Évolution de la croissance radiale du hêtre (Fagus silvatica L) dans les Vosges. Premiers résultats sur le versant lorrain

Abstract

Abstract - Changes in radial growth of beech (Fagus sylvatica L) inthe Vosges. Preliminary results from the Lorraine catchment area.Following work on the decline of silver fir (Abies alba Mill) inthe Vosges and beech (Fagus sylvatica L) in the Lorraine plain, whichseemed to show contradictory results, a dendrochronological studyof beech from mixed beech/fir stands in the Vosges was carried out.This paper presents the results obtained for 537 trees from the first85 sites sampled on the Lorraine side of the Vosges. A certain numberof behavioural similarities have been observed for spruce in thesame area and also some differences: i) certain pointer years arecommon to both species but not all; missing annual rings are lessfrequent and rarely successive; ii) the mean growth curve as a functionof age reaches a maximum later than that of fir (at about 40 yearsold instead of 10 years); iii) for a given age, the increase of annualring width for beech is highly correlated to date (the more recentrings are relatively larger); iv) as for spruce, but contrary tobeech in the Lorraine plain, a strong tendency to a long-term increasein ring width was observed. This was in the order of 70% between1850 and 1989, with crisis periods, which always occurred at aboutthe same time. Conversely, the ring-width increase occurred moreregularly than in fir and the plateau in the middle of the 20th centuryis not as clear as that of the fir. In conclusion, the behaviouraldifferences between fir and beech are probably due to a species effect,but environmental differences should be ruled out. The next stageof this study, in which the whole of the Vosges area will be surveyed,will allow us to separate the 2 factors, as well as explain the ecologicalcauses of the different phenomena identified in this initial study.