trees were young (less than 20 years).
In the recent study, we are going to examine the anatomical, physical and mechanical properties of the annual rings in an approximately 100-year interval. We seek for the parameters affected by the climate change. Samples were collected from the forests surrounding Sopron. Disks were cut from sessile oak, European oak, Turkey oak, beech and spruce trees at a height of 3-5 meter. 3 samples were selected from each species. The oldest tree was 121 years old while the youngest was 65 years old. Sample preparation goes on.
Beside the examination of the anatomical properties, the annual ring density profile will be examined by nail shooting method. The hardness of each annual ring will be measured. The average compression strength of 8-10 annual rings will be measured and the modulus of elasticity will be calculated. We are going to cooperate with Dr. Imre Berki (task III.2.) to analyze the annual ring structure. Later on, we will measure the physical and mechanical parameters of his samples as well.