The Dendroclimatological Value of the European Larch (Larix decidua Mill.) in the French Maritime Alps Item Type Article Authors Serre, Françoise Citation Serre, F. 1978. The dendroclimatic value of the European larch (Larix decidua Mill.) in the French Alps. Tree-Ring Bulletin 38:25-34. Publisher Tree-Ring Society Journal Tree-Ring Bulletin Rights Copyright © Tree-Ring Society. All rights reserved. Download date 02/10/2021 03:54:19 Link to Item http://hdl.handle.net/10150/260397 TREE -RING BULLETIN, Vol. 38, 1978 THE DENDROCLIMATOLOGICAL VALUE OF THE EUROPEAN LARCH (Larix decidua Mill.) IN THE FRENCH MARITIME ALPS FRANÇOISE SERRE Laboratorie de Botanique historique et Palynologie, Faculté des Sciences et Techniques St- Jerome, Marseille, France ABSTRACT The relations between the width growth of thousand year old larches of the French Maritime Alps (Vallée des Merveilles, north of Nice) and climate are in- vestigated in several ways. A first analysis of tree -ring width compared with meteorological data of the last 21 years (1954 -1974) reveals above all an inverse relationship to precipitation and temperature for the months of June and July. Moreover the temperature and rain of the autumn (September in particular) and previous winter seem to affect ring forma- tion as well as the temperature and rain of March and May of the current season. Thus comparison of tree -ring width variations - during the thousand year period of tree growth - with climatic data from various sources (history, chronicle, variations of the glacial front lines, known climatic episodes) shows that climate reconstruction, over several centuries, at the limits of the Mediterranean zone, can be obtained with larch of the French Maritime Alps. Les rapports entre la croissance en épaisseur de mélèzes millénaires des Alpes maritimes françaises (Vallée des Merveilles, nord de Nice) et du climat sont recherchés par plusieurs voies. Une premièes analyse des relations de l'épaisseur du cerne avec des données météorologiques des 21 dernières années (1954 -1974) met surtout en évidence une relation inversement proportionnelle à l'importance des pluies et des températures des mois de juin et juillet. De plus, les températures et les pluies de l'automne (septembre en particulier) et de l'hiver précédant la formation d'un cerne paraissent intervenir de méme que les températures et les pluies de mars et de mai de la saison en cours. Compte tenu des résultats acquis, la comparaison des variations de l'épaisseur des cernes au cours du millénaire durant lequel les arbres ont vécu avec des données climatiques issues de diverses sources (chroniques historiques, variations des fronts glaciaires, épisodes climatiques connus) montre que le mélèze des Alpes maritimes françaises est susceptible de permettre une reconstitution du climat, sur plusieurs siècles, aux limites de la zone méditerranéenne. Die Beziehungen zwischen dem Zuwachs von 1000 Jahre alten Lärchen in den Französischen Meeralpen (Tal von Merveilles, nördlich von Nizza) und dem Klima werden auf verschiedene Weise untersucht. Ein erster Vergleich der Jahrringbreiten mit meteorologischen Daten der letzten 21 Jahre (1954 -1974) zeigt vor allem eine negative Korrelation mit Niederschlag und Temperatur der Monate Juni und Juli. Zudem scheinen Temperatur und Regen im vorherigen Herbst und Winter ebenso wie im März und Mai der laufenden Vegetationsperiode die Jahrringbildung zu beeinflussen. Somit zeigt der Vergleich der Jahrringbreitenschwankungen - während der 1000 jährigen Wachstumszeit - mit den Klimawerten verschiedener Quellen (Geschichte, Chroniken, Gletscherbewegungen, bekannte Klimaabläufe), daß eine Klimarekonstruktion für das Mittelmeergebiet über mehrere Jahrhunderte mit den Lärchen der Französischen Meeralpen möglich ist. Whereas numerous studies in dendroclimatology have been published in Europe for regions all situated approximately to the north of the 45th parallel, there are few studies which concern the southern zones and more particularly the Mediterranean area (Gindel 1959; Corona 1973, 1976). For some years at the Laboratoire deBotani- que historique et Palynologie in Marseilles (France) an attempt has been made tofill 25 26 SERRE this gap by experimenting with, on the one hand, typically mediterranean species (Aleppo pine, Pinus halepensis Mill; evergreen oak, Quercus ilex L.; Barbary thuya, Tetraclinis articulata (Vahl) Mast), and, on the other hand, more widespread Euro- pean species which nevertheless grow in the area of Mediterranean influence (Euro- pean silver fir, A bies Alba Mill; European beech, Fagus silvatica L.; European larch, Larix decidua Mill; Scots pine, Pinus silvestris L.; white oak, Quercus pubescens Willd). One of the species in the second group, namely larch - Larix decidua - is the sub- ject of this paper. The larch stand studied is situated in southeast France, to the northeast of Nice (Maritime Alps), approximately one km from the Vallée des Merveilles (Valley of Wonders) - well known for its rupestrian carvings of the Bronze Age (de Lumley et al. 1976). Previous to any analysis, this stand, which is situated on the southwestern limit of the species distribution area and at the upper altitudinal forest border at 2150 m (San- doz and Barbero 1974), seemed liable to exhibit annual ring growth very sensitive to climatic factors. Moreover the trees were enormous (1.0 m diameter on average), visibly weather -beaten but vigourous (Figure 1) and reputedly old; thus it was hoped that long chronologies might be established. Analysis of 31 living trees and seven stumps has shown that the trees are a thou- sand years old. Tree -ring width variations are relatively good (mean sensitivity of 0.23 for all the trees over a period of 1000 years). The material has been treated according tousual techniques of den - drochronology (Stokes and Smiley 1968). Owing to the number and extreme nar- rowness of the rings (0.35 mm average) direct comparison of the core samples and the sections was impossible and therefore the skeleton plot technique (Figure 2) was used to crossdate the living trees and the stumps. Its effectiveness has constituted a first proof on the one hand of the variability of ring width with time, and on the other hand of the homogeneity of the individual responses to factors common to all the trees on the site - among which climate may be considered preponderant. As sampling of the trees took place during summer 1975, all the individual chronologies have been established from the year 1974. Most of the results are based on analysis of the absolute ring widths and not of the corresponding indices. Investigation of relations between climatic variations and tree -ring width varia- tions has been undertaken in various ways. This investigation is not yet completed and the results are open to improvement. First of all, the annual ring -width variations were compared with the available meteorological data for the region as close as possible to the site studied. These meteorological data unfortunately only cover 21 years (1954 -1974) which is evidently not very long in comparison with the long sequence of rings available. However the ecological characteristics of Larix are well known (Fourchy 1952), and we were able to establish some relations (Table 1) using the results of an analysis of cor- respondences (Benzecri et al. 1973; Serre 1973) and a response function (Fritts et al. 1971) for the 21 year period. 1. For Maritime Alps Larix, it seems likely that the main factor influencing ring growth is rainfall in June and July of the current season. The response is inversely pro- portional; high precipitation corresponds to a narrow ring and low precipitation to a Larch in the French Maritime Alps 27 wide ring. The mean temperature of each of these two months cannot be related to ring width. Bearing in mind that Larix "is a species which is not affected by rainfall" (Four - chy 1952), at first sight its response to rainfall is surprising. It is less so when it is remembered that Larix is also a species which transpires abundantly and thus demands high light intensity and dry atmosphere (Fourchy 1952; Sandoz and Barbero 1974). High rainfall together with a humid atmosphere, accompanied by great cloudiness and low light intensity can then explain the formation of a narrow ring; the inverse being equally valid. The narrow rings could also be connected with a number of rain days and higher than average temperatures during these same months of June and July. The inverse is not clear for the wide rings as it is possible that these two factors exhibit more developed synergism when precipitation is high than when it is low. Figure 1. An old tree. 150 loo 50 u II1i I , III I u , 1 i 1 1 1,1 1I I1-dl, I I II I 150 100I 501 ,I IIIIIV I IIll I I i11111111 Figure 2.Collated skeleton plots of two distinct living trees (bark to the right) and of one stump. Larch in the French Maritime Alps 29 Table 1. Ring width and climate relationships. Key: no relationship ( ?) or relationship not established (); climatic factors lower (<) or higher ( >) than the mean (m). Narrow Ring WideRing P >m <m JUNE + JULY Nb. d. R. > m ? T > m ? P <m >m MAY T i > m i (.< mi P (.<m) 1 >m) MARCH T >mi -c m JUNE +JULY+ P ? <m AUG. +SEPT. T > m < m SEPTEMBER P > m < m In -1) T <m >m NOV., DEC. P In -1) < m JANUARY T > m 2. The temperature and precipitation of May and even March of the current season also seem to influence wood production. High temperature and low precipitation cor- respond to a narrow ring and the inverse reaction is also true. The high temperature and greater light intensity, which here again may be infer- red from low precipitation, occur at a time when the tree is leafless but when, accord- ing to Steiner (1967), the water loss should not be underestimated. These factors could bring an increased transpiration of the tree (or could perhaps even trigger this transpiration) at a time when the root system buried in the frozen ground is not yet able to moderate the water loss; it may reasonably be thought that as a result of this a narrow ring is subsequently formed.