Search

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 (

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.

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.

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.

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.

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.

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

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.