Despite many studies that have explored the effect of livestock grazing on plant communities, the response of species composition and diversity to livestock grazing in arid rangelands remains ambiguous. This study examined the effects of livestock grazing on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species, perennial species, and all species combined were measured and compared between grazed and grazing-excluded areas. We also examined the relative importance of species turnover and community nestedness. Moreover, the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning.Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where most species composition variation (74%) was due to infrequent species replacement 'turnover' between the two management types rather than nestedness (26%). Results revealed also that among transects, beta diversity was higher in grazed steppes than in grazing-excluded steppes. Whereas, among sites, beta diversity was lower in grazed steppes compared to grazing-excluded steppes. These findings suggest that livestock grazing in arid steppe rangelands increases the variation in plant species composition at a local spatial scale and engenders vegetation homogeneity at a landscape spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large-scale biotic homogenization.

Background Ecological functions and processes in urban ecosystems are governed by various human activities. City-adapted and city-exploiting animal species are expected to present certain specific behavioral and physiological traits in comparison to city-avoiders or conspecific individual frequenting less urbanized or rural environments. A trait of high importance, the plumage color polymorphism has been selected as the main study model and was correlated with different morphological and physiological parameters to highlight its importance in determining the possible health status of urban Feral Pigeons (Columba livia) in North African urban habitats. Methods Different body morphometrics, hematological and hemoparasitic parameters were quantified on free-living Feral Pigeons in urban environments of northern Algeria. Moreover, plumage melanin-based coloration (MBC) was measured and the data collected at the individual scale was correlated with the previous parameters using linear and non-linear modeling approaches. Results Plumage MBC scores of the sampled Feral Pigeons ranged between 0.3% and 74.8%. Among the 12 morphological traits measured, body weight, tail length and total length were deemed to be positively correlated with MBC. Darker morphs appeared to have more hemoparasites compared to lighter pigeons. Quite the same observation goes with the immunity but with non-linear trends. The number of monocytes and granulocytes increased with the increase in MBC levels in lighter morphs, while pigeons with high MBC scores exhibited negative relationships between MBC levels and the number of white blood cells. Conclusions Despite the existence of a number of studies demonstrating phenotypic directional selection, further studies are undoubtedly necessary to understand in detail the underlying mechanisms in species life-history strategies between differently colored individuals. Findings of this correlative study open exciting perspectives revealing that MBC can be considered a good indicator of and health status and adaptation strategies to changes in urban environments.

The diet of a colony of the House Martin Delichon urbica (Linnaeus, 1758), a breeding migratory species in Algeria, was studied from March to July 2004 in the city of Tizi Ouzou, Kabylia region, east of Algiers. It was mainly based on insects, which represented 99.6% of the 3746 food items recovered from 50 faeces. Most preys were winged insects. 178 taxa were identified at different levels, from order to species. Arachnida and Gastropoda were only occasionally captured and hence slightly represented. Hymenoptera dominated (77.6% of individual insects, 97.04% being ants), followed by Coleoptera (15.65%) and Heteroptera (4.99%). Other orders were few in terms of prey. They seemed to be captured only when the House Martin got an opportunity to do so. This study showed monthly variations among the species consumed, indicating a high level of plasticity in the diet. These variations correspond to the local availability and phenology of prey. Most preys are mainly small-sized. The preys of size estimated between 2 and 5 mm found in the fecal bags reflect that of Formicidae consumed by Delichon urbica such as Tetramorium biskrensis, Monomorium salomonis, Tapinoma nigerimum and Plagiolepis barbara. In Kabylia, as elsewhere, the House Martin appears to be an opportunist feeder which, when preys are abundant, selects those that best fit their nutritional requirements, but which can use others and becomes more eclectic when food becomes scarce.

Despite many studies explored the effect of livestock grazing on plant communities the response of species composition and diversity to livestock grazing in arid rangelands remain ambiguous. This study examined the effects of livestock grazing vs grazing exclusion on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species perennial species and all species combined was measured and compared between grazed and grazing-excluded areas. We also verified whether the difference in plant community composition between the two management types was due to species spatial turnover or community nestedness. Besides the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning. Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where the most of species composition variation ~74% was due to infrequent species replacement between the two management types rather than community sub setting ~26%. The analysis of beta diversity at different spatial scales revealed that livestock grazing significantly increased beta diversity at the local scale but decreased it at the landscape scale. Our findings suggest that livestock grazing in arid steppe rangelands increases the variation of plant composition at local spatial scale and engenders vegetation homogeneity at coarse spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large scale biotic homogenization.

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