Early Dry Season Research Articles

Influence of early dry season fires on primary production in western Serengeti grasslands, Tanzania

Short-term, i.e. 4-9 weeks aboveground net primary production (ANPP) temporal patterns during the first post-fire year in western Seren-geti National Park, and potential differences in the factors limiting ANPP between burnt and non burnt grasslands were examined and es-tablished. Fire stimulated growth at early post-fire stages, even during the dry season, July-October and led to larger increments in green phytomass compared to the non burnt grassland at the onset of short rains, Octo-ber-December. Further, ANPP in burnt plots correlated well with the ratio leaf/total standing phytomass suggesting that the accumulation of standing dead material can be a limiting factor to ANPP in burnt grass-lands. However, ANPP in burnt plots was unrelated to rainfall contrary to earlier arguments, but reached peak earlier and declined early in the rain season, perhaps due to the interactive effects of fire and grazing in the area. In non burnt plots, the temporal change in ANPP was more related to rainfall availability, at least until mid-growing season. Also, the phytomass structure differed between burnt and non burnt grasslands, and together with litter did not recover to non burnt levels within the first post-fire year. The study has demonstrated that the desire of the fire man-agement program in Serengeti National Park, which is to supply green forage to both migra-tory and resident populations during dry season is being fulfilled.

Long‐distance Dispersal of Invasive Grasses by Logging Vehicles in a Tropical Dry Forest

ABSTRACTPredicting responses of vegetation to environmental factors in human‐altered tropical ecosystems requires an understanding of the controls on plant population expansion across landscapes (i.e., long‐distance dispersal) as well as of factors affecting recruitment at local scales (i.e., microsite conditions). We studied the roles of light availability, habitat type, soil disturbance, and seed dispersal in a selectively logged forest in lowland Bolivia where the exotic forage grass Urochloa (Panicum) maxima is abundant on roads and log landings but does not invade felling gaps or unlogged forest. Shade‐house trials and seed addition experiments with U. maxima revealed that this C4 grass thrives in high light but also grows in partial shade (10% full sun, but not 1% full sun), and that felling gaps, but not undisturbed forest, are suitable for grass establishment. To determine if seed dispersal by logging vehicles explains the discrepancy between actual and potential grass recruitment sites, we collected grass seeds that fell from trucks onto log landings located long distances (>500 m) from established grass populations. Trucks dispersed an estimated 1800 alien grass seeds per log landing during the early dry season; automobiles also transported seeds of grass (135 seeds/vehicle). The seeds collected (and relative abundances) were the exotics U. (Panicum) maxima (97%) and Urochloa (Brachiaria) brizantha (2%), and the pan‐tropical weeds Sorghum halapense (1%) and Rottboellia cochinchinensis (0.2%). Grasses invade this forest where disturbance coincides with seed dispersal by motor vehicles, while dispersal limitation apparently prevents invasion of many sites otherwise suitable for grass recruitment (i.e., felling and natural gaps).

Fine-scale Patchiness of Burns in a Mesic Eucalypt Savanna Differs with Fire Season and Sorghum Abundance

Canopy tree populations in the eucalypt savannas of northern Australia consistently show bottlenecks in the transition of young trees to the canopy layer. This is most likely due to frequent fires, where young trees are caught in a 'fire trap', suffer topkill and regenerate from underground tissues year after year. Little is known of fire behaviour at the spatial scale of individual juvenile trees. This paper presents field measurements of small-scale, 10 cm (microsite), burn patterns and patch sizes following set fires in the early dry season, late dry season, and wet season. Fire treatments were repeated in plots dominated by a native annual grass (Sorghum) and in others with little or none of this grass. Both late dry season and wet season fires left few or no microsites unburnt, regardless of understorey type. With early dry season fire, however, understorey type made a difference: 47% of the microsites were left unburnt in plots with little or no Sorghum compared to only 5% in Sorghum-dominated plots. Further, the early dry season fire pattern was very patchy, resulting in both large and small areas of burnt vegetation. In Sorghum-dominated plots, more than half the patches were greater or equal 10 m in size and only a third were < 3 m in size, whereas in plots with little or no Sorghum, 99% of burnt patches were < 10 m in size, and 41% were < 0.5 m in size. Thus, only a regime of early dry season fire with little or no Sorghum in the understorey creates potential 'windows of escape' for juvenile trees. The study has implications for management of savanna trees by fire.

Bayesian network models for environmental flow decision making in the Daly River, Northern Territory, Australia

ABSTRACTThis paper reports the development and application of two Bayesian Network models to assist decision making on the environmental flows required to maintain the ecological health of the Daly River (Northern Territory, Australia). Currently, the Daly River is unregulated, with only a small volume of water extracted annually for agriculture. However, there is considerable pressure for further agricultural development in the catchment, particularly with demand for extra water extraction during the dry season (May–November).The abundances of two fish species—barramundi (Lates calcarifer) and sooty grunter (Hephaestus fuliginosus)—were chosen as the ecological endpoints for the models, which linked dry season flows to key aspects of the biology of each species. Where available, data were used to define flow–fish habitat relationships, but most of the relationships were defined by expert opinion because of a lack of quantified ecological knowledge.Recent field data on fish abundances were used to validate the models and gave prediction errors of 20–30%. The barramundi model indicated that the adult sub‐population was key to overall fish abundance, with this sub‐population particularly impacted by the timing of abstraction (early vs. late dry season). The sooty grunter model indicated that the juvenile sub‐population dominated the overall abundance and that this was primarily due to the amount of hydraulically suitable riffle habitat. If current extraction entitlements were fully utilized, the models showed there would be significant impacts on the populations of these two fish species, with the probability of unacceptable abundances increasing to 43% from 25% for sooty grunter and from 36% for barramundi under natural conditions. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Soil pore characteristics of evergreen and deciduous forests of the tropical monsoon region in Cambodia

AbstractBoth evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low Ks at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWCsm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m3 m−3, respectively. The mean coarse pore volume of the soil matrix (CPVsm) in the Ef and Df groups was 0·231 and 0·115 m3 m−3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effect of fires on soil nutrient availability in an open savanna in Central Brazil

Fire is common in savannas but its effects on soil are poorly understood. We analyzed long-term effects of fire on surface soil of an open Brazilian savanna (campo sujo) in plots submitted to different fire regimes during 18 years. The five fire regimes were: unburned, quadrennial fires in middle dry season, and biennial fires in early, middle or late dry season. Soil was collected during the wet and the middle dry season of 2008, and analyzed for pH, organic matter, total N, potential acidity, exchangeable cations and available P, S, Mn, Cu, Zn and Fe. We applied multivariate analysis to search for patterns related to fire regimes, and to local climate, fuel, and fire behavior. Spearman test was used to establish correlations between soil variables and the multivariate analysis gradient structure. Seasonal differences were tested using t-test. We found evidence of long-term fire effects: the unburned plot was segregated mainly by lower soil pH; the quadrennial plot was also segregated by lower soil pH and higher amount of exchangeable cations; the time of burning during the dry season in biennial plots did not significantly affect soil availability of nutrients. Differences in elements amounts due to the season of soil sampling (wet or dry) were higher than due to the effect of fires. Higher availability of nutrients in the soil during the wet season was probably related to higher nutrient inputs via rainfall and higher microbial activity.

Animal diet botanical composition compared with pasture species composition as indicators for pasture status in the semi-arid rangeland of Sudan (South Darfur State)

ABSTRACT A study was conducted during the period 2006/08 in the semi-arid rangeland of South Darfur State, Sudan at Eldien locality (latitudes 9°-30 and 11°-45 north and longitudes 25°-30 and 27° east, ecologically in the low rainfall woodland savannah with an annual rainfall between 400-600 mm).. The objective of the study was to evaluate animal diet botanical composition in comparison with pasture species composition as indicators for pasture status in the area. Data were collected for pasture species composition (Parker loop method, 1955) and animal diet botanical composition (Van Dyne Method,1968) over two years both in early wet and late dry summer seasons. Results showed that diet botanical composition was composed of pure herbaceous plant species during rainy and early dry summer seasons and a mixture of browse and herbaceous species in the late dry summer season. Calcium in animal diet was present in a suitable concentration, whereas phosphorous was present at low concentration. Although the percent species composition of the natural pasture provides an indicator of range composition, animal diet botanical composition could be used as an indicator of the pasture status. Both parameters could be very useful in designing range management practices, such as selecting species required for reseeding deteriorated range and in identifying key species that will form a base for range management.

Aspects of the seed ecology of Acacia karroo in the Eastern Cape, South Africa

Seed ecology may play a role in the widespread increase of Acacia karroo in savanna and grassland. Accordingly, fecundity, predation, mortality by fire, dispersal by livestock, and seed longevity were studied. Seed production per tree (P of pod production, pods per tree) was positively related to tree height, negatively related to tree density, and was greater for sites receiving run-on. Predispersal predation by bruchids, cerambycids, and wasps depleted seed production by 18%. The ant Messor capensis effectively eliminated surface seed except during the early dry season following seed shed. Rodent predation of seed was minimal. Fires >100 °C killed most exposed seed but a thin layer of soil increased survival and maintained germinability. A greater proportion of ingested seeds passed through cattle (57%) and sheep (50%) than through goats (15%). 50% of seeds were recovered within 48 h. During passage, soft seeds were digested, some hard seeds were softened, but most were egested as hard seeds; germinability was not increased. Cattle were confirmed as dispersal agents. Using experimental seed banks, it was shown that buried or surface-exposed seeds did not persist for longer than a year, but 24% of surface-shaded seeds persisted for two years. Most seeds germinated but most buried seeds died before emergence. Seed persistence in deep shade should facilitate invasion into grassland. Seed banks of. A. karroo did not exceed 18 seeds m−2 because of the above-described effects. Seed availability (fecundity, dispersal by cattle, seed longevity) is concluded to contribute to the invasiveness of A. karroo, but use of fire may offer partial control of seed availability.

Spatial clustering and associations of two savannah tsetse species, Glossina morsitans submorsitans and Glossina pallidipes (Diptera: Glossinidae), for guiding interventions in an adaptive cattle health management framework

The paper deals with tsetse (family Glossinidae) control and aims at improving the methodology for precision targeting interventions in an adaptive pest management system. The spatio-temporal distribution of Glossina morsitans submorsitans Newstead, and Glossina pallidipes Austen, at Ethiopia's Keto pilot site, is analyzed with the spatial analysis by distance indices (SADIE) methodology that focus on clustering and spatial associations between species and between sexes. Both species displayed an aggregated distribution characterised by two main patches in the south and an extended gap in the north. Spatial patterns were positively correlated and stable in most cases, with the exception of the early dry season and the short rainy season when there were differences between the species and sexes. For precision targeting interventions, the presented methods here are more effective than the previously used geostatistical analyses for identifying and delimiting hot spots on maps, measuring shapes and sizes of patches, and discarding areas with low tsetse density. Because of the improved knowledge on hot spot occurrences, the methods allow a better delimitation of the territory for control operations and a more precise computation of the number of the relatively expensive traps used for monitoring and control purposes.

Assessing multi-temporal Landsat 7 ETM+ images for estimating above-ground biomass in subtropical dry forests of Argentina

Above-ground biomass (AGB) is important to estimate total carbon pools in forests, where it has a key role in the global carbon cycle. We assessed correlations between spectral information and ground data to estimate AGB in the Semiarid Chaco, Argentina. Ground data (DBH, height and species of trees) were obtained from 15 samples (0.8 ha each) and AGB was estimated. Multi-temporal Landsat images were used to obtain spectral data (single bands/vegetation indexes) of the samples. Correlation tests between AGB and spectral bands and between AGB and vegetation indexes were performed for all dates. A strong correlation was found between spectral indexes and AGB in the early dry season (fall – May 12, 2002) while poorer results were obtained for summer and winter. This would result from a differential phenological response of trees, shrubs and grasses to environmental conditions. A biomass predictive model was fitted using the NDVI of May 12, 2002 and a biomass map was obtained applying this regression. There was a rain-related regional pattern of AGB decrease in an east–west direction, and a land-use related local pattern. Our results offer a great potential for increasing the understanding of dry Chaco forest structure and for improving carbon pools estimates.

Exploiting the heterogeneous drop-off rhythm of Amblyomma variegatum nymphs to reduce pasture infestation by adult ticks

Tick distribution depends on the drop-off rhythm of the previous stage and on the suitability for tick survival of the environment where they are disseminated. Studies were implemented in Burkina Faso to assess detachment pattern of engorged Amblyomma variegatum nymphs. Experiments were carried out with naturally infested cattle kept in a paddock or monitored when grazing community pasture. In the pasture, 80% of the nymphs detached between 14.00 h and 17.00 h while less than 25% did so in the paddock. Further investigation was implemented to assess whether the density of adult ticks might be modified by herd management. During the early dry season, zebus grazed in 4 plots fenced in natural savannahs and fallows. Two of the plots were used in the morning and the two others in the afternoon. Six months later, zebus were put in these plots, in turn, on 9 occasions. The number of A. variegatum adults picked up by the cattle in each plot was highly variable: they captured more ticks in the plots installed on good lush savannah and 3-fold more ticks in those where the herd had grazed in the afternoon during the previous dry season. An integrated tick control strategy taking these results into account is proposed.

Diet quality estimated with faecal near infrared reflectance spectroscopy and responses to N supplementation by cattle grazing buffel grass pastures

In the seasonally dry tropics the productivity of grazing cattle is often constrained by nutrition, particularly during the dry season. An experiment during 2 annual cycles estimated the diet selected by grazing Bos indicus heifers, and their growth and growth responses to a non-protein N supplement. Two drafts (groups) of 2 herds (10 heifers per herd) grazed a pasture consisting of buffel grass ( Cenchrus ciliaris) with some legume and edible browse, and herds were offered loose mineral mix (LMM) supplements either without (control) or with urea. Near infrared reflectance spectroscopy measurement of faeces (F.NIRS) was used to estimate each 2 weeks the non-grass and crude protein (CP) concentrations, and DM digestibility (DMD) of the diet selected. Rainfall and diet quality generally followed the seasonal pattern expected for the region and for the seasonally dry tropics. Non-grass ( i.e. dicotyledonous species) content averaged 0.13 (S.D. 0.053) of the diet and did not appear to be related to season, but during the first dry season and wet season the urea supplemented heifers selected diets lower ( P<0.01 and P<0.05, respectively) in non-grass than the control heifers. Diet quality was generally low during the dry seasons, increased sharply after the seasonal break, and later declined gradually through the wet seasons and wet-dry transition seasons. During the dry seasons average diet CP ranged from 33 to 49 g/kg and diet DMD from 0.480 to 0.507. During the 2 wet seasons CP averaged 94 and 100 g/kg, and the DMD 0.591 and 0.601. The control treatment heifers lost 30 and 32 kg LW during the late dry seasons, and gained 143 and 136 kg during the wet, wet-dry transition and early dry seasons of Drafts 1 and 2, respectively. F.NIRS predicted the daily weight gain (DWG) of the heifers with accuracy useful for management purposes except during the early wet season of Draft 2 when intermittent rains increased diet quality but were insufficient for substantial pasture growth. The urea supplement reduced ( P<0.01) heifer LW loss during the dry seasons, but much of this benefit subsequently disappeared due to compensatory growth; net benefit of the urea supplement over the annual cycle was 24 and 14 kg in the 2 drafts. This study demonstrated the capacity of F.NIRS to estimate the diet selected, liveweight change and liveweight responses to a N supplement in grazing cattle.

Role of perithecia as an inoculum source for stem rot type of pepper root rot caused by Fusarium solani f. sp. piperis (teleomorph: Nectria haematococca f. sp. piperis)

Pepper (Piper nigrum L.) root rot caused by Fusarium solani f. sp. piperis (FSP; teleomorph: Nectria haematococca f. sp. piperis) includes two symptom types called root rot (RR) type and stem rot (SR) type. In this study, the temporal and spatial associations between perithecial formation of FSP and development of SR were investigated in naturally infested fields to verify the hypothesis that ascospores from the perithecia are the major inoculum source of the SR type on vines in the field. In surveys of all vines in two neighboring pepper fields every month from December 2005 to November 2006, I mapped the locations of all vines with perithecia and all vines the SR type. The frequency of vines with perithecia increased during April and May, the late rainy season. In June, the early dry season, the number of vines with SR type greatly increased. The vertical range of perithecial formation on the vines extended to 200 cm in height, but was restricted to 30 cm in the dry season in both fields. The join-count statistics showed a significant spatial association between vines with perithecia and vines with SR type in one field (P = 0.042), while no significant spatial association was recognized in another field. The results suggested that ascospores from perithecia of FSP on pepper vines are likely to be one of the main inoculum sources of the SR type of the disease on adjacent vines, but they may not be the exclusive source.

Soil seed banks confer resilience to savanna grass-layer plants during seasonal disturbance

An understanding of soil seed bank processes is crucial for understanding vegetation dynamics, particularly in ecosystems experiencing frequent disturbance. This paper examines seed bank dynamics in a tropical savanna in northern Australia, an environment characterised by frequent fire and highly seasonal rainfall. In particular, we examine the contribution of seed bank processes to the high level of resilience shown by grass-layer vegetation in relation to fire. We assess the spatial congruence between seed bank composition and extant vegetation, document temporal variation in the germinable seed bank over the annual dry season, test the effects of laboratory-applied heat and smoke treatments on seed germinability, and determine the effect of experimental fires on seed bank composition. Although dominant species were shared, the composition of the germinable seed bank was significantly different to that of extant vegetation, with approximately half the extant species not being detected in the seed bank. The density and species richness of germinable seeds was significantly greater in the late dry season than the early dry season, with annual grasses showing particularly high levels of seed dormancy in the early dry season. The density and species richness of germinable seeds in the seed bank was significantly enhanced by laboratory-applied treatments of smoke and especially heat, driven by the response of legumes. However, fire had no significant effect on the density or species richness of germinable seeds in the field, indicating soil temperatures during fire were too low to overcome physical dormancy, or burial was too deep to experience adequate heating or smoke exposure. Our results provide a mechanistic understanding of the persistence of annual grasses and forbs in an environment subject to frequent fire and highly seasonal rainfall, and, together with the sprouting capacity of perennial grasses, explain the high resilience of savanna grass-layer plants in relation to fire.

Breed and Seasonal Variations in the Testicular Morphometry, Gonadal and Extragonadal Sperm Reserves of the Barred Plymouth Rock and Nigerian Indigenous Breeds of the Domestic Fowl

Breed and seasonal influence on testicular morphometry, Gonadal Sperm Reserves (GSR), Extragonadal Sperm Reserves (ESR) was investigated in the barred Plymouth rock and the Nigerian indigenous breeds of the domestic fowl. Twenty sexually matured birds per breed were studied in the four seasons of the year. Breed significantly (p<0.01) influenced the body weight (2.11 +/- 0.05 vs. 1.58 +/- 0.02), paired testes weight (21.92 +/- 1.46 vs. 12.43 +/- 0.91) and all other morphometric parameters with the barred Plymouth Rock showing superiority over the Nigerian indigenous breed. The GSR, ESR and their efficiencies (GSR/g, ESR/g) were highly and significantly (p<0.01) higher in the barred Plymouth rock. Season neither significantly (P>0.05) influenced the testicular morphometric parameters, GSR, ESR nor gonadal sperm reserve/gram testis (GSR/g). The higher numerical differences observed in morphometric parameters, GSR and ESR during the early and late dry seasons suggested that the dry season favors sperm production, hence sperm reserve potentials. The testicular weight was significantly (p<0.001) correlated not only to the body weight (r = 0.63) but to paired Tunica albuginea (= 0.98, p<0.001) and paired epididymal weight (r = 0.69, p<0.001). There was also a significant (p<0.001) and positive correlation between the testicular weight and GSR (r = 0.84, p<0.001). The GSR/g (r = 0.77; p<0.001) ESR (r = 0.86; p<0.001) and ESR/g (r = 0.50, p<0.001). Based on these observations it is concluded that genetic improvement of the Nigerian indigenous breed of the domestic fowl can be carried out by increasing their body weight, hence, testicular weight through crossbreeding with the heavier barred Plymouth rock to achieve improved sperm production and reserve for year round artificial insemination.

Resprouting and mortality of juvenile eucalypts in an Australian savanna: impacts of fire season and annual sorghum

In northern Australian savannas, canopy tree species often have juvenile tree banks that are composed mainly of small individuals of indeterminate age that have resprouted repeatedly after fire. Little is known about their demography. We report the initial responses (mortality, topkill and resprouting type) of 3133 marked juvenile eucalypts to set fires of different seasons (early dry season, late dry season, wet season, unburnt) in a 32 400 m2 field experiment. Fire treatments were repeated in plots dominated by a native annual grass (sorghum) that becomes senescent before the early dry season and provides the main fuel of savanna fires, and in others with little or no sorghum, but instead other native grasses and forbs that remain green well into the dry season. Most juvenile eucalypts &lt;150 cm high were topkilled but resprouted from underground tissues regardless of fire season or understorey (86–100% vs &lt;5% in unburnt plots). Few saplings 200–500 cm high died or were topkilled, but impacts of fire were harsher in sorghum than in non-sorghum vegetation. The response of eucalypts 150–199 cm high was intermediate, suggesting a ‘tactical’ transition from suppressed persistence to growth toward maturity. Counter-intuitively, genet death of juvenile trees was &gt;22% in the low-intensity early dry season fire in plots with little or no annual sorghum, compared with &lt;2% in all other fire/understorey combinations. We suggest results are related to fire behaviour, seasonal carbohydrate storage dynamics and competition with ground-layer plants.

Dry season habitat use by critically endangered white‐shouldered ibis in northern Cambodia

AbstractWe present the first scientific study of white‐shouldered ibis Pseudibis davisoni habitat preferences in dry dipterocarp forest. Foraging sites included seasonal pools, forest understorey grasslands and fallow rice fields, with terrestrial sites used more following rainfall. Habitat and anthropogenic effects in logistic models of foraging site selection were examined by multimodel inference and model averaging. White‐shouldered ibis preferred pools with greater cover of short vegetation (&lt;25 cm) and less of the boundary enclosed, and forest sites with greater cover of bare substrate and lower people encounter rate. At forest sites, livestock density was positively related to bare substrate extent and thus may improve suitability for foraging ibis. At pools, livestock removed tall vegetation between the early and late dry season indicating their importance in opening up foraging habitats after wet season growth. However, by the late dry season, pools with greater livestock density had less short vegetation, the habitat favoured by ibis. Conservation strategies for white‐shouldered ibis must consider a range of habitats, not just seasonal wetlands, and should incorporate extensive grazing and associated burning practises of local communities. Further understanding of the effects of these practices on vegetation, prey abundance and prey availability are therefore needed for effective conservation of this species. This will also develop our understanding of potentially beneficial anthropogenic influences in tropical environments.

Biomass burning influenced particle characteristics in Northern Territory Australia based on airborne measurements

Airborne measurements of particle number concentrations from biomass burning were conducted in the Northern Territory, Australia, during June and September campaigns in 2003, which is the early and the late dry season in that region. The airborne measurements were performed along horizontal flight tracks, at several heights in order to gain insight into the particle concentration levels and their variation with height within the lower boundary layer (LBL), upper boundary layer (UBL), and also in the free troposphere (FT). The measurements found that the concentration of particles during the early dry season was lower than that for the late dry season. For the June campaign, the concentration of particles in LBL, UBL, and FT were (685 ± 245) particles/cm 3, (365 ± 183) particles/cm 3, and (495 ± 45) particles/cm 3 respectively. For the September campaign, the concentration of particles were found to be (1233 ± 274) particles/cm 3 in the LBL, (651 ± 68) particles/cm 3 in the UBL, and (568 ± 70) particles/cm 3 in the FT. The particle size distribution measurements indicate that during the late dry season there was no change in the particle size distribution below (LBL) and above the boundary layer (UBL). This indicates that there was possibly some penetration of biomass burning particles into the upper boundary layer. In the free troposphere the particle concentration and size measured during both campaigns were approximately the same.

The fruit bats (Chiroptera: Pteropodidae) of the Lesio-Louna Reserve, Bateke Plateau, Republic of Congo

Abstract We present the results of the first survey of the fruit bats of the Lesio-Louna Reserve in the Republic of Congo, an area representative of the larger Bateke Plateau region of the country. Mist-netting was conducted in 2002 during four seasonal sampling periods: late wet season, early dry season, late dry season and early wet season. Five species were recorded. Two were frequently trapped, Micropteropus pusillus (n=102 individuals) and Epomops franqueti (n=57). The remaining three were captured only occasionally, Myonycteris torquata (n=5), Hypsignathus monstrosus (n=2) and Megaloglossus woermanni (n=2). In agreement with studies of other fauna, our results confirm that the Bateke Plateau supports species associated with both forest and savanna habitats. However, species typical of forested habitats were also netted in forest edge and neighbouring savanna, suggesting that these species utilise surrounding habitat within the forest-savanna mosaic characteristic of the study area. We found statistically significant seasonal variation in juvenile body mass and forearm length in E. franqueti and in adult female nipple length in M. pusillus, suggesting breeding seasonality in both these species in the reserve.

Prevalence of trypanosome infections in ruminants in the Southern Guinea Savanna, Nigeria.

A survey was conducted to determine the prevalence of trypanosomes in cattle and sheep in Kaura Local Government Area (LGA) of Kaduna State, southern guinea savanna, Nigeria. Animals were sampled in 12 villages from the districts of Bondong, Fada, Kadarko, Kukum, Manchok and Zankan. Sampling visits were undertaken on seasonal basis in the late wet season (October), early dry season (December), late dry season (February) and early wet season (June). Three- ml blood samples were collected from the jugular vein of 395 cattle and 37 sheep. The results revealed that 21.53 ± 1.97% (range 9.4-43.8% per village) of the total animals were infected with various species of trypanosomes, with the prevalence in bovine and ovine being 20.51 ± 2.03% and 32.43 ± 7.69% respectively. Trypanosoma vivax had the highest infection rates (64.52%), followed by T. brucei (18.30%) and T. congolense (17.20%). Infections varied significantly among the districts, ranging from 9.7% at Zankan to 36.9% at Manchok (t=13.08; df=3; p