Abstract
Background and aims – Eighty per cent of Gabon's territory is covered by forest with most species inventory work focused on these areas. However, herbaceous open vegetation types are abundant in this country and can be found in savannas on the coast, in the centre and in the south, and on inselbergs. The species diversity patterns of these habitats remain largely unexplored yet are targeted for both conservation and development. Here, we evaluate the floristic diversity of savannas in Gabon, their affinities with the inselberg open vegetation, and their contribution to the national park system in Gabon, which is currently undergoing a gap analysis. We then use a case study from the Bateke Plateaux to demonstrate species rarity in a single savanna. Materials and methods – Species presence in the grassy formations of the savannas in Loango, Lope, Pongara, and Plateaux Bateke national parks and in Kum inselberg is compared using ordination and clustering based on a similarity matrix (Sorensen index). For the Bateke Plateaux savannas, the species rarity and distributions are assessed using Star ratings. Key results – The species in the open herbaceous vegetation in Gabon account for at least 11% of the total flora of the country (508 species out of 4,710). Except for the coastal savannas, all sites are highly dissimilar in floristic composition (Sorensen index 0.065–0.26) and no dominant savanna type occurs within the dataset. The inselberg site is the most dissimilar and constitutes a separate vegetation unit. Most savanna species of the Bateke Plateaux area are widely distributed, but not weedy. A few are extremely rare and are linked with moist habitats, substrate, and fire occurrence. Our results show the diversity and the conservation value of open, herbaceous habitats. Currently, the Gabonese National Park network is partly protecting the savanna and inselberg vegetation. However, several areas remain un-assessed and merit further exploration.
Highlights
The flora of Gabon is estimated to comprise as many as 7,000 species (Sosef et al 2006) with most of the country being covered by forest
We present here the first floristic comparison of the open herbaceous vegetation of Gabon, asking five questions: (1) what is the overall contribution of these species to Gabon’s floristic diversity, (2) how does species composition differ amongst geographic areas, (3) are inselbergs grassland savanna islands? (4), do some savannas contain globally rare species? and (5) what is the contribution of these floras to Gabon’s national park system?
All star ratings and the data matrix can be found in the online supplement. This analysis suggests that despite the fact that open herbaceous vegetation is present on inselbergs, the flora of these inselberg micro-habitats is very different from the savanna flora
Summary
The flora of Gabon is estimated to comprise as many as 7,000 species (Sosef et al 2006) with most of the country being covered by forest (estimated at 80%). While several studies have focused on forest diversity patterns (Hardy & Senterre 2007, Parmentier et al 2007), few have considered open areas such as savannas. Collections from these areas continue to be of low density, and specialists working on the Central African flora are surprised that common herbaceous savanna species have not yet been recorded in Gabon Grassy formations in Central Africa are perceived to contain only widespread species, which has led botanists to devote less time to inventories of savannas, sometimes only spending a single day in the field and using the literature to supplement their collec-
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