We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold for convection, potentially drying tropical land, but this 'upped ante' can be met if sufficient moisture is supplied in monsoon flow. In this framework, the reversal to warming of the subtropical North Atlantic, which is now out-pacing warming of the global tropical oceans, provides that moisture, and explains the partial recovery in precipitation since persistent drought in the 1970s and 1980s. We find this recovery to result from increases in daily rainfall intensity, rather than in frequency, most evidently so in Senegal, the westernmost among the three Sahelian countries analyzed. Continuation of these observed trends is consistent with projections for an overall wetter Sahel, but more variable precipitation on all time scales, from intra-seasonal to multi-decadal.

To provide an inter-continental overview of the floristics and biogeography of droughtadapted tropical vegetation formations, we compiled a dataset of inventory plots in South America, Africa, and Asia from savannas (subject to fire), seasonally dry tropical forests (not generally subject to fire), and moist forests (no fire). We analysed floristic similarity across vegetation formations within and between continents. Our dataset strongly suggests that different formations tend to be strongly clustered floristically by continent, but that among continents, superficially similar vegetation formations (e.g. savannas) are floristically highly dissimilar. Neotropical moist forest, savanna and seasonally dry tropical forest are distinct, but elsewhere there is no clear floristic division of savanna and seasonally dry tropical forest, though moist and dry formations are separate. We suggest that because of their propensity to burn, many formations termed "dry forest" in Africa and Asia are best considered as savannas. The floristic differentiation of similar vegetation formations from different continents suggests that cross-continental generalisations of the ecology, biology and conservation of savannas and seasonally dry tropical forests may be difficult.

ISRCTN71468410.

Sanogo et Kabre. J. Appl. Biosci. 2014. Dynamique de structuration spatio-temporelle des populations de familles de macroinvertébrés dans un continuum lac de barrage -effluent-fleuve, Volta Burkina Faso 6631 ABSTRACT Objective: A monthly sampling of benthic macroinvertebrates was done at the hydro-agricultural of dam Boura in the basin of the Volta (Burkina) during the period of February to July 2012 in order to describe the structuring of insect succession along with changes occurring in habitats of this irrigation system. Methodology and results: The samples of insects were collected from 6 stations placed on the shoreline (Station I), the adjoining zone to the coastline (Station II), the sewage channal (stations III, IV that is located at midsection of the irrigated area and the Station V far away from this area) and the Mouhoun stream (Station VI); the sampling method used conventional method the European Union named " Directive Cadre sur l'Eau (DCE) " advised for the sampling of the benthics macroinvertebrates. The survey revealed a community composed in majority of insects (more of 75%) and sparsely distributed. On one hand at the shoreline and the coastal-adjoining zone in the lake of dam, 23 families of macroinvertebrates were sampled; they mostly belong to the shoreline except for 10 families identified in the adjoining zone to the coastline. These two zones of the dam shelter the same malacological fauna consisting of the families of Unionidae, Lymneidas, Ampullariidae, Planorbidae, Valvatidae and Bulinidae. The survey revealed otherwise that the difference between the biological diversity indices of Shannon of these two zones was more pronounced during the month of July, period of rain in the basin., concerning the dam-sewage channal-river continuum, a total of 35 families were sampled: 27 from dam water and stations near the irrigated zones; and 32 been collected from the station of the sewage channel far from the irrigated perimeter and from the stream. The identification of individuals belonging to the family of the Baetidae and the Ephemerellidae (order of the Ephemeroptera) in the river water highlights a possible reconstruction of biodiversity in the river because both two families are indicator fertile water. Conclusion and application of results: it is concluded of this survey that the agricultural hydro amenities have an influence on the spatio-temporal structuring of the macroinvertebrates. The results of this survey can be used otherwise to keep biodiversity and the restoration of these ecosystems continually impacted

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