Abdelkrim Si Bachir

Ecological status interactions for assessing bird diversity in relation to a heterogeneous landscape structure

Avian diversity is used to assess the functionality of diverse types of habitats around Salt Lake Djendli, Northeast Algeria. The landscape is stratified into five habitat types in a gradient from wetland to forested mountains. Bird species found in these habitats can be classified into four ecological groups with decreasing degrees of aquatic specialisation and increasing forest specialisation. For each surveyed species, five ecological status were assigned. Overall, there was lower species richness in urban areas compared to other “natural” habitats. Birds have a biogeographical affinity to the western Palaearctic according to the dominant faunal types. Interactions of ecological status with phenological traits reveal that water birds are different from non-aquatic species because most of them are migrants. Moreover, overall, there is no worrying conservation status for surveyed birds. Bird diet is dependent on the ecological status that differentiate bird groups from each other due to differences in the food resources of the habitats they frequent. Phenological categories tend to link together birds of urban and open-lands. These two groups are affected by seasonal human activities. Our findings emphasise the importance of using combinations within the birds’ ecological status, which would give information on the actual state of avifauna. This approach is relevant for future programmes and conservation actions.

Using self-organizing maps to investigate environmental factors regulating colony size and breeding success of the White Stork (Ciconia ciconia)

AbstractWe studied variations in the size of breeding colonies and in breeding performance of White Storks Ciconia ciconia in 2006–2008 in north-east Algeria. Each colony site was characterized using 12 environmental variables describing the physical environment, land-cover categories, and human activities, and by three demographic parameters: the number of breeding pairs, the number of pairs with chicks, and the number of fledged chicks per pair. Generalized linear mixed models and the self-organizing map algorithm (SOM, neural network) were used to investigate effects of biotic, abiotic, and anthropogenic factors on demographic parameters and on their relationships. Numbers of breeding pairs and of pairs with chicks were affected by the same environmental factors, mainly anthropogenic, which differed from those affecting the number of fledged chicks per pair. Numbers of fledged chicks per pair was not affected by colony size or by the number of nests with chicks. The categorization of the environmental variables into natural and anthropogenic, in connection with demographic parameters, was relevant to detect factors explaining variation in colony size and breeding parameters. The SOM proved a relevant tool to help determine actual dynamics in White Stork colonies, and thus to support effective conservation decisions at a regional scale.ZusammenfassungWelche Umweltfaktoren regulieren Koloniegröße und Bruterfolg beim WeißstorchCiconiaciconia?—der Einsatz von Selbstorganisierenden Karten Untersucht wurden Unterschiede in Brutkoloniestärke und Bruterfolg bei Weißstörchen Ciconia ciconia in Nordostalgerien, in den Jahren von 2006–2008. Jede Kolonie wurde anhand von zwölf Umweltvariablen charakterisiert, welche Auskunft über physische Umweltbedingungen, Landbedeckung und menschlichen Einfluss gaben, sowie anhand von drei demografischen Parametern: der Anzahl der Brutpaare, der Anzahl von Paaren mit Küken und der Anzahl flügger Junge pro Paar. Es wurden Generalisierte Lineare Gemischte Modelle und der Selbstorganisierende Karten-Algorithmus (Self-Organising Map, SOM, ein neuronales Netz) angewendet, um die Wirkung biotischer, abiotischer und anthropogener Faktoren auf die demografischen Parameter und die Beziehungen zwischen diesen zu untersuchen. Die Anzahl der Brutpaare und die der Paare mit Küken wurden von denselben (hauptsächlich anthropogenen) Umweltfaktoren beeinflusst. Dagegen wurde die Anzahl flügger Küken pro Paar von anderen Faktoren bestimmt: Weder die Koloniegröße noch die Anzahl von Nestern mit Küken hatten hier einen Einfluss. Die Einteilung der Umweltvariablen in natürliche und anthropogen bedingte half in Verbindung mit demografischen Parametern dabei, die Faktoren zu identifizieren, welche die Variation in Koloniegröße und den Brutparametern erklären. Die SOM-Methode erwies sich als geeignetes Werkzeug zur Beschreibung der tatsächlichen Dynamik in Weißstorch-Kolonien und stellt somit eine Hilfe bei der Festlegung effektiver Schutzmaßnahmen auf regionaler Ebene dar.

Spatiotemporal diversity, structure and trophic guilds of insect assemblages in a semi-arid Sabkha ecosystem

The current study highlights some knowledge on the diversity and structure of insect communities and trophic groups living in Sabkha Djendli (semi-arid area of Northeastern Algeria). The entomofauna was monthly sampled from March to November 2006 using pitfall traps at eight sites located at the vicinity of the Sabkha. Structural and diversity parameters (species richness, Shannon index, evenness) were measured for both insect orders and trophic guilds. The canonical correspondence analysis (CCA) was applied to determine how vegetation parameters (species richness and cover) influence spatial and seasonal fluctuations of insect assemblages. The catches totalled 434 insect individuals classified into 75 species, 62 genera, 31 families and 7 orders, of which Coleoptera and Hymenoptera were the most abundant and constant over seasons and study stations. Spring and autumn presented the highest values of diversity parameters. Individual-based Chao-1 species richness estimator indicated 126 species for the total individuals captured in the Sabkha. Based on catch abundances, the structure of functional trophic groups was predators (37.3%), saprophages (26.7%), phytophages (20.5%), polyphages (10.8%), coprophages (4.6%); whereas in terms of numbers of species, they can be classified as phytophages (40%), predators (25.3%), polyphages (13.3%), saprophages (12%), coprophages (9.3%). The CCA demonstrated that phytophages and saprophages as well as Coleoptera and Orthoptera were positively correlated with the two parameters of vegetation, especially in spring and summer. While the abundance of coprophages was positively correlated with species richness of plants, polyphage density was positively associated with vegetation cover. The insect community showed high taxonomic and functional diversity that is closely related to diversity and vegetation cover in different stations of the wetland and seasons.

Effect of large-scale environmental variables and human pressure on distribution patterns of exotic continental fish in east Algeria.

This study aims to identify large-scale environmental variables that explain the distribution of continental exotic fish across five bioclimatic regions in east Algeria (160,000 km²), North Africa. Fish communities were sampled at 39 sites from 2007 to 2010. Seven environmental variables were investigated: habitat type, altitude, latitude, longitude, bioclimatic region, minimum and maximum air temperatures and human pressure. The common carp (Cyprinus carpio Linnaeus, 1758) and the silver carp (Hypophtalmichthys molitrix Valenciennes, 1844) were the most widespread exotic species. Almost all exotic fishes were distributed over desert and sub-humid bioclimatic scales. Reservoirs represent the type of habitat that houses the greatest exotic species richness. The distribution pattern of exotic fishes was mainly predetermined by the type of habitat. Alien ichtyofauna colonizes primarily man-made hydrosystems regardless of environmental variables or the degree of human pressure, making these habitats more vuln...

Diversity and bioprospecting of extremely halophilic archaea isolated from Algerian arid and semi-arid wetland ecosystems for halophilic-active hydrolytic enzymes

The diversity of haloarchaea associated with different dry salt lakes in northeastern Algeria was investigated together with their potential of hydrolytic enzyme production. A total of 68 aerobic halophilic archaea were isolated from saline sediments. Based on the 16S rRNA gene sequencing, the isolates were assigned to seven phylotypes within the class Halobacteria, namely Haloarcula, Halococcus, Haloferax, Halogeometricum, Haloterrigena, Natrialba, and Natrinema. The results showed that Haloferax group was found to be dominant in all samples (30 isolates) (44%) with high diversity, followed by Halococcus spp. (13%) (9 isolates). All phylotypes are extreme halophiles and thermotolerant with the ability to grow at temperatures up to 48 °C. In addition, the screening for extracellular halophilic enzymes showed that 89.7% of the isolates were able to produce at least two types of the screened enzymes. The strains producing esterase, gelatinase, inulinase, cellulase and protease activities were the most diverse functional group. These data showed an abundant and diverse haloarchaeal community, detected in Algerian wetland ecosystems, presenting a promising source of molecules with important biotechnological applications.

Effet du climat et de l’exposition sur la dynamique des populations de la cochenille violette, Parlatoria oleae Colvée (Hemiptera : Diaspididae), en conditions arides

Résumé Ce travail a pour objectif l’étude de quelques aspects bio-écologiques de la cochenille violette, Parlatoria oleae Colvée 1880, bio-agresseur des cultures de l’Olivier en régions arides. Le suivi du cycle biologique ainsi que la démo-écologie de ce ravageur ont été réalisés grâce à des dénombrements périodiques des populations sur les différents organes de l’arbre (méthodes de Vasseur & Schvester) de décembre 2010 à décembre 2011 dans la région d’Ain Touta (nord-est algérien). L’espèce y a montré deux générations par an : une génération printanière se développant entre avril et juillet et une génération automnale évoluant entre août et octobre. La ponte débuta en avril et s’échelonna jusqu‘à la fin septembre. L’exposition nord est la plus favorable à cette diaspine qui y trouve des conditions microclimatiques optimales pour son développement. La ponte moyenne est de 8 à 9 œufs par femelle. L’analyse statistique de l’effet des conditions climatiques étudiées (températures minimale, maximale et moyenne ; précipitations, gelée et indice d’aridité De Martone) sur les effectifs des différents stades, montre une grande variabilité d’un stade à un autre. L’analyse statistique établie révèle également que les effectifs de l’espèce présentent des variations très hautement significatives selon l’orientation dans l’arbre d’olive colonisé.

Variation in bird assemblages along an agricultural intensification gradient: a case study of olive orchards in north-eastern Algeria

Abstract Despite the fact that the Mediterranean basin is considered to be a global biodiversity hotspot for flora and fauna, studies investigating the benefits of agri-environmental schemes on biodiversity conservation in perennial agro-ecosystems in this region are scarce, particularly for bird communities in North Africa. This study investigated the effect of agricultural intensification on bird assemblages in olive orchards in north-eastern Algeria. Bird counts were conducted along an agricultural intensification gradient during twelve consecutive months (from March 2014 to February 2015). Accumulation curves and non-parametric estimators for incidence-based data were used to estimate the total species richness of birds. GLMMs, PERMANOVA and non-metric multidimensional scaling analyses were conducted to evaluate and to visualize the variation in species composition among the studied sites during the breeding and non-breeding seasons. Overall, the total species richness of birds decreased with the increasing level of agricultural intensification. Additionally, among the three trophic guilds (insectivore, granivore and omnivore), the frequency of occurrence of insectivorous and granivorous birds tended to decrease with increasing agricultural intensification. We explored possible reasons for the observed patterns, in relation to differences in the intensity of agricultural management, between the olive orchards studied. This study provides the first qualitative data, which suggests that less intensive agriculture can enhance avian diversity, particularly of insectivorous and granivorous birds, in olive orchards in Algeria.

Population increase and nest-site selection of Cattle Egrets Bubulcus ibis at a new colony in drylands of north-east Algeria

Colony occupation by Cattle Egrets Bubulcus ibis at an arid location in north-east Algeria lasted from mid-March or April to August. The colony, which was founded in 2003, increased from 124 pairs in 2007 to 250 pairs in 2011 and the density of nests from 0.36 to 0.73 nests m−2 in the same period. The number of trees used for nesting increased from 16 trees in 2007 to 40 in 2011. The average height of nesting trees ranged from 12.8 士 3.0 m in 2007 to 13.6 土 2.9 m in 2011, whereas the average height of nests varied between 11.5 土 2.5 m and 13.2 土 2.9 m. Cattle Egrets built their nests mainly on strong primary branches of trees (30%) or secondary branches at the periphery of the trees crown (29%). Numbers of nests sited in a tree were significantly influenced by the species of tree and the diameters of its trunk and crown, as well as by the horizontal and vertical positions of nests within the tree.