Assessment of Long-term Changes in Timber Quality: Combining National Forest Inventory Data and Growth and Wood Quality Models : Causes and Consequences of Accelerating Tree Growth in Europe. Proceedings of the International Seminar

1999

S. 181-195

6 Abb., 8 Tab., 14 Lit.

Unselbständiges Werk

200059079

In this paper, we proposen to assess timber quality of a standing tree from usual forest inventory measurements such as tree age, height and diameter at breast height (dbh). Growth equations are used to reconstruct the past growth of a tree and to predict its current internal structure, namely ring distribution. These models are linked to allometric equations that estimate the characteristics of branches, to models that predict physical wood properties such as wood basic density from ring distribution and to a glass-log software that simulates the sawing and grading of any board located in a stem whose morphology is known in detail. The French Forest Inventory data for Norway spruce are available at three dates, 1973, 1981 and 1992, respectively C1, C2 and C3. We have chosen one of the most important French districts for Norway spruce in France, the Vosges district, which is located in the North-eastern part of France (58 799 ha and 13 326 000 mß in 1995). The forest area of pure even aged represent almost half part of total Norway spruce area and volumes. Between the first and second forest inventory (C1 and C2), both forest area and total volumes have increased (respectively + 86%). Between C2 and C3 the forest area remains the same but the standing volume has increased consequently (+ 42%) mainly because of the growth of relative young planted stands. At the three inventory dates, the standing volume was respectively 214, 205 and 302 mß/ha for Norway spruce and 350, 324 and 297 mß/ha for fir (Abies alba) which timber is used exactly in the same way than Norway spruce timber. In the second part of this paper we will analyse for C1, C2 and C3, (i) the stands dominant heights for the same stand age classes, (ii) the stand ages for similar breast height diameter classes and (iii) the timber properties for similar breast height diameter classes (25 cm and 40 for example). In the last part of this paper we will discuss the possibility of taking into account the increase of fertility into a stand growth and wood quality model modelling approach.