Central African Rainforest Research Articles

Origin and history of the Dahomey Gap separating West and Central African rain forests: insights from the phylogeography of the legume tree Distemonanthus benthamianus

AbstractAimThe aim of this study was to understand the origin of the forest flora currently found in the Dahomey Gap (DG), a 200‐km‐wide forest‐savanna mosaic separating the West African and Central African rain forest blocks. More specifically, using a widespread rain forest tree species, Distemonanthus benthamianus (Fabaceae), we will test the hypothesis that the DG populations are remnants of a population dating back from the African Humid Period of the Holocene, when West African and Central African rain forests were supposedly connected.LocationTropical forests of Upper Guinea (West Africa) and Lower Guinea (Atlantic Central Africa) and the forest‐savanna mosaic of the DG extending from eastern Ghana to Benin.MethodsFour hundred and twenty‐nine D. benthamianus samples from West to Central Africa were genotyped with 11 nuclear microsatellite markers. After detecting geographically coherent gene pools, their genetic diversity and differentiation were estimated and their demographic histories were inferred using coalescent simulations and approximate Bayesian computation (ABC) tests.ResultsFive parapatric gene pools were identified: three in Lower Guinea, one in Upper Guinea and one in the DG. ABC tests indicate that the DG gene pool probably originates from the admixture of adjacent Upper and Lower Guinean gene pools, with a higher contribution from Upper Guinea, at a timeframe consistent with the early Holocene (around 13–7 ka). The lower genetic diversity documented in the DG could result from a founder effect and/or from a demographic decline consistent with the Holocene climatic pejoration documented around 3 ka.Main conclusionsThis phylogeographical study inferring the history of the DG populations of D. benthamianus is consistent with palaeovegetation data that suggest that the forest flora of the DG might be essentially relicts of the early Holocene period when the Guineo‐Congolian forest reached its maximum geographical distribution.

Limitation of seedling growth by potassium and magnesium supply for two ectomycorrhizal tree species of a Central African rain forest and its implication for their recruitment.

In the ectomycorrhizal caesalpiniaceous groves of southern Korup National Park, the dominant tree species, Microberlinia bisulcata, displays very poor insitu recruitment compared with its codominant, Tetraberlinia bifoliolata. The reported ex situ experiment tested whether availabilities of soil potassium and magnesium play a role. Seedlings of the two species received applications of K and Mg fertilizer in potted native soil in a local shade house, and their responses in terms of growth and nutrient concentrations were recorded over 2years. Amended soil concentrations were also determined. Microberlinia responded strongly and positively in its growth to Mg, but less to K; Tetraberlinia responded weakly to both. Added Mg led to strongly increased Mg concentration for Microberlinia while added K changed that concentration only slightly; Tetraberlinia strongly increased its concentration of K with added K, but only somewhat its Mg concentration with added Mg. Additions of Mg and K had small but important antagonistic effects. Microberlinia is Mg-demanding and apparently Mg-limited in Korup soil; Tetraberlinia, whilst K-demanding, appeared not to be K-limited (for growth). Added K enhanced plant P concentrations of both species. Extra applied Mg may also be alleviating soil aluminum toxicity, and hence improving growth indirectly and especially to the benefit of Microberlinia. Mg appears to be essential for Microberlinia seedling growth and its low soil availability in grove soils at Korup may be an important contributing factor to its poor recruitment. Microberlinia is highly shade-intolerant and strongly light-responding, whilst Tetraberlinia is more shade-tolerant and moderately light-responding, which affords an interesting contrast with respect to their differing responses to Mg supply. The study revealed novel aspects of functional traits and likely niche-partitioning among ectomycorrhizal caesalps in African rain forests. Identifying the direct and interacting indirect effects of essential elements on tropical tree seedling growth presents a considerable challenge due the complex nexus of causes involved.

On Intensive Late Holocene Iron Mining and Production in the Northern Congo Basin and the Environmental Consequences Associated with Metallurgy in Central Africa.

An ongoing question in paleoenvironmental reconstructions of the central African rainforest concerns the role that prehistoric metallurgy played in shaping forest vegetation. Here we report evidence of intensive iron-ore mining and smelting in forested regions of the northern Congo Basin dating to the late Holocene. Volumetric estimates on extracted iron-ore and associated slag mounds from prehistoric sites in the southern Central African Republic suggest large-scale iron production on par with other archaeological and historically-known iron fabrication areas. These data document the first evidence of intensive iron mining and production spanning approximately 90 years prior to colonial occupation (circa AD 1889) and during an interval of time that is poorly represented in the archaeological record. Additional site areas pre-dating these remains by 3-4 centuries reflect an earlier period of iron production on a smaller scale. Microbotanical evidence from a sediment core collected from an adjacent riparian trap shows a reduction in shade-demanding trees in concert with an increase in light-demanding species spanning the time interval associated with iron intensification. This shift occurs during the same time interval when many portions of the Central African witnessed forest transgressions associated with a return to moister and more humid conditions beginning 500-100 years ago. Although data presented here do not demonstrate that iron smelting activities caused widespread vegetation change in Central Africa, we argue that intense mining and smelting can have localized and potentially regional impacts on vegetation communities. These data further demonstrate the high value of pairing archeological and paleoenvironmental analyses to reconstruct regional-scale forest histories.

Two new species of long-fingered frogs of the genus Cardioglossa (Anura: Arthroleptidae) from Central African rainforests

We describe two new frog species of Cardioglossa (Family Arthroleptidae) from Central Africa. The new species are found in the rainforests of western-central Democratic Republic of the Congo and the Republic of the Congo near the Gabonese border, respectively. We demonstrate that these species are morphologically and genetically distinct from each other and all other species of Cardioglossa. Both new species lack the dorsal hour-glass pattern present in many species of the genus, but they can be distinguished from each other and related species by distinctive colour patterns on their lateral surfaces and extremities. Both new species most closely resemble C. gratiosa, which occurs in the Atlantic coastal forests extending from Cameroon through Gabon. The new species can be differentiated from C. gratiosa by the absence of black transverse bars on all limbs or by distinctive lateral colouration. Analysis of mitochondrial ribosomal 16S DNA sequences reveals low to moderate levels (1.9–7.5%) of divergence between these new species and closely related species of Cardioglossa. The floodplains of the Congo and Ubangi Rivers may be important geographic barriers for many of these species. The occurrence of these two new lowland species in the Congo Basin reveals that the distribution and diversity of Cardioglossa in this region was underestimated. In addition, we elevate C. nigromaculata inornata to species-level status, based in part on newly available colour photographs from 1950 of specimens from the only known locality.

Jonathan Kingdon and the East African Forests

Jonathan Kingdon, 45 years ago, first pointed out the special nature of the East African coastal and montane forests, that a number of mammals are endemic to these forests, and that they are not just an eastern extension of the Central African rainforest belt. Other authors, and Kingdon himself, subsequently enhanced and modified this concept (which applies also to other animals and to plants) although, in the main, the montane forms have been designated to the ‘Eastern Arc’ region or subregion and the coastal ones to the ‘Swahilian’ region or subregion. In this paper, I review the mammals of these two sets of forests, and find that they are not in fact so different from each other. As such, I formally propose to unite them, using the name under which Kingdon informally designated them, the ‘Zanj Subregion’.

Human seroprevalence indicating hantavirus infections in tropical rainforests of Côte d'Ivoire and Democratic Republic of Congo.

Hantaviruses are members of the Bunyaviridae family carried by small mammals and causing human hemorrhagic fevers worldwide. In Western Africa, where a variety of hemorrhagic fever viruses occurs, indigenous hantaviruses have been molecularly found in animal reservoirs such as rodents, shrews, and bats since 2006. To investigate the human contact to hantaviruses carried by these hosts and to assess the public health relevance of hantaviruses for humans living in the tropical rainforest regions of Western and Central Africa, we performed a cross-sectional seroprevalence study in the region of Taï National Park in Côte d’Ivoire and the Bandundu region near the Salonga National Park in the Democratic Republic (DR) of Congo. Serum samples were initially screened with enzyme-linked immunosorbent assays using nucleoproteins of several hantaviruses as diagnostic antigens. Positive results were confirmed by Western blotting and immunofluorescence testing. Seroprevalence rates of 3.9% (27/687) and 2.4% (7/295), respectively, were found in the investigated regions in Côte d’Ivoire and the DR Congo. In Côte d’Ivoire, this value was significantly higher than the seroprevalence rates previously reported from the neighboring country Guinea as well as from South Africa. Our study indicates an exposure of humans to hantaviruses in West and Central African tropical rainforest areas. In order to pinpoint the possible existence and frequency of clinical disease caused by hantaviruses in this region of the world, systematic investigations of patients with fever and renal or respiratory symptoms are required.

Charcoal-inferred Holocene fire and vegetation history linked to drought periods in the Democratic Republic of Congo.

The impact of Holocene drought events on the presumably stable Central African rainforest remains largely unexplored, in particular the significance of fire. High-quality sedimentary archives are scarce, and palynological records mostly integrate over large regional scales subject to different fire regimes. Here, we demonstrate a direct temporal link between Holocene droughts, palaeofire and vegetation change within present-day Central African rainforest, using records of identified charcoal fragments extracted from soil in the southern Mayumbe forest (Democratic Republic of Congo). We find three distinct periods of local palaeofire occurrence: 7.8-6.8ka BP, 2.3-1.5ka BP, 0.8ka BP - present. These periods are linked to well-known Holocene drought anomalies: the 8.2ka BP event, the 3rd millennium BP rainforest crisis and the Mediaeval Climate Anomaly. During and after these Holocene droughts, the Central African rainforest landscape was characterized by a fragmented pattern with fire-prone open patches. Some fires occurred during the drought anomalies although most fires seem to lag behind them, which suggests that the open patches remained fire-prone after the actual climate anomalies. Charcoal identifications indicate that mature rainforest patches did persist through the Early to Mid-Holocene climatic transition, the subsequent Holocene thermal optimum and the third millennium BP rainforest crisis, until 0.8ka BP. However, disturbance and fragmentation were probably more prominent near the boundary of the southern Mayumbe forest. Furthermore, the dominance of pioneer and woodland savanna taxa in younger charcoal assemblages indicates that rainforest regeneration was hampered by increasingly severe drought conditions after 0.8ka BP. These results support the notion of a dynamic forest ecosystem at multicentury time scales across the Central African rainforest.

Tree roots can penetrate deeply in African semi-deciduous rain forests: evidence from two common soil types

Abstract:Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than the 95 cm depth previously reported in the literature for tropical rain forests. As sampling depth could explain this discrepancy, we recommend a sampling depth of at least 3–5 m to accurately estimate root distribution. The drier the dry season, the deeper the sampling depth should be. Our results are consistent with global models of root distribution in forest ecosystems, which are driven by climate variables. We thus suggest that deep rooting could be common in rain forests with a marked dry season.

Comparative phylogeography of eight herbs and lianas (Marantaceae) in central African rainforests.

Vegetation history in tropical Africa is still to date hardly known and the drivers of population differentiation and speciation processes are little documented. It has often been postulated that population fragmentations following climate changes have played a key role in shaping the geographic distribution patterns of genetic diversity and in driving speciation. Here we analyzed phylogeographic patterns (chloroplast-DNA sequences) within and between eight (sister) species of widespread rainforest herbs and lianas from four genera of Marantaceae (Halopegia, Haumania, Marantochloa, Megaphrynium), searching for concordant patterns across species and concordance with the Pleistocene refuge hypothesis. Using 1146 plastid DNA sequences sampled across African tropical lowland rainforest, particularly in the Lower Guinean (LG) phytogeographic region, we analyzed intra- and interspecific patterns of genetic diversity, endemism and distinctiveness. Intraspecific patterns of haplotype diversity were concordant among most species as well as with the species-level diversity pattern of Marantaceae. Highest values were found in the hilly areas of Cameroon and Gabon. However, the spatial distribution of endemic haplotypes, an indicator for refuge areas in general, was not congruent across species. Each proposed refuge exhibited high values of endemism for one or a few species indicating their potential role as area of retraction for the respective species only. Thus, evolutionary histories seem to be diverse across species. In fact, areas of high diversity might have been both refuge and/or crossing zone of recolonization routes i.e., secondary contact zone. We hypothesize that retraction of species into one or the other refuge happened by chance depending on the species' distribution range at the time of climate deterioration. The idiosyncratic patterns found in Marantaceae species are similar to those found among tropical tree species, especially in southern LG.

Adaptive, convergent origins of the pygmy phenotype in African rainforest hunter-gatherers.

The evolutionary history of the human pygmy phenotype (small body size), a characteristic of African and Southeast Asian rainforest hunter-gatherers, is largely unknown. Here we use a genome-wide admixture mapping analysis to identify 16 genomic regions that are significantly associated with the pygmy phenotype in the Batwa, a rainforest hunter-gatherer population from Uganda (east central Africa). The identified genomic regions have multiple attributes that provide supporting evidence of genuine association with the pygmy phenotype, including enrichments for SNPs previously associated with stature variation in Europeans and for genes with growth hormone receptor and regulation functions. To test adaptive evolutionary hypotheses, we computed the haplotype-based integrated haplotype score (iHS) statistic and the level of population differentiation (FST) between the Batwa and their agricultural neighbors, the Bakiga, for each genomic SNP. Both |iHS| and FST values were significantly higher for SNPs within the Batwa pygmy phenotype-associated regions than the remainder of the genome, a signature of polygenic adaptation. In contrast, when we expanded our analysis to include Baka rainforest hunter-gatherers from Cameroon and Gabon (west central Africa) and Nzebi and Nzime neighboring agriculturalists, we did not observe elevated |iHS| or FST values in these genomic regions. Together, these results suggest adaptive and at least partially convergent origins of the pygmy phenotype even within Africa, supporting the hypothesis that small body size confers a selective advantage for tropical rainforest hunter-gatherers but raising questions about the antiquity of this behavior.

Dietary habits of the Black-legged mongoose Bdeogale nigripes (Mammalia: Carnivora) in the rainforest of Southeastern Nigeria

The Black-legged mongoose Bdeogale nigripes is a poorly studied carnivore (family Herperstidae) found only in Central African rainforests. In Southeastern Nigeria, its known range is strictly limited to the localities close to the Cameroon border and just east of the Cross River. This article reports some original data on the diet of B. nigripes, the first objectively positive data on this species according to the analysis of their stomach contents. Moreover, these are the first data collected in Nigeria, including the first known record west of the Cross River. B. nigripes seems to be slowly expanding its range westward. Most of its prey were vertebrates, mainly mammals, followed by reptiles and birds. Invertebrate prey was also found, mainly insects, followed by centipedes. In terms of their frequency of occurrence, insects and other arthropods (50.48%) were consumed significantly more often than any other type of prey. Both arthropods (88.88%) and mammals (88.88%) were almost always present in the examined stomachs. Larger prey (mammals), such as Cricetomys emini (1.9% of the total number of prey) and Xerus erythropus (0.95%) were occasionally preyed upon, as well as small snakes (1.9%). Comparing these results with the limited information available thus far, it is evident that there are more prey taxa, in addition to food categories, than previously estimated, and overall this demonstrates that arthropods and mammals are the most commonly consumed prey, the first because they are certainly more numerous, while the latter are far more significant in terms of biomass. In fact, the analysis indicates that mammals (79.21%), and especially large rodents (59.23%), were the main contributors in terms of biomass. Conversely, small prey, in particular arthropods, some of which are tiny, are of decidedly low trophic significance (5.43%).

Impact of fine‐scale edaphic heterogeneity on tree species assembly in a central African rainforest

AbstractQuestionsSoil properties have been shown to partially explain tree species distribution in tropical forests. Locally, species turnover across space can result not only from edaphic heterogeneities but also from limited seed dispersal. To characterize the contribution of each process, contact areas between contrasted soil types offer ideal settings. In the present study, we aimed to test species and species assemblage responses to a sharp edaphic discontinuity in a tropical forest tree community.LocationYoko forest reserve (6975 ha), Democratic Republic of the Congo.MethodsWe set up four 500–600‐m long parallel transects crossing two contrasted edaphic habitats, one lying on clayey soil and the other on sandy soil. The canopy and subcanopy trees were identified and geo‐referenced along the transects over a width of 50 m and 5 m, respectively, and soil samples were collected every 50 m to characterize each habitat.ResultsCorrespondence analyses indicated a clear differentiation of tree communities between sandy and clayey soils. Using a torus‐translation method combined with Chi‐squared non‐parametric tests, we observed that ca. 40% and 18% of the species represented by at least 12 individuals displayed significant density differences according to habitat in the canopy and subcanopy, respectively, although very few species displayed significant differences in their relative abundance. Nevertheless, whole community tests of differentiation (in species relative abundances) between soil types were significant in both strata, even after removing individual species or families displaying a significant habitat preference.ConclusionWhile only a minority of species displayed a clear habitat preference, we still observed a community‐wide impact of the edaphic discontinuity on species assemblages at a local scale. Our results provide further evidence for the major contribution of environmental heterogeneity in maintaining biodiversity in tropical forests.

Plant mineral concentrations related to foraging preferences of western lowland gorilla in Central African forest clearings.

In the Central African rain forest, mineral resources essential to organisms are distributed heterogeneously. Forest clearings, locally known as bais, attract numerous species presumably due to the mineral richness of these sites, though understanding of the factors drawing species to bais remains speculative. Western lowland gorillas (Gorilla g. gorilla) selectively feed on particular plant species and parts within bais, but studies of such feeding preferences have focused on one site. Here, we compared concentrations of minerals and macronutrients from plants gorillas consumed and those they did not in 16 bais to gain inference regarding drivers of resource selection within bais and bai use. The availability of gorilla feeding plants varied between surveyed bais, with some consumed species occurring only at a few bais. Regardless of bai specific species composition, significantly higher concentrations of Na, K, and Ca were found in consumed plants, and other trace minerals were more common in consumed plants. In contrast, macronutrients appeared to play no major role in feeding plant selectivity with consumed species often having lower concentrations than non-consumed species. We found evidence for seasonal differences in Mg and Na concentrations, but the concentrations of other minerals in consumed plants were consistent across time. These findings provide insight to the drivers of bai visitation by gorillas. The high variation in species across bais may elicit use of multiple bais, but the general increased mineral composition of consumed species across bais suggests metabolic requirements may be met through consumption of a variety of species.

Influence of 1100 years of burning on the central African rainforest

Four major forest types are currently present in the central African rainforest; mixed forest, Marantaceae forest, monodominant Gilbertiodendron forest and swamp forest. These forest types span vast areas and demonstrate highly significant differences in diversity and productivity; yet factors responsible for their formation are poorly understood. One hypothesis is that they are as a consequence of different intensities of past human activity, in particular burning. Here we present results from fossil charcoal contained in 12 sediment cores spanning the last 2500 yr and covering a spatial area of more than 900 km2. These records demonstrate that burning started in the last 1100 yr with areas currently covered by Marantaceae forest undergoing more frequent burning events than the other forest types. In comparison monodominant Gilbertiodendron forest appear to have undergone large burning events only in the past 200 yr. These records also demonstrate a lack of spatial relationship between fire events at the different sites (discontinuous and asynchronous) suggesting that these fires resulted from localised burning events probably caused by human ignitions. Whilst the large spatial scale of past human activities in the South American rainforest is now widely acknowledged, these results indicate, for the first time, the significant impact that early human populations had on the community composition of central African rainforest.

Widespread decline of Congo rainforest greenness in the past decade.

Tropical forests are global epicentres of biodiversity and important modulators of climate change, and are mainly constrained by rainfall patterns. The severe short-term droughts that occurred recently in Amazonia have drawn attention to the vulnerability of tropical forests to climatic disturbances. The central African rainforests, the second-largest on Earth, have experienced a long-term drying trend whose impacts on vegetation dynamics remain mostly unknown because in situ observations are very limited. The Congolese forest, with its drier conditions and higher percentage of semi-evergreen trees, may be more tolerant to short-term rainfall reduction than are wetter tropical forests, but for a long-term drought there may be critical thresholds of water availability below which higher-biomass, closed-canopy forests transition to more open, lower-biomass forests. Here we present observational evidence for a widespread decline in forest greenness over the past decade based on analyses of satellite data (optical, thermal, microwave and gravity) from several independent sensors over the Congo basin. This decline in vegetation greenness, particularly in the northern Congolese forest, is generally consistent with decreases in rainfall, terrestrial water storage, water content in aboveground woody and leaf biomass, and the canopy backscatter anomaly caused by changes in structure and moisture in upper forest layers. It is also consistent with increases in photosynthetically active radiation and land surface temperature. These multiple lines of evidence indicate that this large-scale vegetation browning, or loss of photosynthetic capacity, may be partially attributable to the long-term drying trend. Our results suggest that a continued gradual decline of photosynthetic capacity and moisture content driven by the persistent drying trend could alter the composition and structure of the Congolese forest to favour the spread of drought-tolerant species.

Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century

Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century

Ancient origin of a rainforest in Gabon as revealed by carbon isotope data of vegetation and soil

Holocene climate change caused disturbances of the Central African rainforest belt, with decrease in forest area during drier conditions followed by expansion during wetter periods. Today, human impact is a driver for forest degradation in the Congo Basin. For assessing the quality and quantity of forest degradation, information on biodiversity and carbon stocks from reference ecosystems is needed which (1) were not affected by Holocene climate change and (2) lack direct human impacts like logging or shifting cultivation. The Birougou Mountains in Gabon, which were devoid of direct human impact over the last centuries, may resemble such a reference ecosystem. This paper tests the hypothesis that the Birougou Mountains served as refugium for rainforest vegetation during periods of Holocene climate change. For 34 forest plots within the Birougou Mountains and 27 savannah plots within an adjacent forest savannah mosaic, we present stable carbon isotope data from current vegetation cover, organic inputs to soil organic carbon (SOC), bulk SOC and the humic acid fraction of SOC. Additionally, we estimated the mean age of the SOC humic acid fraction by 14C dating. The data indicated a continuous forest cover in the Birougou Mountains since – at least – the Holocene climate optimum, but a change from forest to savannah vegetation in the forest savannah mosaic. Results confirm the forest of the Birougou Mountains as a refugium of rainforest vegetation and suitable reference for the natural potential regarding biodiversity and ecosystem carbon stocks.

Relationships between tree species diversity and above-ground biomass in Central African rainforests: implications for REDD

SUMMARYTropical forests are both important stores of carbon and among the most biodiverse ecosystems on the planet. Reducing emissions from deforestation and degradation (REDD) schemes are designed to mitigate the impacts of climate change, by conserving tropical forests threatened by deforestation or degradation. REDD schemes also have the potential to contribute significantly to biodiversity conservation efforts within tropical forests, however biodiversity conservation and carbon sequestration need to be aligned more closely for this potential to be realized. This paper analyses the relationship between tree species diversity and above-ground biomass (AGB) derived from 1-ha tree plots in Central African rainforests. There was a weakly significant correlation between tree biomass and tree species diversity (r = 0.21, p = 0.03), and a significantly higher mean species diversity in plots with larger AGB estimates (M = 44.38 species in the top eight plots, compared to M = 35.22 in the lower eight plots). In these Central African plots, the relationship between tree species diversity and AGB appeared to be highly variable; nonetheless, high species diversity may often be related to higher biomass and, in such cases, REDD schemes may enhance biodiversity by targeting species diverse forests.

Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century.

Humans have hunted wildlife in Central Africa for millennia. Today, however, many species are being rapidly extirpated and sanctuaries for wildlife are dwindling. Almost all Central Africa's forests are now accessible to hunters. Drastic declines of large mammals have been caused in the past 20 years by the commercial trade for meat or ivory. We review a growing body of empirical data which shows that trophic webs are significantly disrupted in the region, with knock-on effects for other ecological functions, including seed dispersal and forest regeneration. Plausible scenarios for land-use change indicate that increasing extraction pressure on Central African forests is likely to usher in new worker populations and to intensify the hunting impacts and trophic cascade disruption already in progress, unless serious efforts are made for hunting regulation. The profound ecological changes initiated by hunting will not mitigate and may even exacerbate the predicted effects of climate change for the region. We hypothesize that, in the near future, the trophic changes brought about by hunting will have a larger and more rapid impact on Central African rainforest structure and function than the direct impacts of climate change on the vegetation. Immediate hunting regulation is vital for the survival of the Central African rainforest ecosystem.

Artificial Germination Activation of Dialium corbisieri by Imitation of Ecological Process

Species of the gender Dialium commonly are trees found in Central African rainforests. They produce tasty sugary fruits, feeding numerous frugivores, but are, despite their valuable nutritional value, rarely exploited by humans. A potential reason for this could be the complexity of symbiotic dependence between trees and pollinators, germination activators, and dispersers causing problems in ancestral and contemporary domestication. We investigated Dialium corbisieri reproduction in the Democratic Republic of the Congo, Bandundu Province. Here we give a key for an artificial activation of germination of these trees ecologically adapted to the digestive system of their ape dispersers: By perforation of the impermeable seed coat protection, water assimilation and subsequent activation of germination becomes possible. By this nicking, pretreatment germination increases from 0 to 96%, representing an inexpensive and simple treatment to be used under natural conditions and in developing countries. The use of this mechanical activation for forest management, conservation, and economic use is discussed.