| | Project DescriptionThe interdisciplinary project between forest growth and wood science looked at growth and wood quality of single trees and stand of 40-year-old Douglas-firs (Pseudotsuga menziesii [Mirb.] Franco). Far beyond its natural range, Douglas-fir has got a lot of attention in Bavaria and Germany. Scientists and practitioners are interested in growth potential and behavior under drought stress. How does this tree species handle longer drought periods? Are there any silvicultural measures to cope these challenges due to climate change? The research project also wanted to close the gap between forestry and wood application. Douglas-fir wood is used predominantly for construction purposes. The analysis describes the impact of the stand density on the quality of the end-product, i.e. wood quality aspects such as knottiness, density, stiffness and strength are relevant. How does silvicultural management affect timber quality? There are modern non-destructive technologies for the assessment of wood quality at different levels of the processing chain. An early, accurate judgement could make the processing chain more efficiently. |
| | Important findings in summary - Douglas-fir can sustain a dry season like in 2003 very well beyond its natural range. The increment fell temporarily, but volume growth recovered already in the subsequent year.
- The more advantageous the site condition, the lower the growth reduction due to drought stress.
- Thinning and low stand density could minimize the growth reduction due to drought.
- Overall, the impact of strong drought stress on basal area and volume growth is less than the impact on height growth.
- Timber quality varies due to genetics, site conditions, silviculture and sawing pattern. The study underlined how strong initial planting density – as a central measure of the silvicultural control – impacts sawn timber quality.
- High initial planting density increases timber strength. Early stand management affects significantly relevant wood properties.
- The increase of planting density from 1000 to 2000 trees per hectare implicated a remarkably high quality improvement.
- The slenderness of young trees is decisive for timber quality and can be regarded as a proxy variable for timber quality.
- Quality is measurable and visible at the levels of trees, round wood and sawn timber.
- The dynamic modulus of elasticity describes wood quality on different levels of the processing chain quite well.
- Integrating quality attributes in a wood growth simulator, the impact of silvicultural measures on both quality and quantity of timber on tree and stand level can be quantified. Hence, consequences of various silvicultural measures can be estimated until the end-product.
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