Summary1. Disturbances and resource availability are key factors affecting plant diversity in managed forests. As disturbance regimes vary among silvicultural systems and may simultaneously affect different types of resources, effects on biodiversity can be unpredictable. 2. We compared the effects of two silvicultural systems on understorey plant diversity, including species composition, structural attributes and functional organization. One hundred and thirty-five phytosociological relevés were sampled from 27 forest stands managed under either a traditional coppice-with-standards (CWS, n = 12) or a 'close-tonature' selective cutting system (SC, n = 15), over similar edaphic conditions. Important environmental factors affecting vegetation were deduced using Ellenberg indicator values. Structural diversity was described using traditional indices of α and β diversity. Guilds were defined within the local pool of species using a set of 14 traits and their relationship with silviculture was assessed using correspondence analysis. 3. Post-logged CWS stands share some compositional and structural characteristics with selectively cut stands, including high species richness and a dominance of early successional species. However the species pool for all coppicing areas was higher than for selectively cut areas, suggesting that the high disturbance frequency occurring in the latter may progressively eliminate the most sensitive species. 4. Functional diversity strongly differs between the two systems. Although it is conserved through the silvicultural cycle in the coppice-with-standards system, some guilds were lacking in selectively cut stands. The most negatively impacted guilds were tree and shrub saplings, prostrated ruderals, shade-tolerant perennials and vernal geophytes. The latter two comprise 'true forest species' which may also be considered as 'coppicingmaintained species'. To reach the same values of guild richness (i.e. number of guilds) or redundancy (i.e. proportion of the maximal species richness within each guild), larger areas were required in SC compared with CWS systems. 5. In the SC system, the high proportion of light reaching the forest floor induced a spectacular spread of blackberries Rubus fruticosus agg., which decreased species richness. It also caused shifts in guild composition: graminoids and ferns grew strongly to the detriment of true forest species. 6. Synthesis and applications . Our results suggest long-term negative effects of selective cutting on both structural and functional plant diversity, compared with coppice-withstandards. Cutting intervals are shorter than recovery times, so that early successional species-dominated communities are maintained. Vernal geophytes and shade-tolerant perennials seem to be limited by the frequency of disturbance rather than by the severity of disturbance. We conclude that, from a biodiversity point of view, this 'close-to-nature' system does not cope with the objective of sustainable forest management. The rotations currently in use do not match n...

-Forest management consists in anthropogenic disturbances that are able to modulate ecological features, resource availability and successional patterns. Plant communities are thus expected to react differently to contrasted silvicultural systems. We compared plant species composition between stands submitted to a traditional management since many centuries (i.e. coppice-with-standards treatment, stands intensively but infrequently disturbed) and stands recently converted into a selective cutting system (stands moderately but frequently disturbed), over uniform edaphic and topographic conditions. We found significant differences in species composition between both systems. Despite a strong shift in species composition among different stages of the coppice cycle, coppice-with-standards stands supported the highest number of true forest species. Selectively-cut stands were more homogeneous and characterized by ruderal "generalist" species. These fast changes in vegetation composition were related to differences in a group of factors that are directly or indirectly linked to the silvicultureassociated disturbance regime, including soil moisture, soil fertility, forest microclimate, light and game predation. We conclude that the conversion of a silvicultural system which has patterned plant communities since many centuries, induces early major changes in vegetation composition. The most negatively impacted species are the so-called "true forest species" that may be better labelled "coppice-woodland species". disturbance / microclimate / forest management / plant diversity / true forest species Résumé -Changements de la composition floristique induits par la sylviculture dans une forêt tempérée caducifoliée européenne. La sylviculture est une perturbation anthropogène capable de moduler les facteurs environnementaux, la disponibilité des ressources et la dynamique forestière. La végétation spontanée est donc susceptible de réagir différemment à des systèmes sylviculturaux contrastés. La composition floristique de parcelles forestières traitées en taillis-sous-futaie depuis plusieurs siècles a été comparée à celle de parcelles récemment converties en futaie irrégulière coupée « pied-à-pied », en conditions édaphique et topographique uniformes. Malgré des différences importantes en fonction du temps écoulé depuis la dernière coupe, la partie de la forêt traitée en taillis-sous-futaie hébergeait un nombre plus important d'espèces forestières. Les parcelles en futaie irrégulière étaient plus homogènes et caractérisées par des espèces rudérales « généralistes ». Ces changements précoces de la composition spécifique ont pu être reliés à des modifications du contexte environnemental, directement ou indirectement induites par la sylviculture, incluant l'humidité et la fertilité du sol, le microclimat forestier, la lumière et la prédation par le chevreuil. La conversion d'un type sylvicultural, qui a façonné les communautés végétales durant des siècles, induit donc rapidement des changements majeurs dans la compositi...

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This paper is a contribution to the understanding of the West African phytogeography, and particularly the vegetation of Benin. We describe the major vegetation types in Benin using numerical analysis, analyse the chorological differentiation of the flora within them using a phytogeographical index and examine the relations between vegetation types, chorological categories and underlying ecological factors using cluster, correspondence and linear regression analyses. Twenty vegetation types grouped into four geographically separated groups are described and patterned along a south-north climatic gradient. We demonstrate the predictive value of vegetation type with regard to chorological categories and underlying ecological factors. Furthermore, we propose a phytochorological map that represents a synthesis reflecting the vegetation, chorological and climatic patterns in Benin.Résumé.-Ce travail est une contribution à la compréhension de la phytogéo-graphie ouest-africaine en général et de la végétation du Bénin en particulier. Les principales communautés végétales sont identifiées sur la base d'analyses multivariées. Un indice phytogéographique a permis de synthétiser les données chorologiques. Les analyses de régressions linéaires ont permis d'examiner les relations entre les types de végétation, les catégories chorologiques et les facteurs écologiques déterminants. Il est décrit vingt types de végétation regroupés en quatre groupes chorologiques géographiquement séparés le long d'un gradient climatique. La valeur prédictive de la végétation au regard des catégories chorologiques est mise en évidence. Nous proposons une carte phytochorologique représentant la synthèse des relations entre végétation, catégories chorologiques et facteurs écologiques.Mots clés : chorologie -biogéographie -type de végétation -Bénin.

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Résumé.-Une étude de la régénération naturelle d'Isoberlinia doka Craib & Stapf et I. tomentosa (Harms) Craib & Stapf a été réalisée en zone soudanienne au Togo sur 74 placettes de 10 m x 10 m. Elle a permis de montrer que les deux espèces assurent leur pérennité à la fois par voie sexuée et asexuée. Sur l'ensemble des cinq sites étudiés (champs, jachères < 5 ans, jachères de 5 à 10 ans, jachères >11 ans, forêts), on observe en moyenne 32% de régénération par semis, 10,6% par rejets de souche et 57,4% par drageons. Dans les champs et les jeunes jachères, le drageonnage est le principal mode de régénération. Les drageons et les semis naturels favoriseraient beaucoup plus la reconstitution des forêts à Isoberlinia que les rejets de souches. La faculté de la plante à drageonner peut être exploitée sans engendrer de grands frais pour la restauration des peuplements, surtout dans les zones à stress hydrique élevé.Mots clés : Isoberlinia -régénération naturelle -drageonnage -semis -rejetsTogo. Abstract.-Isoberlinia doka Craib & Stapf and I. tomentosa (Harms) Craib &Stapf natural regeneration is studied in the Sudanian zone of Togo on 74 plots (10 m x10 m). The survey show that both species self-maintain by seedlings (32%), stump resprouts (10.6%) and root suckers (57.4%) in five types habitat (fields, fallows less than 5 years, fallows from 5 to 10 years, fallows more than 11 years ,forests). Suckering is the most important in fields and fallows. Root suckers and seedlings are more prone to regenerate the Isoberlinia woodlands than stump resprouts. Suckering is a low cost effective way to restore Isoberlinia forests especially in dry areas.