Abbreviations LA = leaf area; SLA = specific leaf area; LDMC = leaf dry matter content; LNC = leaf nitrogen content; carbon:nitrogen ratio = C:N; d 13 C = 13 C isotope content; d 15 N = 15 N isotope content; H max = plant maximal height; A max = carbon assimilation; CWM = communityweighted mean; PCA = principal components analysis; RDA = redundancy analysis. AbstractQuestions: (1) How do community-weighted mean (CWM) trait values of 23 functional traits measured on 34 plant species vary along a gradient of aridity under grazed and ungrazed conditions in an arid steppe? (2) How does variation in our CWM trait values differ from those of more mesic grasslands?Location: Eastern Morocco. Methods:We measured relative abundance and functional traits along a short aridity gradient over two consecutive years at five heavily grazed sites, each with an exclosure preventing grazing. We analysed the relationship between aridity, grazing, and the expression of CWM trait values using ordination methods and a fourth-corner analysis.Results: Unconstrained and constrained ordinations identified three distinct suites of temporally consistent functional traits that co-varied with aridity and grazing, and the fourth-corner analysis identified a number of significant but weak trait-environment associations. Grazing selected for short, fast-growing annual species with high SLA, high pastoral value and low seed mass, while aridity selected for species possessing succulent leaves with high d 13 C leaf content, spines, low LDMC and short stature, although the relative importance of precipitation and grazing changed between years. Conclusions:Although distinct from more mesic grasslands, our study sites exhibited patterns of trait correlations that were similar to the worldwide leaf economics spectrum. These correlation patterns represented three groups that were reminiscent of Grime's C-S-R model. Direct ordinations supported this interpretation. Temporal variation in our results was due in part to precipitation fluctuations. Our results also indicated selection for a grazing avoidance strategy under heavy grazing. Integrating plant functional traits in conservation and management of arid ecosystems represents a novel and challenging task to ensure more sustainable use of these lands.

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Abstract.-The last IUCN evaluation of the sandwort of Marseilles (Arenaria provincialis Chater & Hallyday) places this species in the « Rare » category according to old categories dating back from before 1994. A better knowledge about its natural history now allows us to revaluate its status. This winter therophyte, endemic to Provence, protected by national and international texts, lives in calcareous screes and rocks. After assessing its geographic area and the total number of mature individuals, none of the IUCN criteria version 3.1 (2001) is completely applicable. Nevertheless its extent of occurrence and area of occupancy are limited, and many threats could have a negative effect on its habitat. Thus, we propose the new status "Near threatened" (NT), more or less equivalent to the ancient category « Rare » (R). We therefore strongly suggest a regular revaluation of its status, increasing knowledge, experimental restoration and a global management plan to avoid a deterioration risk. Key words

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Centaurea ibn-tattoui is described and illustrated as a new species from north-eastern Morocco. Intermediate involucral bracts and leaves are the discriminant features separating it from other closely related taxa of C. sect. Acrocentron.