The role of exotic tree plantations for biodiversity conservation is contested. Such plantations nevertheless offer various ecosystem service benefits, which include carbon storage and facilitation of indigenous tree species regeneration. To assess forest restoration potential in tropical exotic tree plantations, we assessed native cloud forest tree regeneration in 166 plots in ca. 50-year-old plantations of five timber species that are widely used in tropical plantations (Pinus patula, Eucalyptus saligna, Cupressus lusitanica, Grevillea robusta and Acacia mearnsii ). Differences in species abundance, diversity and composition were compared among plantations, and between plantations and disturbed and undisturbed indigenous Afromontane cloud forest (southeast Kenya) relicts after controlling for environmental variation between plots (i.e. altitude, distance to indigenous forest, soil depth, slope, aspect) and for environmental and stand structural variation (i.e. dominant tree height and basal area). Regenerating trees were mostly early-successional species. Indigenous tree species regeneration was significantly higher in Grevillea plantations, where the seedling community also included latesuccessional tree species. Regeneration under Eucalyptus was particularly poor. Acacia had a strong invasive nature, reducing its potential role and usefulness in indigenous forest restoration. Our study underlined that exotic tree plantations have differential effects on native tree species regeneration, with high potential for Grevillea plantations and low potential for invasive exotic species.

No abstract

22Tree species regeneration determines future forest structure and composition, but is 23 often severely hampered in small forest relicts. To study succession, long-term field 24 observations or simulation models are used but data, knowledge or resources to run 25 such models are often scarce in tropical areas. We propose and implement a species 26 accounting equation, which include the co-occurring events extinction, colonization 27 and recruitment and which can be solved by using data from a single inventory. We 28 solved this species accounting equations for the 12 remaining Afromontane cloud 29 forest relicts in Taita Hills, Kenya by comparing the tree species presence among the 30 seedling, sapling and mature tree layer in 82 plots. A simultaneous ordination of the 31 seedling, sapling and mature tree layer data revealed that potential species extinctions, 32 colonizations and recruitments may induce future species shifts. On landscape level, 33 the potential extinction debt amounted to 9% (7 species) of the regional species pool. 34On forest relict level, the smallest relicts harbored an important proportion of the tree 35 species diversity in the regeneration layer. The average potential recruitment credit, 36 defined as species only present as seedling or sapling, was 3 and 6 species for large and 37 small forest relicts, while the average potential extinction debt was 12 and 4 species, 38 respectively. In total, both large and small relicts are expected to lose approximately 39 20% of their current local tree species pool. The species accounting equations provide a 40 time and resource effective tool and give an improved understanding of the 41 conservation status and possible future succession dynamics of forest relicts, which can 42 be particularly useful in a context of participatory monitoring. 43 44 3

This study describes the composition, structure and distribution of coastal dune vegetation near Malindi, Kenya. The vegetation was made up of 156 plant species. Sixty families were recorded with Gramineae (seventeen species) and Papilionaceae (sixteen species) being the most widely represented. Fifteen plant communities were described in the di¡erent geomorphologic units. The plant communities exhibited a distinct zonal distribution. Halopyrum mucronatum and Ipomoea pes-caprae plant communities were common in the unstable geomorphologic units. Cordia somaliensis and Pluchea dioscoridis plant communities were common in the more stable geomorphologic units. Most of the plants in the more stable geomorphologic units were shrubs and trees. Succulent herbs were identi¢ed inthe slacks and the drowned valley, which have moist and damp environments. Re¨sumeC ette e¨tude de¨crit la composition, la structure et la distribution de lave¨ge¨tation des dunes coª tie© res pre© s de Malindi, au Kenya. La ve¨ge¨tation comprend156 espe© ces ve¨ge¨tales. Ona releve¨la pre¨sence de soixante familles, les Gramine¨es (dix-sept espe© ces) et les Papilionace¨es (seize espe© ces) e¨tant les plus largement repre¨sente¨es. On a de¨crit quinze com-munaute¨s ve¨ge¨tales dans les di¡e¨rentes unite¨s ge¨omorphologiques. Les communaute¨s ve¨ge¨tales montrent une distribution zonale distincte. Les communaute¨s ve¨ge¨tales a© Halopyrum mucronatum et a© Ipomoea pes-caprae e¨taient communes dans les unite¨s ge¨omorphologiques instables. Celles a© Cordia somaliensis et a© Pluchea dioscoridis e¨taient communes dans les unite¨s ge¨omorphologiques plus stables. La plupart des plantes des unite¨s ge¨omorphologiques plus stables e¨taient des arbustes et des arbres. On a identi¢e¨des herbes succulentes dans les terres molles et la valle¨e encaisse¨e, la© ouÁ l'environnement est humide.

No abstract