No abstract

Le dépérissement du cèdre de l’Atlas en Algérie est un phénomène complexe qui a affecté les cédraies des Aurès et Theniet El Had depuis les années 1980, et dont les causes restent inconnues. Pour mieux comprendre l’évolution spatio-temporelle du dépérissement du cèdre de l’Atlas et établir une éventuelle relation avec les facteurs du milieu, notre travail s’est focalisé sur la cédraie de Theniet El Had. Ce travail est basé sur deux approches. L’une, spatiale, recense la répartition des arbres dépéris selon l’altitude, la pente, l’exposition, ainsi que leurs paramètres dendrométriques (diamètre, hauteur) et leur état de santé (taux de défoliation). L’autre, temporelle, compare l’évolution de la croissance radiale des arbres dépéris et des arbres sains dans six stations écologiques représentatives des peuplements de cèdre de l’Atlas dans la zone d’étude. Les résultats montrent que le phénomène de dépérissement du cèdre de l’Atlas a davantage marqué la cédraie de Theniet El Had vers sa limite inférieure, dans des stations situées à basse altitude, sur des terrains à forte pente et aux expositions ensoleillées et chaudes. Ce phénomène se présente dans un état avancé, et les arbres dépéris sont des arbres adultes et/ou âgés. Les arbres dépéris se distinguent par une faible croissance et une sensitivité moyenne au climat très élevée. En plus de l’effet de l’âge, la sécheresse prolongée dans la région au cours de la période 1980-2002 a affecté et aggravé l’état de santé du cèdre de l’Atlas. Ces résultats mettent au jour l’urgence d’entreprendre des travaux sylvicoles pour améliorer l’état de santé des peuplements et de mettre en place un dispositif de surveillance de la santé du cèdre.

In North Africa, Cedrus atlantica forests are in decline, following decades of anthropogenic pressure and repeated drought events. Mixed C. atlantica-Quercus ilex stands located in the Theniet El Had National Park (northwestern Algeria) were considered in the present study. Based on a stratified sampling, six temporary plots were established to describe structure (species composition, density, total height, diameter and basal area) and radial growth in relation to type of stand (pure and mixed), using a dendroecological approach. The diameter distribution of C. atlantica indicated the presence of few young individuals and a poor regeneration status in all the stands. The density and basal area of C. atlantica were significantly higher in pure stands, which necessitate silvicultural operations. In contrast, Q. ilex showed a progressive dynamic, at moderate altitude. Radial growth showed a significant decline from 1980 to the 2000s. The absence of an appropriate management plan and the increase in anthropogenic effects, without ruling out a role for the current climate conditions marked by drought, seem to be the causes of C. atlantica decline.

Effet des facteurs stationnels sur la croissance radiale et la réponse du pin d'Alep au climat dans le massif de l'Ouarsenis, Algérie Photo 1. Vue d'ensemble de la zone culminante de l'Ouarsenis où de vastes pinèdes se développent sur substrat calcaire. Photo M. Sarmoum. Correspondance électronique avec les auteurs / Electronic correspondence with authorssarmoum_med@yahoo.fr B O I S E T F O R Ê T S D E S T R O P I Q U E S , 2 0 1 6 , N° 3 2 9 ( 3 ) ABSTRACT EFFECTS OF STATION-SPECIFIC FACTORS ON RADIAL GROWTH AND RESPONSES TO CLIMATE IN ALEPPO PINES IN ALGERIA'S OUARSENIS RANGEThe relationships between climate and radial growth from 1967 to 2010 in nine Aleppo pine stands in the Ouarsenis range (north-western Algeria) were studied according to station-specific factors (substrate, altitude, exposure and age of the trees) using dendro-chronological methods, with an analysis of interannual variations in the thickness of growth rings. A retrospective analysis of radial growth showed high interannual variability in growth ring thickness within the same stand. The statistical parameters calculated showed highly variable radial growth between the different stands, which was related to station-specific factors and to tree age. Average growth ring thickness and persistence declined with the age of the trees. Average sensitivity to climate tended to be greater in trees growing on sandstone or schist substrates than on limestone. Our analysis of the relationships between climate and growth rings shows that the Aleppo pine is responsive to precipitation before or during the formation of growth rings. Higher temperatures, especially when they reach their maximum, have a negative effect on radial growth. The relationships between Aleppo pines and climatic conditions are modulated by station-specific factors, especially the substrate. The most responsive stands tend to be growing on a sandstone substrate. These results provide a useful description to help understand the ecological flexibility of the Aleppo pine and how it responds to climate change, with a view to proposing better ways of protecting pine forests that have been under threat for several decades.Keywords: Pinus halepensis, station-specific factors, radial growth, relationships between growth rings and climate, drought, Ouarsenis. RESUMEN EFECTO DE LOS FACTORES DE SITIO EN EL CRECIMIENTO RADIAL Y RESPUESTA DEL PINO CARRASCO AL CLIMA EN EL MACIZO DE OUARSENIS, ARGELIASe estudiaron las relaciones entre clima y crecimiento radial de nueve poblaciones de pino carrasco en el macizo montañoso de Ouarsenis (Noroeste de Argelia), en el período 1967-2010, atendiendo a factores de sitio (sustrato, altitud, exposición y edad de los árboles) y aplicando métodos de dendrocronología. Se analizaron las variaciones interanuales del ancho de los anillos. El estudio retrospectivo del crecimiento radial indica una alta variabilidad interanual del ancho de los anillos entre individuos de una misma población. Los parámetros estadísti-cos calculados reflejan indican una alta variabili...

Aleppo pine is the most important forest species in Algeria. This species has been used for a long time in reforestation programs, notably the “green dam” planted in the 1970s. Despite this importance, the Aleppo pine continues to undergo all kinds of degradation such as land clearing, illegal cutting and fire. This situation is causing reduction of potential wood production, also jeopardizing the vitality of the stands and their regeneration. This work aims to describe the typology, productivity and dynamics of Aleppo pine stands in the Ouarsenis massif (West of Algeria). 27 plots were installed to describe the stands (composition of forest species, dbh , total height, and basal area). Regeneration was estimated by the rate of juvenile individuals (dbh5cm). The results obtained shows that the Aleppo pine develops different conditions for altitude, climate and type of soil. These conditions have a direct influence on the structure of the Aleppo pine and its productivity. The best populations develop on an average altitude (500 to 1400 m), in subhumid and semi-arid climates, on southern exposures and on limestone soils. The stands are mostly young (age 70 years) with good natural regeneration. These results put focus on the factors of degradation of the Aleppo pine, in particular the recurring fires and the lack of silvicultural management which application can improve the productivity and the vitality of the stands.