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At best, conservation decisions can only be made using the data available at the time. For plants and especially in the tropics, natural history collections remain the best available baseline information upon which to base conservation assessments, in spite of well-documented limitations in their taxonomic, geographic, and temporal coverage. We explore the extent to which changes to the plant biological record over 20 years have changed our conception of the conservation importance of 931 plant taxa, and 114 vegetation samples, recorded in forest reserves of the southwest Ghana biodiversity hotspot. 36% of species-level assessments changed as a result of new distribution data. 12% of species accepted in 2016 had no assessment in 1996: of those, 20% are new species publications, 60% are new records for SW Ghana, and 20% are taxonomic resolutions. Apparent species ranges have increased over time as new records are made, but new species publications are overwhelmingly of globally rare species, keeping the balance of perceived rarity in the flora constant over 20 years. Thus, in spite of considerable flux at the species record level, range size rarity scores calculated for 114 vegetation samples of the reserves in 1996 and 2016 are highly correlated with each other: r(112) = 0.84, p

Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species, based on two plastid barcoding genes, matK (incl. trnK) and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful for investigating different broad scale research questions in ecological and evolutionary biology., info:eu-repo/semantics/published

Degradation, a reduction of the ecosystem’s capacity to supply goods and services, is widespread in tropical forests and mainly caused by human disturbance. To maintain the full range of forest ecosystem services and support the development of effective conservation policies, we must understand the overall impact of degradation on different forest resources. This research investigates the response to disturbance of forest structure using several indicators: soil carbon content, arboreal richness and biodiversity, functional composition (guild and wood density), and productivity. We drew upon large field and remote sensing datasets from different forest types in Ghana, characterized by varied protection status, to investigate impacts of selective logging, and of illegal land use and resources extraction, which are the main disturbance causes in West Africa. Results indicate that functional composition and the overall number of species are less affected by degradation, while forest structure, soil carbon content and species abundance are seriously impacted, with resources distribution reflecting the protection level of the areas. Remote sensing analysis showed an increase in productivity in the last three decades, with higher resiliency to change in drier forest types, and stronger productivity correlation with solar radiation in the short dry season. The study region is affected by growing anthropogenic pressure on natural resources and by an increased climate variability: possible interactions of disturbance with climate are also discussed, together with the urgency to reduce degradation in order to preserve the full range of ecosystem functions.

Background and aims – Botanical surveys in Ghana yielded numerous new species, including saplings of what proved to be a tall, canopy tree. After several years, adults with flowers and fruits were found. Key results – Synsepalum ntimii, a new species similar to S. afzelii, is described and its affinities are discussed. Conservation status – Upper Guinea is fairly well surveyed compared to many other tropical regions, and the species has a limited range, so it is classified as Endangered in the IUCN system, even though recent surveys have extended the known range of S. ntimii to SE Liberia. It is locally rare, and much of the known Liberian range will be subject to mining operations.

We designed 3 image-based field guides to tropical forest plant species in Ghana, Grenada, and Cameroon and tested them with 1095 local residents and 20 botanists in the United Kingdom. We compared users’ identification accuracy with different image formats, including drawings, specimen photos, living plant photos, and paintings. We compared users’ accuracy with the guides to their accuracy with only their prior knowledge of the flora. We asked respondents to score each format for usability, beauty, and how much they would pay for it. Prior knowledge of plant names was generally low (

We evaluated the relative importance of annual rainfall, temperature and their seasonality to tree species distribution in Ghana. We used species presence/absence data from 2505 1-ha plots systematically distributed over Ghana's forests. Logistic regression was used to determine species responses to four climatic variables generated from the Worldclim database. The distribution of 95% of 20 species was significantly associated with annual rainfall, 60% with rainfall seasonality, 45% with isothermality and 40% with temperature seasonality. Annual rainfall explained on average most of the variation (17%, range = 0.5–52%) in species distribution, followed by rainfall seasonality 5% (range = 0.5–27%), isothermality 4% (range = 0.8–24%) and temperature seasonality 1% (range = 0.4–4.5%). Our results suggest that, out of the climatic variables investigated, rainfall is the main factor determining tree species distribution in Ghana; temperature also influences the distribution of a number of species, although it explains much less of the variation. The reduction in annual rainfall that prevailing climate-change scenarios predict for the region will result in a shift in the distribution of most species, whereas the predicted increase in temperature variation is likely to have little effect.

Summary. Six new species of Pavetta L. are described from the Wet Evergreen forests of Ghana, Ivory Coast and Liberia: Pavetta sonjae, P. bomiensis, P. abujuamii, P. ankasensis, P. quasidigita and P. sapoensis, the first of these with ornamental potential. The last three are considered ‘litter-bin’ species, a morphological syndrome whereby forest understorey plants accumulate litter in their leaf axils. Certain venation patterns are defined precisely and used to delimit species. The six new species are illustrated, compared with similar species and their conservation status is evaluated.

Regeneration Ecology of the Useful Flora of the Putu Range Rainforest, Liberia. We test the hypothesis that useful plants in general, and medicines in particular, are more likely to be pioneer and herbaceous species than any other guild or habit, using data from six communities in southeastern Liberia. Of 624 surveyed species from seven locally defined vegetation classes, 228 species (36 %) were found to be useful in the categories of food, medicine, materials, and social use. Five habits account for 98 % of surveyed species: Trees, treelets (including two palm species), lianes (including root climbers), shrubs, and herbs. Four guilds account for 93 % of the surveyed species: Swamp, shade–bearer, pioneer, and non–pioneer light demander (NPLD) species. A significantly higher proportion of pioneers is found to be useful overall (55 %) and useful medicinally (69 %) than for any other guild. However, the shade–bearing guild provides the greatest number of useful species (92 species) and the greatest number of medicinal species (55 species). Fifteen species were shortlisted by the communities for their particular importance, of which only one is a pioneer species. A similar proportion of species of each habit (about one–third of species) was found to be useful overall. In the case of medicinal use in particular, a significantly larger proportion of herbs (63 %) is medicinal than for any other habit. Our study from West Africa supports the findings of others working in the neotropics that disturbed and secondary vegetation classes are important sources of useful plants, particularly medicines. However, the greatest number of useful species are shade–bearing, which are most abundant in primary forest. Familiarity with and accessibility of old–growth forests to the communities of our study site due to Liberia’s recent history is likely responsible for their usefulness.

Summary Identifying areas of high biodiversity is an established way to prioritize areas for conservation [1–3], but global approaches have been criticized for failing to render global biodiversity value at a scale suitable for local management [4–6]. We assembled 3.1 million species distribution records for 40,401 vascular plant species of tropical Africa from sources including plot data, herbarium databases, checklists, and the Global Biodiversity Information Facility (GBIF) and cleaned the records for geographic accuracy and taxonomic consistency. We summarized the global ranges of tropical African plant species into four weighted categories of global rarity called Stars. We applied the Star weights to summaries of species distribution data at fine resolutions to map the bioquality (range-restricted global endemism) of areas [7]. We generated confidence intervals around bioquality scores to account for the remaining uncertainty in the species inventory. We confirm the broad significance of the Horn of Africa, Guinean forests, coastal forests of East Africa, and Afromontane regions for plant biodiversity but also reveal the variation in bioquality within these broad regions and others, particularly at local scales. Our framework offers practitioners a quantitative, scalable, and replicable approach for measuring the irreplaceability of particular local areas for global biodiversity conservation and comparing those areas within their global and regional context.

Although the publication of the vascular flora of the Caribbean islands of Trinidad and Tobago extended from 1928–1992, it is incomplete with the family Poaceae still outstanding. Many of the early recorded families are in need of extensive revision. Therefore, this checklist is intended to fill these gaps by providing a comprehensive list of the vascular plants for the islands. We compiled the checklist using the results from herbarium records, literature citations, online resources and a Rapid Botanic Survey (RBS) of 240 sample plots across the islands. From the RBS plots 22,500 vascular plant specimens were collected, yielding 1530 species. The herbarium records, literature citations and the RBS plots yielded a total of 3639 species, of which 2407 are indigenous, 1222 are exotic and 108 are endemic or near endemic. The low endemism is attributed to the islands’ close proximity to and recent separation from the South American continent. A total of 262 species of grasses (Poaceae) is published here for the first time along with the results from the RBS plots. Our annotated checklist further presents two types of conservation rating: the International Union for the Conservation of Nature Red List Categories and a global Star rating system. Based on the clustering of the ‘Star rating’ of each species, plant communities in the following areas: the Heights of Aripo, parts of the Nariva Swamp and the North-west Islands were identified as ‘hot spots’ of high conservation value which should continue to, or receive greater protection in the National Parks and Protected Areas system established in Trinidad and Tobago.

To answer new scientific and ecological questions and monitor multiple forest changes, a fine scale characterization of these ecosystems is needed, and could imply the mapping of specific species, of detailed forest types, and of functional composition. This characterization can be now provided by the novel Earth Observation tools. This study aims to contribute to understanding the innovation in forest and ecological research that can be brought in by advanced remote sensing instruments, and proposes the guild mapping approach as a tool to efficiently monitor the varied tropical forest resources. We evaluated, in tropical Ghanaian forests, the ability of airborne hyperspectral and simulated multispectral Sentinel-2 data, and derived vegetation indices and textures, to: distinguish between two different forest types; to discriminate among selected dominant species; and to separate trees species grouped according to their functional guilds: Pioneer, Non Pioneer Light Demanding, and Shade Bearer. We then produced guild classification maps for each area using hyperspectral data. Our results showed that with both hyperspectral and simulated Sentinel-2 data these discrimination tasks can be successfully accomplished. Results also stressed the importance of texture features, especially if using the lower spectral and spatial Sentinel-2 resolution data, and highlighted the important role of the new Sentinel-2 data for ecological monitoring. Classification results showed a statistically significant improvement in overall accuracy using Support Vector Machine, over Maximum Likelihood approach. We proposed the functional guilds mapping as an innovative approach to: (i) monitor compositional changes, especially with respect to the effects of global climate change on forests, and particularly in the tropical biome where the occurrence of hundreds of species prevents mapping activities at species level; (ii) support large-scale forest inventories. The imminent Sentinel-2 data could serve to open the road for the development of new concepts and methods in forestry and ecological research.

We analyse data from 12 permanent sample plots (PSPs) in Ghana to determine recovery rates of skid trails and gaps in forest logged 10–30 years previously. We examine four key indicators of recovery – basal area, mortality rate, diameter increment and changes in the balance of tree guilds (Pioneer Index) – to compare the forest directly affected by logging (the apparent extraction network, AEN), with adjacent, less damaged forest. Data are presented on gaps created by felling individuals of different species and diameter, with a view to refining existing yield allocation procedures. Our results indicate that forest recovery is slower than predicted by commonly used yield models. The basal area of AEN forest is below 23 m 2 ha −1 in all 12 plots, even 30 years after logging, and is not obviously increasing. Initially elevated annual mortality rates return to normal rates of less than 2% after 15 years in the non-AEN forest, and after 22 years in the AEN forest. Diameter increments peak early for pioneers, and increase linearly for shade-bearers across the 10–30 year period, but are not translated into gains in basal area. Only in one plot does the Pioneer Index of the AEN approach that of the less disturbed surrounding forest, implying inertia against canopy closure, as pioneers replace pioneers. We conclude that Ghana’s commercial logging practices are not sustainable on the current 40-year felling cycle. A different approach is required to achieve a sustainable harvest. Yield models will need to account for reduced site productivity. We suggest improved yield allocation through: (i) the development and use of electronic stock-maps to plan yield allocation, and as a basis for monitoring, (ii) accounting for species–specific differences, and (iii) collecting further data on the varied productivity of old extraction routes. Future studies should try to relate soil type to logging-impacts and recovery.

Gilbertiodendron tonkolili Burgt & Estrella sp. nov. (Leguminosae–Caesalpinioideae) is described and illustrated. The new species is endemic to a small area in central Sierra Leone. Gilbertiodendron tonkolili is characterised by leaves bearing 4–6 pairs of leaflets; stipules comprising a lower auriculate and an upper linear part, cream–white coloured bracteoles and a pale yellow adaxial petal. The fruits have a single longitudinal vein (sometimes a second partial vein). We assess G. tonkolili here as ‘Critically Endangered’ (CR) under the 2001 criteria of IUCN. We judge it to be morphologically closest to G. bilineatum which we confirm here as ‘Vulnerable’ (VU) and for which we also provide a full description and an illustration. A table of characters useful in differentiating the two species is given and a distribution map of both species is included.

Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns in tropical rain forest, West Africa and Atlantic Central Africa.

Plant morphological and physiological traits affect the way plants tolerate environmental stresses and therefore play an important role in shaping species distribution patterns in relation to environmental gradients. Despite our growing knowledge on the role of functional traits in structuring plant communities, few studies have tested their importance at large scales in the wet tropics. Here, we describe the distribution patterns of the most important West African rain forest timber species along the regional rainfall gradient and relate them to their functional traits. We found that the distribution patterns of 25 out of the 31 studied species (80%) were significantly related to mean annual rainfall. Shade tolerance and drought resistance were identified as the main strategy axes of variation. Wood density and leaf deciduousness emerged as the best predictor traits of species position along the rainfall gradient, explaining respectively 32 and 15 percent of the variation. Species traits tended to show stronger relationships with estimated optimum annual rainfall for each species than to the extreme rainfall conditions where they occur. The significant role of rainfall in shaping timber species distribution and the strong relationships between species traits and rainfall indicate that changes in climate, especially declining rainfall, could have strong effects on species composition and abundance in these tropical forests

Numerous linear taxon sequences can be generated from large phylogenetic trees raising questions about what criteria should be used to select an optimal sequence for collections of specimens and published taxonomic outputs including field guides. Possible criteria and ways to implement them are discussed in relation to the sequence ofAngiosperm families proposed by Haston & al. (2007). We define a particular spatial arrangement in one or more dimensions of the terminal nodes of a tree as a projection of that tree; a projection method is the set of rules by which the projection is achieved. We show that the projection of the Angiosperm phylogeny to a linear sequence, proposed by Haston & al. (2007), is not ideal because it is incompletely optimized for incompletely specified criteria. Tree projection methods that promote stability and incorporation of morphological data used in herbaria and other identification guides are proposed.

The diversity and structure of communities are partly determined by how species partition resource gradients. Plant size is an important indicator of species position along the vertical light gradient in the vegetation. 2. Here, we compared the size distribution of tree species in 44 Ghanaian tropical forest communities, using data from 880 one-hectare plots and over 118 000 trees belonging to more than 210 species. 3. The size distribution of forest species showed a continuous normal or log-normal distribution, with many canopy species and a few large species, and varied from community to community. Multiple regression showed that this variation is related to rainfall and to disturbance. 4. Size distributions in wet forests were less skewed than those in dry forests, with a smaller proportion of big species and a smaller size range. At the same time they exhibited tighter species packing, resulting in higher species richness. Communities with high disturbance have less species packing and lower species richness. 5. Synthesis. We conclude that the factors that constrain organism size and species coexistence in these tropical forest tree communities differ from those known to operate on a number of well-studied animal communities.

The potential of the dry zone agro-ecosystem of southern Honduras to contribute to the conservation of Mesoamerican dry forest tree diversity is evaluated. Four rural communities containing eight land uses were surveyed using rapid botanical sampling resulting in the identification of 241 tree and shrub species. As a result of ordination analysis, it is concluded that the land uses are relatively similar in their species composition, particularly maize fields (milpas), fallows, pastures and woodlots, because of the predominance of natural regeneration. Therefore all land uses might contribute to local tree diversity conservation. Those land uses in which planting also contributes to diversity, home gardens (solares) and orchards, are more distinct; however the tree species found there are widespread and often exotics and thus not the usual focus of conservation measures. Across the landscape the total complement of species considered a global priority for biodiversity conservation is very low and therefore this agro-ecosystem does not represent a good place in which to implement dry forest tree diversity conservation programmes. Instead its value is likely to be in the contribution that tree diversity makes to rural livelihoods. Particular consideration is given to Swietenia humilis Zucc. (small leaved mahogany) and its status as a threatened species is questioned because of its abundance within this landscape and its wide distribution.

The intermediate disturbance hypothesis (IDH) predicts local species diversity to be maximal at an intermediate level of disturbance. Developed to explain species maintenance and diversity patterns in species-rich ecosystems such as tropical forests, tests of IDH in tropical forest remain scarce, small-scale and contentious. We use an unprecedented large-scale dataset (2504 one-hectare plots and 331,567 trees) to examine whether IDH explains tree diversity variation within wet, moist and dry tropical forests, and we analyse the underlying mechanism by determining responses within functional species groups. We find that disturbance explains more variation in diversity of dry than wet tropical forests. Pioneer species numbers increase with disturbance, shade-tolerant species decrease and intermediate species are indifferent. While diversity indeed peaks at intermediate disturbance levels little variation is explained outside dry forests, and disturbance is less important for species richness patterns in wet tropical rain forests than previously thought.

Today, optical-fiber systems are used in the oilfield for sensing and telemetry applications. The most commonly used downhole is the distributed temperature sensing (DTS) system which collects permanent real-time temperature well logs. These logs are extremely useful for real-time production allocation, heavy oil thermal recovery (e.g., steam-assisted gravity drainage, SAGD), steam-well management, and well-integrity monitoring. Unfortunately, optical fibers are not immune to degradation under downhole conditions. Hydrogen, present in the wells because of corrosion or other factors, can attack the optical-fiber components causing attenuation increase. This attenuation can have a negative effect on the performance of the system, such as decreasing accuracy or resolution. Understanding the process and the impact of this degradation is of great importance to the reliable operation of these optical-fiber systems. This article shows how a combination of controlled testing and modeling calculations can be used to provide an estimation of the attenuation increase expected from the fiber with time and downhole conditions. Test results for attenuation of optical fiber in hydrogen atmospheres and under downhole temperatures will be shown. The article also provides results from the testing of a new optical fiber that was designed to give a considerable improvement in resistance to hydrogen attack. These results give an order of magnitude improvement in comparison with commercially available optical fibers. Early field tests are consistent with the results of the study.

1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree alpha-diversity of small rain forest plots in Africa and in Amazonia and climatic variables, to test the explanatory power of climate and the consistency of relationships between the two continents. 2. Our analysis included 1003 African plots and 512 Amazonian plots. All are located in old-growth primary non-flooded forest under 900 m altitude. Tree alpha-diversity is estimated using Fisher's alpha calculated for trees with diameter at breast height >= 10 cm. Mean diversity values are lower in Africa by a factor of two. 3. Climate-diversity analyses are based on data aggregated for grid cells of 2.5 x 2.5 km. The highest Fisher's alpha values are found in Amazonian forests with no climatic analogue in our African data set. When the analysis is restricted to pixels of directly comparable climate, the mean diversity of African forests is still much lower than that in Amazonia. Only in regions of low mean annual rainfall and temperature is mean diversity in African forests comparable with, or superior to, the diversity in Amazonia. 4. The climatic variables best correlated with the tree alpha-diversity are largely different in the African and Amazonian data, or correlate with African and Amazonian diversity in opposite directions. 5. These differences in the relationship between local/landscape-scale alpha-diversity and climate variables between the two continents point to the possible significance of an array of factors including: macro-scale climate differences between the two regions, overall size of the respective species pools, past climate variation, other forms of long-term and short-term environmental variation, and edaphics. We speculate that the lower alpha-diversity of African lowland rain forests reported here may be in part a function of the smaller regional species pool of tree species adapted to warm, wet conditions. 6. Our results point to the importance of controlling for variation in plot size and for gross differences in regional climates when undertaking comparative analyses between regions of how local diversity of forest varies in relation to other putative controlling factors.

1 Competition for light is a central issue in ecological questions concerning forest tree differentiation and diversity. Here, using 213 106 individual stem records derived from a national survey in Ghana, West Africa, we examine the relationship between relative crown exposure, ontogeny and phylogeny for 109 canopy species. 2 We use a generalized linear model (GLM) framework to allow interspecific comparisons of crown exposure that control for stem-size. For each species, a multinomial response model is used to describe the probabilities of the relative canopy illumination classes as a function of stem diameter. 3 In general, and for all larger stems, canopy-exposure increases with diameter. Five species have size-related exposure patterns that reveal local minima above 5 cm d.b.h., but only one, Panda oleosa, shows a local maximum at a low diameter. 4 The pattern of species exposures at 10 cm diameter is consistent with two overlapping groups, of which the smaller (21 species, including most pioneers) is generally better exposed. 5 Relative illumination rankings amongst species are significantly maintained over a wide range of stem sizes. Species that are well exposed at small diameters are therefore also more likely to be well exposed at larger diameters, although two species in the most exposed 25% of species at 10 cm d.b.h. drop to the lowest illumination quartile at 40 cm d.b.h., and three demonstrate the opposite (low-to-high) pattern. 6 Species capable of achieving the largest diameters are generally recorded less frequently in shade than are smaller species, even when compared as saplings, suggesting that species achieving large mature sizes are generally shade intolerant when small. Controlling for phylogeny reveals that this relationship holds across independent lineages. 7 We also find evidence that the range of strategies encountered is influenced by disturbance regimes. 8 We interpret our results as indicating a continuum of strategies that reflect an evolutionary trade-off between a species' mature size and its general shade-tolerance, in combination with differentiation based on disturbance based opportunities. Species that appear similar can therefore remain ecologically distinct over their lifetimes. © 2006 British Ecological Society.

Tropical dry forests, with their distinct and economically important diversity, are acknowledged conservation priorities because of alarming rates of forest conversion. Whilst it is realised that terrestrial conservation requires an understanding of landscape level patterns of diversity, forests are rarely assessed accordingly. Here we demonstrate that, in the case of the seasonally dry tropical forests of the Pacific watershed of Mesoamerica, landscape level assessment of woody diversity can inform decision making relevant to both between-landscape and within-landscape prioritisation. We report floristic surveys of dry forest landscapes in Oaxaca, Mexico and southern Honduras. It is noted that these forests are floristically similar to other seasonally dry tropical forests in the neotropics. By calculation of Genetic Heat Indices, a relative measure of the concentration of restricted range species in a sample, we determine that the conservation of the tree diversity of the coastal lowlands of Oaxaca should be prioritised over that of southern Honduras. The current conservation status of forested areas in Oaxaca is briefly described. We suggest that the greater degree of anthropogenic disturbance in southern Honduras may explain the relative lack of restricted range species there. We argue that some forest fallows can act as analogues of mature forest and therefore landscape elements other than mature forest need to be included in forest conservation assessments. We conclude that diversity sampling of any forest type should not be limited to mature forests, but extended to other elements of forested landscapes. # 2003 Elsevier Ltd. All rights reserved.

The forest belt in Upper Guinea stretches over 2000 km from Senegal in the west to Togo in the east. In this chapter a vegetation map is presented for the whole upper region

Elephant populations have declined greatly in the rain forests of Upper Guinea (Africa, west of the Dahomey Gap). Elephants have a number of well-known influences on vegetation, both detrimental and beneficial to trees. They are dispersers of a large number of woody forest species, giving rise to concerns that without elephants the plant diversity of Upper Guinean forest plant communities will not be maintained. This prospect was examined with respect to four sources of inventory and research data from Ghana, covering nearly all (more than 2000) species of forest plant. Evidence supporting the hypothesis that plant populations are collapsing without elephants is conspicuously absent in these datasets, although Balanites wilsoniana is likely to suffer dramatically on a centennial scale in the absence of forest elephants. A few other species are likely to decline, although at an even slower rate. In the context of other processes current in these forests, loss of elephants is an insignificant concern for plant biodiversity. Elephant damage of forests can be very significant in Africa, but loss of this influence is more than compensated for by human disturbance. Elephants have played a significant part in the shaping of West African rain forest vegetation. However, it is the conservation of elephants that should be of primary concern. Tree populations should be managed to promote them, rather than vice versa.

The results described are of the effects of fire exclusion since 1957 on a small area of savanna close to the forest-zone boundary, on the northern Accra Plains, Ghana. A forest thicket has developed, with forest species in intimate association with nonforest species. The forest component includes healthy regeneration of the important timber species, Milicia (= Chlorophora) excelsa (Benth. & Hook.) Berg (nomenclature follows Hutchinson & Dalziel [1954-721 except where authorities are given) (max. 114 cm gbh) and Antiaris toxicaria Lesch. (53 cm gbh). Ceiba pentandra is the largest and most abundant canopy tree, with a maximum girth of 2 m (height 22 m). Other large trees were Albiziaferruginea (137 cm gbh) and the remnant savanna trees Lonchocarpus sericeus (74 cm gbh) and the naturalized exotic Azadirachta indica (99 cm gbh). AFRICAN GUINEA SAVANNAS owe their distinctive physiognomy to frequent ground fires, and only to a lesser extent to the effects of climate and grazing. At one time it was proposed that, without fire, the savannas of West Africa would have supported forest vegetation, and that savanna was therefore the result of human activity. This view is not generally accepted now largely because humans have been a natural biotic influence on vegetation development in Africa for many millennia. Nevertheless, it is clear from several studies that, if savanna is protected from fire, trees become more abundant (Trapnell 1959, Charter & Keay 1960, Mensbruge & Bergeroo-Campagne 1961, Brookman-Amissah et al. 1980, Chidumayo 1988). In 1957, R. Rose-Innes (pers. comm.) established a fenced rectangular plot slightly larger than one acre (about 0.5 ha) in an area of savanna in the northeast corner (0?04'E, 6?08'N) of the Accra Plains in SE Ghana. Woody plants at the time were no more than 3-4 m tall. The plot has since been protected from fire and grazing by the staff of the University of Ghana Agricultural Research Station at Kpong (ARS), on whose land the plot is located. The fence is now (1989) partly in disrepair, and fire has encroached on part of the plot in recent years. No proper control sample of the savanna vegetation in the area was kept, but the surrounding land has been regularly burned and grazed since the exclosure was established. The exclosure is on flat ground, and the soil is a tropical black earth (vertisol). Outside the exclosure, the savanna vegetation at Kpong is a fairly typical Guinea Savanna (Jenik & Hall 1976) with short, scattered trees up to about 6 m tall, and a continuous cover of grasses. This savanna area is within, but close to the western limit of the "Dahomey gap," the phytogeographical boundary between the forests of Upper Guinea to the west and those of Lower Guinea to the east (see Hall & Swaine 1981). The tree species are characteristic of savanna over a wide area of West Africa. Tree species recorded in a small sample in 1979 are listed in Table 1. Because the Lonchocarpus is so successful in these coastal savannas it will be referred to as a "savanna tree" in this paper, even though in some areas it is found also in forest. The grouping of species into "forest" or "savanna" species is based on relative abundance of the species in the two vegetation types as perceived by the authors and could be misleading, except that our conclusions do not depend on the distinction.