Late Wet Season Research Articles

Stable isotope signatures of seasonal precipitation on the Pacific coast of central Panama

As calculated from data archived in the IAEA-WMO Global Network of Isotopes in Precipitation programme, the amount-weighted local meteoric water line for the Pacific coast of central Panama is: δ2H = 7.63(±0.08) × δ18O + 6.51(±0.49). Amount-weighted mean isotopic values were regressed against the sea surface temperature (SST) fields of the adjacent tropical oceans. A negative correlation of precipitation isotope composition with Caribbean SSTs is observed only for the early wet season (May–June), whilst the mid-summer dry period is characterized by positive correlation with eastern Pacific SSTs, similar to the late wet season (October–November). The negative response of May–June rainfall isotopic composition to Caribbean SSTs is explained by a SST-mediated change in stratiform rain fraction from organized convective systems proximal to the Inter Tropical Convergence Zone (ITCZ). The positive correlation for the rest of the wet season, when the organized convective zone of ITCZ and its attached stratiform belt are distant from the Pacific coast of Panama, is interpreted as simple evaporative temperature effect on isotopic fractionation.

Weed Specie Composition and Diversity as Influenced by Poultry Manure Rates and Weeding Frequency in Okra

Weed Specie Composition and Diversity as Influenced by Poultry Manure Rates and Weeding Frequency in Okra Adeyemi, O. R; Olaogun, O; Adigun, J. A; Adejuyigbe, C. O Abstract Yield losses in okra are often aggravated by the soil fertility status, weed types and degree of infestation on the field. Field trials were conducted during the early and late wet seasons of 2012 to investigate the influence of poultry manure rates and weeding regime on weed species composition and weed species diversity in okra. The experiment was arranged in a split- plot fitted into a Randomized Complete Block Design with three replicates. The main plot consisted of five poultry manure rates (0, 5, 10 and 15 t ha-1) while the sub plots were five weeding regimes namely: weedy check, weeding at 3 weeks after sowing (WAS); weeding at 3 and 6 WAS; weeding at 3, 5 and 7 WAS and weeding at 3, 6 and 9 WAS. Data were collected on weed specie composition, growth and yield of okra. Data collected were subjected to ecological analysis and analysis of variance as appropriate and significant treatment means were separated using Duncan Multiple Range test at p <0.05. The result shows that thirteen (13) and seventeen (17) weed species were observed in the early and late wet seasons respectively with broadleaves being the most prevalent. In the early wet season weed species diversity (Shannon index H’) (WDI) were mostly reduced in plots weeded 3, 6 and 9 WAP) while the greatest WDI reduction was recorded in plots weeded 3, 5 and 7 WAP. WDI was greater in late wet season than early wet season. Weed dry weights were negatively and significantly correlated with total fruit yield (r = -0.81 and - 0.90) in both early and late wet season respectively. It is therefore concluded that weed types and intensity could be influenced by manure rates and weeding regimes in okra. Full Text: PDF DOI: 10.15640/jaes.v4n1a28

Prevalence of Bovine Trypanosomosis and Its Vector Density in Tembro District, South Eastern Ethiopia

Cross-sectional study was carried out on 554 randomly selected cattle from November 2011 to April 2012 in Tembaro District of Southern Nation Nationalities and Regional State (SNNPR). The objectives were to determine the prevalence and identify different species of trypanosomes affecting cattle in the area known to be infested with tsetse flies with the methods of Buffy coat examination, questionnaire survey and entomological characterization. Based on these methods the prevalence of the study was 52/554 (9.39%) and the disease was statistically significant among body condition scoring (BCS) (x 2 = 7.11; P= 0.03); origins of animals (x 2 =13. 74; P= 0.019) but the opposite scenario were observed between sexes and age groups which means not significant (p> 0.05). However, higher prevalence was revealed in adult animals. The most common trypanosome species identified were Trypanasoma congolense (42/52, 81%) followed by T. vivax (8/52, 15%), mixed (T. congulence+T. vivax) (2/52, 4%). The mean packed cell volume values recorded were 23.38±1 in parasitaemic and 25.3±0.27 in aparasitaemic animals with a statistical significant difference (P<0.05). Based on the questionnaire survey trypanosomosis locally known as ‘Shulula’ and it was identified as primary cattle health problem. Among the respondents 65% of them associated the disease with early dry and late wet seasons. From the asked farmers, 80% know tsetse flies however they do not associate the fly to trypanosomosis transmission. Regarding entomology results a total of 271 flies were collected, 62 were G. pallidipes and 4 stomoxys. In conclusion, trypanosomosis is prevalent in the study area which could affect livestock production and productivity. Therefore, tremendous attention should be given to control both the infection and its vectors.

Screening of onion genotypes against Thrips tabaci Lind. in Central India

Twenty-two (22) genotypes of onion (Allium cepa Lin.) was screened against Thrips tabaci Lind. in the experimental field of Department of Horticulture Maharajpur, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, Madhya Pradesh, India during late wet season in the year 2010-11. The incidence of T. tabaci was observed from 45th standard metrological week (SMW) to 3rd SMW, that is, from transplanting till harvesting, in all the 22 genotypes. The mean T. tabaci population varied from 0.45-6.64 per plant during this period among the genotypes. Out of 22 genotypes of onion screened against T. tabaci, BKHO 1018 had highest yield and was the most tolerant followed by BKHO 1006. Genotype BKHO 1005 was most susceptible and had the lowest yield. T. tabaci appeared in the second week of November, 2010, that is, 12th November (45th SMW) and active up to 3rd week of January. The peak activity of the pest was observed during 1st SMW (last week of December to first week of January). T. tabaci population had significantly positively correlation with the maximum and minimum temperature and sunshine hours; but, it was significantly negative correlated with morning relative humidity. Key words: Genotypes, onion, Thrips tabaci, tolerant.

Fauna edáfica sob diferentes níveis de palhada em cultivo de cana-de-açúcar

Os organismos que constituem a fauna do solo são de grande relevância para os compartimentos serapilheira-solo, por atuarem em importantes processos, como fragmentação do material vegetal, decomposição e ciclagem de nutrientes. Este estudo objetivou avaliar a comunidade da fauna invertebrada do solo sob o cultivo de cana-de-açúcar colhida sem queima, considerando-se a deposição de diferentes quantidades de palhada sobre o solo. Os tratamentos consistiram de diferentes quantidades de palhada de cana-de-açúcar: T0% (0 Mg ha-1); T&lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;25% (2,2 Mg ha-1); T&lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;50% (5,1 Mg ha-1); T &lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;75% (7,8 Mg ha-1); e T&lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;100% (12,0 Mg ha-1). A amostragem aconteceu no período seco e final do período chuvoso, com armadinhas "Pitfall". O número de indivíduos por armadilha ao dia, no período seco, variou entre 11,1 (T0%) e 14,7 (T&lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;25%) e, no período chuvoso, de 15,11 (T0%) a 33,15 (T&lt;img border=0 width=32 height=32 src="../../../../../../img/revistas/pat/v44n4/a02car01.jpg"&gt;75%). Os maiores valores de Shannon foram observados no período chuvoso, e os menores valores de diversidade e equitabilidade resultaram da maior incidência dos grupos Araneae e Formicidae. A quantidade de palhada sobre o solo não proporcionou grande influência nos índices ecológicos e riquezas total e média. A época da coleta influenciou na variação do número de indivíduos, riqueza de espécies, índice de Shannon e de Pielou. Amanutenção da palhada promoveu benefícios para a fauna do solo, em relação ao manejo tradicional.

Spatial and Temporal Distribution of Larval Naked Goby Gobiosoma bosc (Pisces, Gobiidae) in the Middle St. Johns River, Florida

Naked goby (Gobiosoma bosc) larvae were collected from February 2008 through September 2009 at six sites located from 100 to 255 km upstream of the lower St. Johns River estuary. A total of 49,995 G. bosc larvae were collected making it the fourth most abundant species present. Preflexion larvae (3–5 mm standard length (SL)) were collected at all sites and comprised of >55 % of all G. bosc larvae collected. The dominance of preflexion larvae, estimated to be about 2 weeks old, validated that G. bosc were spawning at all sampling sites. Because of the distance involved, and the lack reverse flows due to tidal influence, larval presence was not a result of upstream transport from the estuary. Throughout the study, salinity at all sampling sites averaged between 0.2 and 1.2 practical salinity units (psu), which is below the lower limit of salinity at which this species has been previously reported to spawn. Spawning by G. bosc in the middle St. Johns River in 2008 and 2009 occurred from late March through early August. Spawning in the middle basin appeared truncated compared to the estuary, where reproduction appears to occur well into the fall. Larval G. bosc larvae began appearing in our samples as water temperatures approached 20 °C. Larval density varied significantly both spatially and temporally, but was poorly explained by instantaneous measures of dissolved oxygen, salinity, pH, temperature, Secchi depth, or sampling depth. At sampling sites, where G. Bosc larvae were most abundant, average seasonal densities declined from 74 to 95 % between 2008 and 2009. In August 2008, heavy rains from Tropical Storm Fay caused dramatic flooding over the entire study area and dissolved oxygen concentration at all sampling sites fell to <0.8 mg L−1 from periods ranging from several days to several weeks. We believe this anoxic event caused high larval and juvenile mortality resulting in a nearly complete recruitment failure of the 2008 year class. Since G. bosc rarely survive past age I, recruitment failure of the 2008 year class could explain the between-year decline in larval densities observed. In addition, frequent anoxic events associated with increased streamflow at our most upstream sites during the late summer wet season may also help explain low larval densities at these sites.

Assessing the effect of domain size over the Caribbean region using the PRECIS regional climate model

This study investigates the sensitivity of the one-way nested PRECIS regional climate model (RCM) to domain size for the Caribbean region. Simulated regional rainfall patterns from experiments using three domains with horizontal resolution of 50 km are compared with ERA reanalysis and observed datasets to determine if there is an optimal RCM configuration with respect to domain size and the ability to reproduce important observed climate features in the Caribbean. Results are presented for the early wet season (May–July) and late wet season (August–October). There is a relative insensitivity to domain size for simulating some important features of the regional circulation and key rainfall characteristics e.g. the Caribbean low level jet and the mid summer drought (MSD). The downscaled precipitation has a systematically negative precipitation bias, even when the domain was extended to the African coast to better represent circulation associated with easterly waves and tropical cyclones. The implications for optimizing modelling efforts within resource-limited regions like the Caribbean are discussed especially in the context of the region’s participation in global initiatives such as CORDEX.

Seasonal water use by deciduous and evergreen woody species in a scrub community is based on water availability and root distribution

AbstractIn a seasonally dry plant community of central Florida, USA, that experiences water limitation in the dry season and high water availability in the wet season, we first tested whether evergreen woody species shift from shallow water in the wet season to deep water in the dry season. Second, we tested whether deciduous woody species restrict water uptake to the shallow soil during the wet season and cease water uptake during the dry season. To address these questions, we measured water source use of two deciduous and three evergreen species over 13 months using stable isotopes. As hypothesized in previous studies, we showed that leaflessness in deciduous plants is an important source of stem water isotopic fractionation. Therefore, we compared stable isotope ratios of stem water only when deciduous species had leaves and found that all species, except the evergreen Lyonia ferruginea, used proportionally the same water sources. Early dry season water use was based on water availability for all species except L. ferruginea, and deep soil (50–150 cm) was the most important water source. During the late dry and wet seasons, water uptake from each soil layer was based on its respective proportion of fine roots. Nevertheless, deep water remained an important water source throughout the year. This study clearly demonstrates the limitations of using stable isotopes of stem water when comparing deciduous versus evergreen species. Further, this study is the first to directly quantify depth of water uptake via isotope analysis and couple these findings with root distribution. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Assessing Nitrogen-Saturation in a Seasonally Dry Chaparral Watershed: Limitations of Traditional Indicators of N-Saturation

To evaluate nitrogen (N) saturation in xeric environments, we measured hydrologic N losses, soil N pools, and microbial processes, and developed an N-budget for a chaparral catchment (Sierra Nevada, California) exposed to atmospheric N inputs of approximately 8.5 kg N ha−1 y−1. Dual-isotopic techniques were used to trace the sources and processes controlling nitrate (NO3 −) losses. The majority of N inputs occurred as ammonium. At the onset of the wet season (November to April), we observed elevated streamwater NO3 − concentrations (up to 520 µmol l−1), concomitant with the period of highest gaseous N-loss (up to 500 ng N m−2 s−1) and suggesting N-saturation. Stream NO3 − δ15N and δ18O and soil N measurements indicate that nitrification controlled NO3 − losses and that less than 1% of the loss was of atmospheric origin. During the late wet season, stream NO3 − concentrations decreased (to <2 µmol l−1) as did gaseous N emissions, together suggesting conditions no longer indicative of N-saturation. We propose that chaparral catchments are temporarily N-saturated at ≤8.5 kg N ha−1 y−1, but that N-saturation may be difficult to reach in ecosystems that inherently leak N, thereby confounding the application of N-saturation indicators and annual N-budgets. We propose that activation of N sinks during the typically rainy winter growing season should be incorporated into the assessment of ecosystem response to N deposition. Specifically, the N-saturation status of chaparral may be better assessed by how rapidly catchments transition from N-loss to N-retention.

Diversity and altitudinal distribution of Chrysomelidae (Coleoptera) in Peregrina Canyon, Tamaulipas, Mexico.

The Chrysomelidae (Coleoptera) is a highly speciose family that has been poorly studied at the regional level in Mexico. In the present study, we estimated species richness and diversity in oak-pine forest, Tamaulipan thorny scrub and in tropical deciduous forests in Peregrina Canyon within the Altas Cumbres Protected Area of the northeastern state of Tamaulipas, Mexico. Sampling of Chrysomelidae consisted of five sweep net samples (200 net sweeps) within each of three sites during four sample periods: early dry season, late dry season, early wet season, and late wet season. Species were identified and total numbers per species were recorded for each sample. A total of 2,226 specimens were collected belonging to six subfamilies, 81 genera and 157 species of Chrysomelidae from the study area. Galerucinae was the most abundant subfamily with 1,828 specimens, representing 82.1% of total abundance in the study area. Lower abundance was recorded in Cassidinae (8.5%), Eumolpinae (3.6%), Cryptocephalinae (2.2%), Chrysomelinae (2.2%), and finally Criocerinae (1.3%). The highest species richness was also presented in the subfamily Galerucinae with 49% of the total obtained species followed by Cassidinae (20%), Cryptocephalinae (9.7%), Eumolpinae (9.7%), Chrysomelinae (6.5%) and Criocerinae (5.2%). The most common species were Centralaphthona fulvipennis Jacoby (412 individuals), Centralaphthona diversa (Baly) (248), Margaridisa sp.1 (219), Acallepitrix sp.1 (134), Longitarsus sp.1 (104), Heterispa vinula (Erichson) (91), Epitrix sp.1 (84) and Chaetocnema sp.1 (72). Twenty-two species were doubletons (1.97% of total abundance) and 52 were singletons (2.33%). The estimated overall density value obtained was 0.0037 individuals/m2. The greatest abundance and density of individuals were recorded at the lowest elevation site. However, alpha diversity increased with increasing altitude. Similarity values were less than 50% among the three sites indicating that each site had distinct species assemblages of Chrysomelidae. The highest abundance was obtained during the late dry season, whereas diversity indices were highest during the early wet season. The present work represents the first report of the altitudinal variation in richness, abundance, and diversity of Chrysomelidae in Mexico. These results highlight the importance of conservation of this heterogeneous habitat and establish baseline data for Chrysomelidae richness and diversity for the region.

Seasonal Change of Species Diversity Patterns of Non‐volant Small Mammals along Three Subtropical Elevational Gradients

AbstractOur understanding of geographic patterns of species diversity and the underlying mechanisms is increasing rapidly, whereas the temporal variation in these patterns remains poorly understood. We examined the seasonal species richness and species turnover patterns of non‐volant small mammals along three subtropical elevational gradients in southwest China. Small mammal diversity was surveyed in two seasons (early wet season and late wet season) using a standardized sampling protocol. The comparison of species richness patterns between two seasons indicated a temporal component in magnitude and shape, with species richness at high elevations clearly increased during the late wet season. Species richness demonstrated weak correlations with modelled temperature and precipitation. The elevational pattern of species turnover measured by Chao‐Sørenson similarity index also changed seasonally, even though the temporal pattern varied with scale. Species turnover between neighboring elevations at high elevations was slower in the late wet season. Meanwhile, there was an acceleration of species turnover along the whole range of the gradient. The seasonal change in species diversity patterns may be due to population‐level increases in abundance and elevational migration, whereas seasonal variation in factors other than temperature and precipitation may play a greater role in driving seasonal diversity patterns. Our study strongly supports the seasonality in elevational patterns of small mammal diversity in subtropical montane forests. Thus it is recommended that subsequent field surveys consider temporal sampling replicate for elevational diversity studies.

English

Effects of season, browse species and polyethylene glycol (PEG) on in vitro digestibility of five plant species from sub-humid subtropical savannah of South Africa were investigated. Leaves of Acacia natalitia, Acacia nilotica, Dichrostachys cinerea, Scutia myrtina and Chromolaena odorata were harvested during dry (June/July), early wet (November/December) and late wet (February/March) seasons. An in vitro technique (72 h incubating time) was used in two experiments carried out with nine replicates (3 runs x 3 replicates). Experiment 1, tested the effects of season and browse species, while Experiment 2, tested the effect of condensed tannins using PEG (4000) on an in vitro degradability of the forages. Season and species affected the true degradability (TrDeg), short chain fatty acids (SCFA) and partitioning factor (PF). TrDeg ranged from 684 to 856 g/kg dry matter (DM). Total SCFA varied (P&lt;0.05) among seasons and browse species. Addition of PEG decreased TrDeg and PF but increased total SCFA. Results suggested these browse species have potential to be used as feed supplements. Key words: Tannin-rich species, tannins, true degradability, short chain fatty acid.

Growth and Yield Performance of Cowpea (Vigna Unguiculata (L.) Walp) as influenced by Row-Spacing and Period of Weed interference in South-West Nigeria

Weed problem appears to be the most deleterious factor causing between 25 and 60% reduction in potential yield of cowpea. Field trials were therefore conducted to study the effect of inter-row spacing and period of weed interference on growth and yield of cowpea (Vigna unguiculata (L) Walp) at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta (07° 15'; 03° 25' E) in South Western Nigeria during the early and late wet seasons of 2009. The experiment consisted of eight main plots of weed interference which included initial weed removal for 3, 6, 9, and 12 weeks after sowing (WAS) and subsequently weed –infested until harvest as well as initial weed infestation for corresponding periods and thereafter kept weed free until harvest. There were also sub-plot treatments of three inter-row spacing of 60, 75, and 90 cm. All treatments in different combinations were laid out in a split-plot design with three replications. In both trials, the use of inter-row spacing of 60 cm resulted in significant reduction in weed growth as evident in lower weed dry matter production and subsequent higher cowpea pod and grain yields than those of 75 and 90 cm inter-row spacing. Initial weed infestation of up to 3 WAS did not have any adverse effect on crop growth and cowpea grain yields provided the weeds were subsequently removed. On the other hand, cowpea grain yield loss was not significantly averted by keeping the crop weed free for only 3 WAS without subsequent weed removal. In this study, initial weed-infestation for 6 WAS and beyond significantly depressed various crop growth parameter and cowpea grain yield compared with the crop kept weed free throughout its life cycle. In order to obtain optimum yields similar to that of the weed free cowpea field, it was required to keep the crop weed free for 6 WAS and beyond. However, frequent weeding beyond 9 weeks after sowing did not improve cowpea yield significantly and as a matter of fact it may even result in reduction of cowpea grain yield due to mechanical damage of hoe weeding. The practical implication of this finding is that early weeding starting from 3 WAS is very crucial for cowpea production while the critical period of weed removal for optimum yield in cowpea is between 3 and 9 WAS in the forest-savannah transitional zone of south Western Nigeria.

What controls the interannual variation of the wet season onsets over the Amazon?

AbstractPrevious studies have established that sea surface temperature anomalies (SSTAs) in the tropical Pacific and Atlantic are the main forcing of the interannual variation of the wet season onsets in the Amazon. However, this variation appears to be complex and not uniquely determined by SSTAs. What causes such a complexity and to what extent the interannual variation of the wet season onsets is predictable remain unclear. This study suggests that such a complex relationship is the result of several competing processes, which are nonlinearly related to the SSTAs. In particular, three dry season conditions are crucial for determining interannual variation of the wet season onset. (i) A poleward shift of the Southern Hemisphere subtropical jet (SHSJ) over the South American sector, initiated from a wave train‐like structure possibly forced by south central Pacific SST patterns, can prevent cold frontal systems from moving northward into the Amazon. This delays cold air incursion and results in late wet season onset over the southern Amazon. (ii) An anomalous anticyclonic center, which enhances westerly wind at 850 hPa over the southern Amazon and also the South American low‐level jets, leads to moisture export from the southern Amazon to La Plata basin and reduces convective systems that provide elevated diabatic heating. (iii) Smaller convective available potential energy (CAPE) limits local thermodynamically driven convection. Based on the stepwise and partial least squares regressions, these three selected preseasonal conditions (Niño 4, SHSJ, and CAPE) can explain 57% of the total variance of the wet season onset.

Effects of Time of Weed Removal and Cropping system on Weed Control and Crop Performance in Okra/Amaranthus Intercrop

A field trial w as conducted during the late wet seasons of 2011 and 2012 at the Research Farm of the Federal University of Agriculture, Alabata, Abeokuta (7015 �N, 3025 �E) in the forest savanna-transition zone of Ogun State, South Western Nigeria. The objective was to evaluate the effect of time of weed removal and cropping system on weed control and crop performance in okra/amaranthus intercrop. The experiment was laid out in a Randomized Complete Block Design (RCBD) in a Split-plot arrangement.The treatments consisted of three main plots and five su b plots replicated three times. The main plot treatments were single hoe-weeding at 3 weeks after planting (WAP), double weeding at 3 & 6 WAP and no weeding, while the sub plots consisted of okra intercropped wit h amaranthus at 0.5g/m2or 1.0g/m2, okra sand amaranthus sole at0.5g/m2 or 1.0g/m2. Results from the study showed that intercropping of okra with amaranthus reduced weed infestation significantly (p<0.05) compared to sole okra. Weed control treatments significantly (p<0.05) reduced weed infestation in the intercrop while cropping system did not have any significant effect (p<0.05) on the weed biomass, plant height, pod length, number of pods and pod fresh weight. Uncontrolled weed infesta tion led to 50.7 % yield loss in okra. It is therefore concluded that intercropping of okra with amaranthus is an effective means of reducing weed pressure in okra production as well as increasing land productivity.

Serum Copper and Haematological Values of Sheep of Different Physiological Stages in the Dry and Wet Seasons of Central Trinidad

A study was conducted to determine serum copper (Cu) concentrations and hematological values of 174 sheep from four medium sized farms, pertaining to physiological stage, in the late dry and late wet seasons of Central Trinidad. Serum Cu was significantly lower in the dry than in the wet season (P < 0.001) with a corresponding high percentage of samples with low Cu levels in the former. 31% of dry nonpregnant sheep exhibited a nonregenerative anaemia. Also, hemoglobin and packed cell volume values varied (P < 0.001) including lymphocyte (P < 0.01) counts, among growing animals compared with other physiological stages. Significant variations also occurred among neutrophil (P < 0.05) and eosinophil (P < 0.05) values in sheep. Highest haemoglobin and packed cell volume, white blood cell counts, and lymphocyte values in growing sheep compared with other stages were probably age related.

Effect of Seasons on the Reproductive Performance of Bovan Nera and Isa Brown Parent-stock Chickens in a Hot Humid Environment

Seasons play an important role in the performance of breeder chickens, but lack of adequate records on its specific effects in specific seasons could influence the efforts of breeders to improve on local ecotypes of chicken for standardization into breeds. This is why Nigeria still depends mainly on imported breeds of chicken for commercial production of chicken. In this study, the influence of Early Wet (EW), Late Wet (LW) and Early Dry (ED) and Late Dry (LD) seasons on reproductive parameters of Bovan Nera (BN) and Isa Brown (IB) parent-stock chickens were studied in the humid South-West Nigeria. Ten-year data on both genotypes were obtained from Ajanla Farms Hatchery Ibadan and analysed for Eggs Set (ES), Egg Fertility (EF), Egg Hatchability (EH), Pullet Day-old Chicks (PDC) and Hatching Rejects (HR) to study the effect of seasons on these parameters. ANOVA (p<0.05) showed that seasons have significant influence on EF, EH and HR in BN; and ES, EH and HR in IB. Late wet season gave the best results on reproduction thus making it potentially the most favorable season for hatching activities in both genotypes, and therefore may signal good fortune in commercial chicks production enterprises of breeder chickens in hot humid regions.

Temporal Patterns of Abundance of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and Mitochondrial DNA Analysis of Ae. albopictus in the Central African Republic

The invasive Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) was first reported in central Africa in 2000, in Cameroon, with the indigenous mosquito species Ae. aegypti (Diptera: Culicidae). Today, this invasive species is present in almost all countries of the region, including the Central African Republic (CAR), where it was first recorded in 2009. As invasive species of mosquitoes can affect the distribution of native species, resulting in new patterns of vectors and concomitant risk for disease, we undertook a comparative study early and late in the wet season in the capital and the main cities of CAR to document infestation and the ecological preferences of the two species. In addition, we determined the probable geographical origin of invasive populations of Ae. albopictus with two mitochondrial DNA genes, COI and ND5. Analysis revealed that Ae. aegypti was more abundant earlier in the wet season and Ae. albopictus in the late wet season. Used tyres were the most heavily colonized productive larval habitats for both species in both seasons. The invasive species Ae. albopictus predominated over the resident species at all sites in which the two species were sympatric. Mitochondrial DNA analysis revealed broad low genetic diversity, confirming recent introduction of Ae. albopictus in CAR. Phylogeographical analysis based on COI polymorphism indicated that the Ae. albopictus haplotype in the CAR population segregated into two lineages, suggesting multiple sources of Ae. albopictus. These data may have important implications for vector control strategies in central Africa.

Social factors affecting seasonal variation in bovine trypanosomiasis on the Jos Plateau, Nigeria

BackgroundAfrican Animal Trypanosomiasis (AAT) is a widespread disease of livestock in Nigeria and presents a major constraint to rural economic development. The Jos Plateau was considered free from tsetse flies and the trypanosomes they transmit due to its high altitude and this trypanosomiasis free status attracted large numbers of cattle-keeping pastoralists to the area. The Jos Plateau now plays a major role in the national cattle industry in Nigeria, accommodating approximately 7% of the national herd, supporting 300,000 pastoralists and over one million cattle. During the past two decades tsetse flies have invaded the Jos Plateau and animal trypanosomiasis has become a significant problem for livestock keepers. Here we investigate the epidemiology of trypanosomiasis as a re-emerging disease on the Plateau, examining the social factors that influence prevalence and seasonal variation of bovine trypanosomiasis.MethodsIn 2008 a longitudinal two-stage cluster survey was undertaken on the Jos Plateau. Cattle were sampled in the dry, early wet and late wet seasons. Parasite identification was undertaken using species-specific polymerase chain reactions to determine the prevalence and distribution of bovine trypanosomiasis. Participatory rural appraisal was also conducted to determine knowledge, attitudes and practices concerning animal husbandry and disease control.ResultsSignificant seasonal variation between the dry season and late wet season was recorded across the Jos Plateau, consistent with expected variation in tsetse populations. However, marked seasonal variations were also observed at village level to create 3 distinct groups: Group 1 in which 50% of villages followed the general pattern of low prevalence in the dry season and high prevalence in the wet season; Group 2 in which 16.7% of villages showed no seasonal variation and Group 3 in which 33.3% of villages showed greater disease prevalence in the dry season than in the wet season.ConclusionsThere was high seasonal variation at the village level determined by management as well as climatic factors. The growing influence of management factors on the epidemiology of trypanosomiasis highlights the impact of recent changes in land use and natural resource competition on animal husbandry decisions in the extensive pastoral production system.

Do we need to understand microbial communities to predict ecosystem function? A comparison of statistical models of nitrogen cycling processes

Despite the central role of microorganisms in biogeochemistry, process models rarely explicitly account for variation in communities. Here, we use statistical models to address a fundamental question in ecosystem ecology: do we need to better understand microbial communities to accurately predict ecosystem function? Nitrogen (N) cycle process rates and associated gene abundances were measured in tropical rainforest soil samples collected in May (early wet season) and October (late wet season). We used stepwise linear regressions to examine the explanatory power of edaphic factors and functional gene relative abundances alone and in combination for N-cycle processes, using both our full dataset and seasonal subsets of the data. In our full dataset, no models using gene abundance data explained more variation in process rates than models based on edaphic factors alone, and models that contained both edaphic factors and community data did not explain significantly more variation in process rates than edaphic factor models. However, when seasonal datasets were examined separately, microbial predictors enhanced the explanatory power of edaphic predictors on dissimilatory nitrate reduction to ammonium and N2O efflux rates during October. Because there was little variation in the explanatory power of microbial predictors alone between seasonal datasets, our results suggest that environmental factors we did not measure may be more important in structuring communities and regulating processes in October than in May. Thus, temporal dynamics are key to understanding the relationships between edaphic factors, microbial communities and ecosystem function in this system. The simple statistical method presented here can accommodate a variety of data types and should help prioritize what forms of data may be most useful in ecosystem model development.