Analyse r�trospective de la croissance radiale et mise en relation avec le bilan hydrique dans un dispositif d'intensit� d'�claircie de pin maritime dans les Landes de Gascogne

Abstract

Résumé -En utilisant la technique dendrochronologique, une analyse rétrospective de la croissance radiale a été effectuée en 1998 sur un dispositif sylvicole de pin maritime (Pinus pinaster) des Landes de Gascogne destiné à étudier l'influence sur la croissance de diffé-rents régimes d'éclaircie. Ce dispositif installé en 1967 dans un peuplement de 19 ans, ayant actuellement 52 ans, avait été suivi pendant 12 ans. Il comprend 5 modalités d'intensité d'éclaircie avec 5 répétitions. Cette étude dendroécologique a permis de comparer l'effet des différentes intensités d'éclaircies testées et d'analyser les interactions, dans le contexte pédo-climatique landais, entre l'effet sur la croissance radiale des éclaircies et celui des circonstances climatiques dans lesquelles s'est déroulée cette croissance, essentiellement l'effet des sécheresses estimées par le bilan hydrique calculé pour la saison de croissance correspondante. D'une manière logique, les résultats acquis ont montré que des éclaircies fortes permettaient bien sûr une meilleure croissance radiale mais aussi une meilleure résistance des arbres au stress hydrique « ordinaire ». En revanche, les années de forte sécheresse, ces fortes éclaircies n'ont pas suffi à empêcher une réduction sensible de la croissance radiale ; réduction d'autant plus importante que l'intensité des éclaircies est forte. De plus, pour la tranche d'âge étudiée (20 à 35 ans) l'effet d'une éclaircie ne se manifeste que durant 4 à 5 ans. Sur le plan pratique, ces résultats confirment l'intérêt d'éclaircies fréquentes et d'intensité assez forte compatible cependant, sur le plan économique, avec le maintien sur pied d'un nombre de tige, et donc d'un volume, suffisant. dendroécologie / croissance radiale / Pinus pinaster / intensité d'éclaircie / bilan hydriqueAbstract -Retrospective analysis of radial growth in a Pinus pinaster thinning experiment in the Landes de Gascogne. Relationship with the water balance. A dendrochronological analysis was carried out in 1998, in a Pinus pinaster thinning experiment in SW France. This experiment was established in 1967 (at 19 years old). It consists on 5 thinning intensities with 5 repetitions. Radial growth pattern in each thinning modality has been compared and annual interactions between radial growth and water balance -from Thornthwaite ETP formula -have been studied in the Landes soils and climate environment. At high thinning intensity, trees display higher water stress resistance. Nevertheless, during the years with very low rainfall, radial growth is much reduced in high thinning intensity plots, which is a mesophytic trait. During this thinning experiment, with tree age ranking from 20 to 35, thinning effect duration was no longer than 4-5 years. On a sylvicultural view-point, these results point out the interest of frequent thinning practices (every 4 or 5 years) with an economical equilibrium between high thinning intensity and stand density. dendroecology / radial growth / Pinus pinaster / thinning intensity / water balance Ann. For. Sci. 5...

The effects of thinning intensity and tree size on the growth response to annual climate in Cedrus atlantica: a linear mixed modeling approach

“…This medium-term consequence of thinning has been reported in different species (Misson et al 2003;Kohler et al 2010;Sohn et al 2013) and likely resulted from tree structural changes, such as increased foliage area and fine root biomass (Sohn et al 2013). Benefits of thinning could be maintained by successive operations, as previously suggested by Le Goff and Ottorini (1993) and Timbal (2002) in Fagus and Pinus, respectively.…”

“…This result agrees with Misson et al (2003) and Sohn et al (2013), who found a smaller relative growth reduction induced by severe drought in recently thinned stands. Conversely, Timbal (2002) reported a greater drought-induced reduction in the absolute growth of heavily thinned stands. Kohler et al (2010) and McDowell et al (2006) also reported this higher absolute decrease but additionally emphasized the occurrence of a lower relative decline, in line with our results.…”

“…The effect of competition intensity on the climate-growth relationship was often based on experiments that did not reproduce actual silvicultural guidelines: studies were conducted in stands that had not been thinned for decades (Gea-Izquierdo et al 2009;Martínez-Vilalta et al 2012), in stands thinned once (Misson et al 2003) and in stands lightly thinned (Piutti and Cescatti 1997;Timbal 2002;Kohler et al 2010; but see Olivar et al 2013 andSohn et al 2013). As a consequence, several important aspects of management impact on forest functioning were overlooked: (i) the short-and medium-term effects of thinning, (ii) the cumulative effect of successive thinning and (iii) the prospective analysis of the effect of thinning intensities beyond the current guidelines.…”

Site index curves and growth model for Mediterranean maritime pine (Pinus pinaster Ait.) in Spain

“…The high productivity of the atlantica subspecies gives its forests an important economical value. Therefore, the majority of the recent reports on growth and yield models of the species have been focused on the Atlantic group (Falcão, 1997;Á lvarez-González et al, 1999Á lvarez-González et al, , 2002Rodríguez-Soalleiro et al, 2000;Timbal, 2002).…”

Resin tapping in Pinus pinaster: effects on growth and response function to climate

“…However, in the last decade, dendrochronological methods are increasingly being used to analyze the effects of different factors on the growth of the maritime pine. Studies have been conducted on stands in southwest France (Timbal 2002), the west coast of Italy (De Micco et al 2007), coastal Tunisia (El Khorchani et al 2007), the northwestern Iberian Peninsula (Rozas et al 2011;Vieira et al 2009), central and centraleastern Spain (Bogino and Bravo 2008;Candel-Pérez et al 2012) and the mountains in southeastern Spain (Sánchez-Salguero et al 2010). In general terms, they are quite young forests, very few of them surpassing 100 years of age (Bogino and Bravo 2008).…”