In recent years, species distribution models have been used to gain a better understanding of past and future range dynamics of species. Here we focuse on a keystone species of the North African forest ecosystem (Cedrus atlantica) by calculating a consensus model of the species current geographic potential distribution in North Africa, based on a weighted average method aiming to decrease uncertainty. The consensus model is obtained using seven species distribution model algorithms taking into account twenty-four environmental variables. The model is then applied to several past and future time slices. Past projections refer to the Middle-Holocene and the Last Glacial Maximum, whereas those of future are related to expect conditions around 2050 and 2070.We found that the current potential distribution of Cedrus atlantica is larger than its actual geographical distribution. For some explanatory variables the analysis revealed their importance for the species current distribution. Among all obtained models, that for the Middle-Holocene showed the maximum expansion of the species potential distribution. The Last Glacial Maximum model provided new putative glacial refugia of Cedrus atlantica, not shown by other mechanistic models and palaeorecord localities. Future projections revealed a significant and fast contraction with shifting in altitude of the species range, showing more fragmented areas and even species disappearance in many North African localities.These findings can help to restore cedar forests and conserve them by ex-situ strategies according to the future defined refugia in North Africa. Attention should be paid to the resolution of related output maps, the current biotic interactions and those that may arise under climate change.
Contribution des Légumineuses à la régénération après feu des forêts de Quercus suber et Pinus halepensis du Nord-Est Algérien. -Le rôle des Légumineuses dans la régénération après feu a été largement étudié sur la rive nord de la Méditerranée, mais aucune donnée n'est disponible concernant la rive sud. Le but de cet article est d'analyser la dynamique des Légumineuses dans une subéraie et une pinède à Pin d'Alep du Nord-Est Algérien durant les premiers mois après un feu de faible intensité. Les aspects de la démographie des germinations des Légumineuses, leur contribution à la biomasse totale et la richesse spécifique sont considérés. Les deux communautés ne présentent pas de différences majeures. Toutes deux montrent des modèles démographiques similaires : les germinations de Légumineuses commencent à émerger très tôt (novembre) après le feu (octobre) et continuent à s'établir abondamment avec un premier pic en décembre et un deuxième en mars, avec un ralentissement significatif en janvier et février. La germination diminue à partir d'avril pour atteindre son minimum en mai et complètement s'arrêter en début juin. Ce modèle en deux pics plutôt qu'un seul, comme déjà rapporté, serait vraisemblablement dû au froid exceptionnel durant janvier et février 2005 (neige jusqu'au niveau de la mer) d'où un ralentissement de la germination et son décalage à mars. Huit mois après l'incendie (vers la fin juin, période où la végétation herbacée commence à sécher), la biomasse aérienne des Légumineuses affiche un maximum de 37,8 ± 1,83 g/m 2 dans la subéraie et 26,7 ± 1,63 g/m 2 dans la pinède. Sept mois après le feu, relativement aux autres familles de plantes, les Légumineuses sont floristiquement bien représentées avec 19,8 ± 1,11 % des espèces dans la subéraie et 24,3 ± 2,05 % dans la pinède, valeurs nettement supérieures à celles rapportées pour d'autres écosystèmes de type méditerranéen (3,8 -13,3 %), probablement en raison de la localisation géographique (basse latitude) de notre aire d'étude et la pression de surpâturage qui favorise l'installation des Légumineuses.SUMMARy. -The role of legumes in post-fire forest regeneration has been extensively studied in the northern Mediterranean basin but no published data are available concerning the southern part of the area. The aim of the present paper is to analyse the dynamics of the leguminous species in a Q. suber and a P. halepensis forests in Northeastern Algeria during the first months after a wildfire of low intensity. The aspects of seedling demography of legumes, their contribution to total biomass and species richness were considered. No major differences were detected between the two communities. They presented similar demographic patterns: legume seedlings began to emerge very early (November) after the fire (October) and continued to increase massively with a peak in December and another in March, and a significant slowdown in January and February; in April, they resumed to gradually decrease again to reach their minimum in May and completely stop in early June...
Pinus nigra (black pine) is a Mediterranean taxonomic complex (including different subspecies), with a discontinuous distribution. The southernmost part of its range is in North Africa, in Morocco and Algeria, where it is present as P. nigra subsp. mauretanica. Currently, an extremely limited number of trees of this subspecies still persist within its natural range, giving this taxon an outstanding ecological importance. These residual stands are threatened by many biotic and abiotic factors, putting at risk the survival of this subspecies in its natural habitat. This paper reports for the first time the presence of Eulachnus tuberculostemmatus (Hemiptera: Aphididae: Lachninae) in Algeria, and its infestation on P. nigra subsp. mauretanica. This insect was detected in three sites of the Djurdjura National Park in May 2012 and identified in February 2016. The aphid seems to be responsible for needle discoloration and premature senescence, symptoms observed since spring 2008 on the infested pines. These clusters of P. nigra subsp. mauretanica trees are protected by park regulations, and given their conservation status further investigations into this pest species, and other biotic and abiotic factors that may threaten this important tree, are required.
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