Wooded Savannah Research Articles

Spatio-Temporal Dynamic of Land Use and Land Cover in the Classified Forest of Djoli-Kera, South-Eastern, Chad

This study was carried out in the classified forest of Djoli-Kera found in the South-Eastern part of Chad. It aimed to analyze the spatial and temporal dy-namics of land cover between 1972 and 2013 and to determine the drivers of vegetation degradation. The databases used were made up of 4 Landsat satellite images (1MSS of 1972, 5TM of 1984, 7ETM+ of 1990 and 2010) and a spot 6 image of 2013, supplemented by field studies. Satellite images were processed using ENVI and ArcGIS software. Interview was used to identify the activities carried out by the local population. In 1972, the classified forest consisted of four types of land cover, the most important of which was open forest (51%), followed by wooded savannah (26%), tree savannah (21%) and sparse vegetation consisting of farms and fallows (2%). Gradually open forest and tree savannah disappeared. In 2013, the main types of land cover were shrub savannah (40%), sparse vegetation (28%), wooded savannah (12%), bare soil (12%) and dwellings (8%). Livestock, agriculture, wood collection and bushfires are perceived by local population as main drivers of forest cover change. Awareness-raising, monitoring and regulation of access to resources must be pursued, but also managers of the classified forest must accompany the local populations in the planting of trees and the setting up of more efficient farming systems to reduce pressure on the forest’s resources.

<i>Saba senegalensis</i>: Key Features and Uses

Native of West Africa, Saba senegalensis belongs to the family of Apocynaceae, and is a wild plant that is mainly exploited in the diet. It grows mainly along riverbanks, in wooded savannah areas in humid areas, in gallery forests and in rocky ravines and hills. Saba senegalensis is a large woody liana with white latex, dark gray bark, can reach more than 40 m high and a trunk that can measure up to 47 cm in diameter. The fruit is a globose shell, 7 to 10 cm long, 6 to 8 cm wide. The leaves are opposite, elliptical, dark green in color, about 8 to 15 cm long and 4 to 6 cm wide. This fruit is characterized by its richness in antioxidant molecules especially vitamin C (480 mg/100 g) and total polyphenols (945.83 mg/100 g). The fruit contents 41.43 until 80% water with a low pH (2.24). In Senegal, the fruit is eaten as it or transformed into puree, nectar, syrup, canned etc. It is a plant that has enormous therapeutic virtues, from the fruit to the roots through the leaves, bark, and latex. Despite its high nutritional potential, its many therapeutic virtues and its economic potential, Saba senegalensis remains under-exploited. Further researches on the nutritional and therapeutic properties deserve to be conducted.

Conservation of chimpanzeesPan troglodytes verusand other primates depends on forest patches in a West African savannah landscape

AbstractHabitat loss and fragmentation, hunting pressure, and human–wildlife conflict threaten the survival of primates across Africa. Particularly dramatic forest losses have occurred outside protected areas in the Guinean forest–savannah transition zone. Using the Boé region, Guinea-Bissau, as a case study, we investigated whether and how this rapidly humanized mosaic of wooded savannah, gallery forests and cropland could sustain viable primate populations. We conducted line transect surveys and reconnaissance (recce) walks to assess populations of one Critically Endangered (chimpanzeePan troglodytes verus), one Endangered (Temminck's red colobusPiliocolobus badius temminckii), one Vulnerable (king colobusColobus polykomos), and one Near Threatened (sooty mangabeyCercocebus atys) arboreal primates across a 104 km2section of Boé in the dry season of 2016. Using the standing crop nest count method we estimated a relatively high chimpanzee density (0.77 individuals per km2, 95% CI 0.45–1.34). An assessment of habitat selection showed that chimpanzees prefer semi-dense forest and fallow fields with remnant old trees for nesting, and locations close to rivers. The other primates studied occurred in extremely low densities and were largely restricted to gallery forests. Our results indicate a need for immediate action to ensure the long-term survival of the primate community in the human-dominated landscape of Boé. Our recommendations include action to maintain hunting pressure at a low level, restoring and protecting gallery forests, introducing incentives for farmers for forest protection and primate-friendly practices, and extending the conservation programme to all arboreal primates in the region.

Analysis of Landscape Dynamics, Trend Indicators and Evolutionary Trends in the Rusizi National Park (Burundi) from 1980 to 2015 by Remote Sensing and Field Investigations

Nowadays, adaptive management of protected areas is lacking objective and integrated indicators for rigorous assessment of their evolutionary trends and the effectiveness of the conservation methods on the basis of conservation objectives and landscape dynamics. The study provides a methodological approach for determining trend indices and historical evolutionary trends which describe the developments of the Rusizi Park known to be the most threatened protected area in Burundi. The study is based on the diachronic analysis of land cover using multi-date Landsat images from 1984, 1990, 2011, 2000 and 2015 and field data. The supervised classification of the images made it possible to identify 9 to 10 land cover classes with contrasting evolutions. The park's matrix, which was made of wooded savannah in 1984 with 43.78%, consists of shrub savannah and cultivated areas occupying 25.87% and 25.40% by 2015. The results showed that during the periods 1984-1990, 1990-2000, 2000-2011 and 2011-2015, the park experienced alternating positive and negative evolutions whose trend indices are Ti [(38, 6); 2D]; Ti [(65, 22); 3D]; Ti [(78, -82); 4a] and Ti [(58, -36); 3c]; the second and the third periods being the most devastating and beneficial ones for conservation. Finally, between 1984 and 2015, the park undergone a negative evolution of trend index Ti [(77, -64), 4b] characterized by “a very strong evolution (4) with “a strong negative trend (b) which is represented by spatial transformations affecting 77% of the park, consisting of 82% degradation and 18% increase, resulting in a negative result of 64%. During that time, the park lost 29.9% of the vegetation cover and 31.2% of water resources in favor of anthropized areas, which increased by 94.5%. The decline of the vegetation cover is dominated by savannah and forest loss dynamics. Land cover changes are mainly caused by anthropogenic pressures and the variability of climatic conditions. They are due to six spatial processes which are dominated by patch creation and patch attrition. The results also revealed a high degree of coherence between spatial processes, class dominance and trend indicators. In general, class dominance decreases are linked to patch degradation processes and vice versa. Patch degradation processes such as fragmentation lead to negative evolutions if they affect vegetation and positive developments when they affect anthropized zones and vice versa, for patch development processes like enlargement.

Características Ecosistémicas asociadas a la actividad ganadera en Arauca (Colombia): Desafíos frente al cambio climático

En la llanura inundable de la Orinoquía colombiana (departamento de Arauca) se realizó la caracterización de cuatro tipos ecosistémicos con diferentes grados de intervención por ganadería, durante la intensa temporada seca de enero a marzo 2010: sabana de pastizal, sabana arbolada, bosque de galería y bosque conservado del piedemonte. En cada uno de ellos se evaluaron las condiciones microclimáticas (humedad y temperatura del aire), las características físico químicos del suelo (capacidad de retención de agua, capacidad de intercambio catiónico, pH, contenido de fósforo y de micronutrientes), la diversidad vegetal (riqueza y abundancia) y el potencial regenerativo (diversidad y porcentaje de germinación del banco de semillas del suelo), con el fin de establecer cuáles parámetros ecosistémicos son los más afectados por la ganadería durante la sequía, y evaluar la capacidad de regulación ambiental y el potencial de recuperación natural. Los resultados demostraron que en casi todos los aspectos el tipo ecosistémico de pastizal es ampliamente contrastante con relación a los bosques conservados del piedemonte, siendo estos últimos los lugares con mayor biodiversidad, menor variabilidad en temperatura y humedad relativa, mayor capacidad de retención de agua, mayor variabilidad topográfica que brinda sitios específicos de regeneración y contenidos más balanceados de micronutrientes en el suelo. Los bancos de semillas, que albergan propágulos que soportan la temporada seca para germinar en condiciones más favorables, fueron más diversos y abundantes en la sabana arbolada, mostrando que este ecosistema tiene mayores opciones de recuperación ecológica que la sabana de pastizal. El estudio demuestra la importancia de la cobertura arbórea en la llanura inundable, especialmente en la autorregulación ecosistémica durante temporadas climáticas desfavorables. Se recomienda la implementación de sistemas de producción ganadera que involucren el componente forestal, y la conservación de los remanentes de bosque.Palabras clave: Bosque de galería; bosque del piedemonte Orinoquía; pastizal; regulación climática; sabana arbolada; suelo; Gallery forest; piedmont forest; Orinoquía; pastureland; climate regulation; wooded savannah; soil.

Microvertebrates from unit G/layer 17 of the archaeological site of Hummal (El Kowm, Central Syria): Preliminary results

We present a first look at the microvertebrate fauna of the Middle Pleistocene site of Hummal in Central Syria. Some 2000 microvertebrate remains (1200 mammalian; 230 reptilian; 600 unidentified) were found in unit G/layer 17 by screen-washing sediments in an area of 4m2. The following taxa have been identified: Reptilia: Agaminae indet., Gekkota indet., Lacertidae indet. (2–3 taxa), Eryx sp., Natricinae indet.; and Mammalia: Crocidurinae indet., Chiroptera indet., Lepus sp., Arvicolinae indet., Ellobius sp., Microtus sp., Murinae indet. (large form), Mus sp., Meriones sp., Gerbillus sp. The presence of Ellobius indicates a Middle Pleistocene age of the fauna. This genus does not occur in Syria today, but is recorded in Israel in Late Acheulean to Early Mousterian sites. In North Africa, the occurrence of this genus is restricted to the early part of the Middle Pleistocene. The ecological requirements of the nearest living relatives of the recorded taxa indicate mainly open habitats, but also the presence of vegetation and wet conditions, at least close to the site. Lepus, Ellobius, Meriones, Gerbillus, and Eryx live to various extents in steppes, semi-deserts, and deserts. Various extant species of large murids that come into consideration occupy a variety of wooded habitats, grassland and savannah and require the presence of water. Hummal offers the most detailed Pleistocene portrait yet of hominin palaeoenvironment in an area that, at the end of the Pleistocene, became known as part of the Fertile Crescent.

The European ruminants during the "Microbunodon Event" (MP28, Latest Oligocene): impact of climate changes and faunal event on the ruminant evolution.

The Earth already experienced numerous episodes of global warming and cooling. One of the latest impressive events of temperature rising was the Late Oligocene Warming that occurred around 25 Mya. An increase of the marine temperature of 2 to 4°C has been observed in a short time interval. In Europe, this major climatic event can be correlated to the continental faunal turnover “Microbunodon Event”. This event is marked by a huge faunal turnover (40% of the ungulate fauna during the first 500k years) and environmental changes. Drier conditions associated to the appearance of the seasonality lead to new environmental conditions dominated by wooded savannahs. This is correlated to a major arrival of Asiatic immigrants. Moreover, from a homogenous fauna during the main part of the Oligocene, local climatic variations between the European Western coast and the more central Europe could have provided faunal regionalism during the latest Oligocene and earliest Miocene. Considering the ruminants, this event is the major ever known for this group in Europe. A total renewal at the family level occurred. Thanks to a precise stratigraphic succession, major evolutionary elements are highlighted. Typical Oligocene species, mainly Tragulina, were adapted to wooded environments and were leaves/fruits eaters. They disappeared at the end of MP27 or the early MP28. This corresponds to the appearance of the Asiatic immigrants. The Tragulina (Lophiomerycidae, Bachitheriidae) and stem Pecora gave way to more derived stem and maybe crown Pecora (e.g. “Amphitragulus”, Babameryx, Dremotherium). These newcomers were adapted to more open environments and mixed feeding. The disappearance of the Tragulina is probably linked to environmental and vegetation changes, and competition. They give way to more derived ruminants having a more efficient metabolism in drier conditions and a better assimilation of less energetic food.

Sensitivity of East African savannah vegetation to historical moisture-balance variation

Abstract. Fossil pollen records provide key insight into the sensitivity of terrestrial ecosystems to climate change. However, tracing vegetation response to relatively modest historical climate fluctuations is often complicated by the overriding signature of anthropogenic landscape disturbance. Here we use high-resolution pollen data from a ~200-year lake-sediment record in open wooded savannah of Queen Elizabeth National Park (southwestern Uganda) to assess the sensitivity of the tropical lowland grassland–forest transition to historical, decade-scale moisture-balance fluctuations. Specifically we trace vegetation response to three episodes of higher average rainfall dated to the 1820s–1830s, ca. 1865–1890 and from 1962 to around 2000. Our pollen data indeed reveal a sequence of three wet periods, separated by two drier periods. During the inferred wetter episodes we find increases in the percent pollen abundance of trees and shrubs from moist semi-deciduous forest (Allophylus, Macaranga, Alchornea, Celtis), riparian forest (Phoenix reclinata) and wooded savannah (Acalypha, Rhus-type vulgaris, Combretaceae/Melastomataceae) as well as taxa common in the local rift-valley grasslands (Acacia, Ficus), together creating strong temporary reductions in Poaceae pollen (to 45–55% of the terrestrial pollen sum). During intervening dry periods, Poaceae pollen attained values of 65–75%, and dryland herbs such as Commelina, Justicia-type odora and Chenopodiaceae expanded at the expense of Asteraceae, Solanum-type, Swertia usambarensis-type, and (modestly so) Urticaceae. Noting that the overall richness of arboreal taxa remained high but their combined abundance low, we conclude that the landscape surrounding Lake Chibwera has been an open wooded savannah throughout the past 200 years, with historical moisture-balance variation exerting modest effects on local tree cover (mostly the abundance of Acacia and Ficus) and the occurrence of damp soil areas promoting Phoenix reclinata. The strong apparent expansion of true forest trees during wet episodes can be explained partly by enhanced pollen input via a temporarily activated upland stream. Pollen from exotic trees and cultural indicators appears from the 1970s onwards, but their combined influence fails to mask the signature of natural vegetation dynamics in the pollen record.

A gender analysis of perceived climate change trends and ecosystems-based adaptation in the Nigerian wooded savannah

abstractThe Article investigates perceived climate change trends and the types of ecosystem-based adaptation that were adopted by various gender groups in the Nigerian wooded savannah.The study sourced data via a household survey, key-informant interviews and three focus group discussions in 11 communities in the study area. The study shows that the livelihoods of both male and female groups in the study population are ecosystem based. Perceived changes in the local climate included delay in the onset of rain, reduction in the total annual rainfall and early cessation of the rainy season which affected the livelihoods of men and women differently. Common ecosystem-based adaptation options are based on the impacts and the need for livelihood support, charcoal production by men, while women engaged in gardening and seed harvesting. The study also showed that uncontrolled harvesting of forestry resources without replanting have negative implications for terrestrial ecosystems and the livelihoods of both the male and female population groups in the study area. The study found that sustainable ecosystems will be enriched by involving a full range of capacity development that is beneficial to both gender groups at local and national level.

Protected areas in Cameroon from Rio to Rio+20 (1992–2012)

SUMMARY The Convention on Biological Diversity (CBD) recognizes protected areas (PAs) as instrumental in fostering the attainment of international targets. At the end of the Rio+20 in Brazil, this paper focuses on PAs created in Cameroon since 1992. Statistics from the World Database on Protected Areas (WDPA), and other sources illustrate that 15 PAs covering 1 901 739 hectares have been created and 13 others enclosing 666 026 hectares are at different stages of creation. They are 11 national parks covering 1 806 928 hectares representing 95% and 4 sanctuaries wrapping up 5% (94 811 hectares). The tropical humid ecosystem has 56% of the area protected; the tropical wooded savannah 30% and the montane ecosystem 7%. PAs overlap significantly (96%) with Key Biodiversity Areas suggesting they are conferring some protection on biodiversity.

Assortative mating in mixed swarms of the mosquito Anopheles gambiae s.s. M and S molecular forms, in Burkina Faso, West Africa

The molecular form composition of Anopheles gambiae Giles s.s. (Diptera: Culicidae) mating swarms and the associated mating pairs (copulae) were investigated during two rainy seasons (July to October, 2005 and July to November, 2006) in the villages of Soumousso and Vallée du Kou (VK7). Although the habitats of these villages differ markedly, sympatric populations of M and S molecular forms of An. gambiae s.s. occur in both places periodically. The main aim was to assess the degree to which these molecular forms mate assortatively. In Soumousso, a wooded savannah habitat, the majority of swarm samples consisted of only S-form males (21/28), although a few M-form males were found in mixed M- and S-form swarms. In VK7, a rice growing area, the majority of swarm samples consisted of only M-form males (38/62), until October and November 2006, when there were nearly as many mixed-form as single-form swarms. Overall, ∼60% of M- and S-form swarms were temporally or spatially segregated; the two forms were effectively prevented from encountering each other. Of the remaining 40% of swarms, however, only about half were single-form and the rest were mixed-form. Of the 33 copulae collected from mixed-form swarms, only four were mixed-form pairs, significantly fewer than expected by random pairing between forms (χ(2) = 10.34, d.f. = 2, P < 0.01). Finally, all specimens of inseminated females were of the same form as the sperm contained within their spermatheca (n = 91), even for the four mixed-form copulae. These findings indicate that assortative mating occurs within mixed-form swarms, mediated most probably by close-range mate recognition cues.

Some implications of terrestrial ecosystems response to climate change for adaptation in Nigeria's wooded savannah

Knowledge of non-linear and variable climate risks generated by the interaction between climate and terrestrial ecosystems at local spatial scales is important for place-based and context specific adaptation. In this study we generated 24 risk factors from 9 climate risk determinants based on the trend in present and future climate, water footprints associated with climate–ecogeographic interactions, climate–land cover relations and socio-demographic profiles. The description of aggregate climate risk was compared across community clusters, local government areas, and 3 broad zones in the wooded savannah of Nigeria. The results suggest rainfall, which is increasing at about 0.6mm/decade under the present climate will decline by about 4mm/decade under future climate. Future maximum temperature is projected to increase by about 0.02°C/decade, a rate that is lower than the present 0.06°C/decade. Rainfall was found to be the most important determinant of ecosystem changes and propagation of natural resource systems and the livelihoods they support. Climate risks vary spatio-temporally across zones, local government areas and community clusters with strong orientation to water (rainfall) footprint. The likelihood of the geographic shifting of risks such as loss of arable lands and human migration from moisture deficit areas to more favorable areas due to the changing water footprint is high.

Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)

Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions, consistent with major seasonal variations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q &lt; 1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~30% higher and bicarbonate fluxes were ~35% lower than previous reports. DIC represented 58% of the total annual C flux, and under the assumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~50% of terrestrial-derived riverine C transport.

Local Climate Forcing and Eco-Climatic Complexes in the Wooded Savannah of Western Nigeria

Many climate impact applications are sensitive to local differentials in the climate system. This study investigates how eco-geographic factors influence the local climate and propagate eco-climatic complexes that vary spatio-temporally. Local geography data including elevation, slope, aspect, rainfall, temperature, vegetation, population density, and soil potential for agriculture were integrated and analyzed using geographic information system and principal component analysis. The result was profiled for local climate drivers and associated spatial structures in present and future climate (2046-2065) scenarios. The results suggest a local climate system driven by the coupling between terrain, rainfall and temperature in all seasons. In the present climate, this coupling creates eco-climatic complexes that extend from the southeast to northwest corridor in all seasons except June-July-August (JJA) when it is shifted to the northeast axis. This pattern is projected to continue in the future climate scenario, but its spatial influence and intensity would weaken around the northwest axis and rainfall will become less significant in the system in JJA. The clustering of rural settlements these complexes suggests the climate-positives produced by the system significantly support rural livelihoods. Thus, these eco-climatic complexes represent climate sensitive natural resource systems that should be targeted as a fulcrum for climate change mitigation and adaptation in the wooded savannah.

Influence of drought on predation of elephant (Loxodonta africana) calves by lions (Panthera leo) in an African wooded savannah

AbstractData were collected on species killed by lions Panthera leo in Hwange National Park, Zimbabwe between 1998 and 2004. Lions killed predominantly large to medium‐sized herbivores, concentrating on buffalo Syncerus caffer, elephant Loxodonta africana, giraffe Giraffa camelopardalis, wildebeest Connochaetes taurinus and zebra Equus burchelli. These species made up 83% of all lion kills found and 94% of the biomass of kills actually observed. Elephant calves made up an unusually large proportion of lion prey during the study period (23% of kills recorded). All elephants killed were dependent juveniles. Elephant calves appear more vulnerable during the dry months of the year, particularly in years of below average rainfall. Elephant calves are usually well protected. However, high‐density aggregations of elephants around limited water sources during the dry season may deplete local food resources, forcing elephant herds to travel large distances between water and forage. Under these circumstances, elephant calves may become lost or separated from family groups, accounting for their high incidence in lion diet.

Palaeoenvironments of Lake Assom near Tibati (south Adamawa, Cameroon). What happened in Tibati around 1700 years BP?

Two vibrodrill and six core drill cores were recovered in Lake Assom near Tibati, south of Adamawa. From eight radiocarbon ages on samples from the two vibrodrill cores and on the basis of sedimentological analysis, a reconstitution of the environmental history of this site for the late Holocene has been done. These results suggest the Lake Assom has remained swampy or even dry since 2800 years BP. Spectacular deposition of compact muddy intraclasts strongly suggests that this situation was suddenly interrupted close to ≈1700 years BP when the lake was inundated by water. This deposition can be compared to that of coarse materials observed at the base of the erosion profile “Basse Terrasse”. In spite of this present filling trend, the lacustrine state of the site seems to still pertain. Observations done on the lake banks and the occidental swampy plain, compiled with those from the well in the centre of the small adjacent depression of Ngwana, enable us to better understand the recent functioning of the lake. The Mandjara river certainly played a major role in the sedimentation of sandy gley, and later in the high energy reworking of older coarse intraclasts at ≈1700 years BP. Lake Assom seems to have originated from the dissolution of a more extensive iron crust covering the hole region of Mbella Assom. The presence today of two adjacent depressions is due to local morphology following changes in the lake during the dry period. On the other hand, palynologic studies show no indication of the proximity of any humid forest to this wooded savannah over the past 4500 years BP.

The carbon isotope record in soils along a forest-cerrado ecosystem transect: implications for vegetation changes in the Rondonia state, southwestern Brazilian Amazon region

This paper presents carbon isotope data on soil organic matter (SOM) collected along an ecosystem transect that includes a wooded savannah (cerrado), a tropical semideciduous forest (cerradão), a forest tran sition type and a tropical forest. The study area is located in the Rondonia state, southwestern Brazilian Amazon region. 14C data of total soil organic matter and charcoal indicate that the organic matter in these soils is at least Holocene in age. The forest and forest transition sites are characterized by δ13C soil depth profiles gener ated typically by C3 plants, indicating no major changes in plant communities have occurred in this region during the time period represented by the isotope data. In contrast, the cerrado and cerradão have experienced significant vegetation changes during the Holocene. The d13C data (-30‰ to -27‰) obtained in the deepest part of the profile at the cerradão site show the expansion of the C3 forest vegetation into this region during early Holocene. A vegetation change consisting of increased C4 plant influence is reflected in the 13C-enriched 13C record shows a clear expansion of C3 vegetation, particularly at the cerradão site. The regression/expansion of the forest and savannah vegetation documented at the cerradão and cerrado sites is probably related to changes from a humid to a drier climate and a return to more humid conditions and is in agreement with palaeoclimatic information reported for Brazil and the Bolivian Altiplano. This study suggests that large areas in the Amazon basin have been affected by vegetation changes during the Holocene and that soil organic matter in the transition areas between savannah and forest ecotones contains a valuable palaeorecord of vegetation changes in the Ama zon region.

Heterochromatin heterogeneity and chromosome heteromorphism in Cerdocyon thous (Mammalia, Canidae)

Few cytogenetic studies have been conducted on South American canids. Cerdocyon thous is a representative of the Canidae, living in the forests, open wooded areas and savannahs of South America. Compared to other canid species, C. thous has a large proportion of metacentric and submetacentric chromosomes as well as a large amount of constitutive heterochromatin, especially along the short arm of submetacentric chromosomes. In the present study, different chromosome banding methods were used to characterize the heterogeneous nature of the large heterochromatic segments and to propose an organizational model for this segment that occupies the entire short arm of most two-armed chromosomes. Furthermore, chromosome heteromorphism related to the short arm of large submetacentric chromosome corresponding to no. 3 in male and female karyotypes is described.

The Origins of Agriculture in West Africa

IN THE sub-tropical zone, it is easy to fix a line between pre-agricultural cultures and cultures which understood agriculture even if they did not widely practise it. The grains of cereal grasses and of food plants like rice and maize are of use as food only if collected in bulk, and they need preparation by grinding and cooking, which can also be practised only in bulk. The yield from each plant is fairly small, so there would be little reward for labour if grain-ears and cobs had to be collected from among many other plants in an untilled countryside. It was therefore necessary to prepare a patch of ground, sow the seeds, keep the field reasonably free of weeds, and reap the crop. It is thought possible that the Middle East went through a protoagricultural stage in which wild grasses were reaped. This would be feasible in dry savannah, where little save grasses would grow, and they would reach maturity at about the same time; but the food yield must have been meagre. In contrast, the wooded savannah and equatorial forest produce some useful seeds and fruits, but the bulk carbohydrate which forms the basis of modern diet can be obtained only from tubers, especially yams and Coleus. Since tubers are even less likely than cereal grains to leave

Ecology and host-relationships of ticks (Ixodoidea) infesting domestic animals in Kassala Province, Sudan, with special reference to Amblyomma lepidum Dönitz.

Amblyomma lepidum Dön., previously incriminated as a vector of heartwater (caused by Rickettsia ruminantium) among sheep and goats, and possibly camels, in southern Kassala Province, Sudan, is apparently the only Amblyomma species in this area. Systematic collections of all ticks infesting domestic animals were carried out in November 1959, just after the rains, in five ecologically differing areas in the region most severely infected with heartwater. Though rare in desert scrub (north of 16°N. latitude) and only moderately numerous in semidesert grassland (Butana area), incidence of A. lepidum is high in wooded savannah (River Atbara) and in the cultivated Gash Delta, and highest (15·5 per host) in the Acacia seyal savannah of the River Gash. Chief hosts of adults are cattle. Sheep are secondary hosts, and camels, donkeys, and goats are less heavily infested. Two males were taken feeding on humans. Mating (breeding) activity is only slight following the rains (November). Few larvae and nymphs were found during this period; those present were mainly on sheep and goats, with a few on cattle, and these were usually feeding on the hoofs of their hosts.Rhipicephalus s. sanguineus (Latr.), the most numerous and widely distributed tick here, infests chiefly sheep and goats, is common on cattle, and also occurs on camels and donkeys. Mating activity of this species is high in November. Hyalomma dromedarii Koch is equally widely distributed and follows R. s. sanguineus in numbers, but is most frequent on camels, common on cattle, and rare on donkeys and sheep; goats were uninfested. Mating is moderately active at this season. The incidence of H. impeltatum Schulze &amp; Schlottke, which occurs in each zone, equalled that of A. lepidum. Cattle are the chief hosts and camels are secondary hosts; donkeys, sheep, and goats are less frequently infested. Mating activity is moderate in November.Other more or less common tick species on these domestic animals are Boophilus decoloratus (Koch), R. e. evertsi Neum., R. simus Koch, H. anatolicum excavatum Koch, H. truncatum Koch and H. marginatum rufipes Koch, evidence for the status of which as a subspecies of H. marginatum Koch is to be presented in a subsequent paper. Several other rare species are also recorded.