Estimated Financial Impact of Trypanosoma vivax on the Brazilian Pantanal and Bolivian Lowlands

The financial impact of the first outbreak of Trypanosoma vivax in the Brazilian Pantanal wetland is estimated. Results are extended to include outbreaks in the Bolivian lowlands providing a notion of the potential influence of the disease and an analytical basis. More than 11 million head of cattle, valued at more than US$3 billion are found in the Brazilian Pantanal and Bolivian lowlands. The total estimated cost of the 1995 outbreak of T. vivax is the sum of the present values of mortality, abortion, and productivity losses and treatment costs, or about 4% of total brood cow value on affected ranches. Had the outbreak gone untreated, the estimated losses would have exceeded 17% of total brood cow value.

Linking soil properties and pre-Columbian agricultural strategies in the Bolivian lowlands: The case of raised fields in Exaltación

This paper aims to further our understanding of pre-Columbian agricultural systems in the Llanos de Moxos, Bolivia. Three different types of raised fields co-existing in the same site near the community of Exaltación, in north-western Beni, were studied. The morphology, texture and geochemistry of the soils of these fields and the surrounding area were analysed. Differences in field design have often been associated with the diversity of cultural practices. Our results suggest that in the study area differences in field shape, height and layout are primarily the result of an adaptation to the local edaphology. By using the technology of raised fields, pre-Columbian people were able to drain and cultivate soils with very different characteristics, making the land suitable for agriculture and possibly different crops. This study also shows that some fields in the Llanos de Moxos were built to prolong the presence of water, allowing an additional cultivation period in the dry season and/or in times of drought. Nevertheless, the nature of the highly weathered soils suggests that raised fields were not able to support large populations and their management required long fallow periods.

Fire, climate and vegetation linkages in the Bolivian Chiquitano Seasonally Dry Tropical Forest

South American seasonally-dry tropical forests (SDTF) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12,000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8,000 and 7,000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined, but severe regional droughts persisted through the mid-Holocene, SDTF, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTF are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime.

Human-environment interactions in pre-Columbian Amazonia: The case of the Llanos de Moxos, Bolivia

The reconstruction of past environmental and historical events is much needed in Amazonia, a region at the centre of heated debates about the extent of pre-Columbian human disturbance of the natural ecosystems. Important aspects of this debate are to establish to what extent the rise of social complexity was influenced by the local geo-ecology; and what productive strategies were adopted in order to sustain these societies. The Llanos de Moxos (LM), in the Bolivian Amazon, is a vast floodplain made up of a variety of geo-ecological sub regions that host many different types of pre-Columbian earthworks. Therefore, it offers an excellent opportunity to compare different kinds of archaeological landscapes and their relationship to different pre-Columbian cultures and environmental settings. This paper analyses the links between pre-Columbian earthworks and the local geo-ecology in two regions of the LM: 1) the platform field region (PFR) in the north of Santa Ana de Yacuma, where the highest concentration of raised fields has been documented, and 2) the monumental mounds region (MMR) south and east of Trinidad, where >100 pre-Columbian monumental mounds are found. The study draws from remote sensing and GIS analysis, field work in the Bolivian lowlands, and laboratory analysis. Differences in the way people transformed the landscape in the PFR and MMR seem to respond to differences in the local geo-ecology of the two sites. The results also suggest that environmental conditions exerted an important, though not exclusive, control over the levels of social complexity that were reached in different areas of the LM.

Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region’s past and offers a new context within which the late Holocene “Earthmovers” of the Llanos de Moxos could have emerged.

Yield response of rice (Oryza sativa L.) genotypes to different types of drought under rainfed lowlands - Part 1. Grain yield and yield components

Responses of rice genotypes to drought stress may be different when characteristics of the drought stress environments differ. The performance of 128 genotypes was examined under irrigation and four different types of drought stress, to determine genotypic consistency in yield and factors determining yields under different drought stress conditions. The different drought conditions were mild drought during grain filling, short and severe drought at flowering, prolonged severe drought during the reproductive to grain filling, and prolonged mild drought during vegetative and grain filling. Genotypic grain yield under mild stress conditions was associated with yield under irrigated conditions, indicating the importance of potential yield in environments where the yield reduction was less than 50%. However, yields under irrigated conditions differed over time and locations. Under prolonged or severe drought conditions, flowering time was an important determinant of grain yield. Earlier flowering genotypes escaped the severe stress and had higher grain yields indicating large genotype by environment (G x E) interactions which have implications for plant breeding even for mild stress. It is suggested that variations in flowering time, potential yields and drought patterns need to be considered for development of drought-resistant cultivars using specific physiological traits. (C) 2002 Elsevier Science B.V. All rights reserved.

Yield response of rice (Oryza sativa L.) genotypes to different types of drought under rainfed lowlands - Part 2. Selection of drought resistant genotypes

Drought frequently reduces grain yield of rainfed lowland rice. A series of experiments were conducted in drought-prone northeast Thailand to study the magnitude and consistency of yield responses of diverse, rainfed lowland rice genotypes to drought stress environments and to examine ways to identify genotypes that confer drought resistance. One hundred and twenty-eight genotypes were grown under non-stress and four different types of drought stress conditions. The relationship of genotypic variation in yield under drought conditions to genetic yield potential, flowering time and flowering delay, and to a drought response index (DRI) that removed the effect of potential yield and flowering time on yield under stress was examined. Drought stress that developed prior to flowering generally delayed the time of flowering of genotypes, and the delay in flowering was negatively associated with grain yield, fertile panicle percentage and filled grain percentage. Genotypes with a longer delay in flowering time had extracted more water during the early drought period, and as a consequence, had higher water deficits. They were consistently associated with a larger yield reduction under drought and in one experiment with a smaller DRI. Genotypes, however, responded differently to the different drought stress conditions and there was no consistency in the DRI estimates for the different genotypes across the drought stress experiments. The results indicate that with the use of irrigated-control and drought test environments, genotypes with drought resistance can be identified by using DRI or delay in flowering. However, selections will differ depending on the type of drought condition. The inconsistency of the estimates in DRI and flowering delay across different drought conditions reflects the nature of the large genotype-by-environment interactions observed for grain yield under various types of drought in rainfed lowland conditions. (C), 2002 Elsevier Science B.V. All rights reserved.

Yield response of rice (Oryza sativa L.) genotypes to different types of drought under rainfed lowlands - Part 3. Plant factors contributing to drought resistance

A series of experiments were conducted in drought-prone northeast Thailand to examine the magnitude of yield responses of diverse genotypes to drought stress environments and to identify traits that may confer drought resistance to rainfed lowland rice. One hundred and twenty eight genotypes were grown under non-stress and four different types of drought stress conditions. Under severe drought conditions, the maintenance of PWP of genotypes played a significant role in determining final grain yield. Because of their smaller plant size (lower total dry matter at anthesis) genotypes that extracted less soil water during the early stages of the drought period, tended to maintain higher PWP and had a higher fertile panicle percentage, filled grain percentage and final grain yield than other genotypes. PWP was correlated with delay in flowering (r = -0.387) indicating that the latter could be used as a measure of water potential under stress. Genotypes with well-developed root systems extracted water too rapidly and experienced severe water stress at flowering. RPR which showed smaller coefficient of variation was more useful than root mass density in identifying genotypes with large root system. Under less severe and prolonged drought conditions, genotypes that could achieve higher plant dry matter at anthesis were desirable. They had less delay in flowering, higher grain yield and higher drought response index, indicating the importance of ability to grow during the prolonged stress period. Other shoot characters (osmotic potential, leaf temperature, leaf rolling, leaf death) had little effect on grain yield under different drought conditions. This was associated with a lack of genetic variation and difficulty in estimating trait values precisely. Under mild stress conditions (yield loss less than 50%), there was no significant relationship between the measured drought characters and grain yield. Under these mild drought conditions, yield is determined more by yield potential and phenotype than by drought resistant mechanisms per se. (C) 2002 Elsevier Science B.V. All rights reserved.

Leaf litter decomposition of Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea

No information is available on the decomposition and nutrient release pattern of Piper aduncum and Imperata cylindrica despite their importance in shifting cultivation systems of Papua New Guinea and other tropical regions. We conducted a litter bag study (24 weeks) on a Typic Eutropepts in the humid lowlands to assess the rate of decomposition of Piper aduncum, Imperata cylindrica and Gliricidia sepium leaves under sweet potato (Ipomoea batatas). Decomposition rates of piper leaf litter were fastest followed closely by gliricidia, and both lost 50% of the leaf biomass within 10 weeks. Imperata leaf litter decomposed much slower and half-life values exceeded the period of observation. The decomposition patterns were best explained by the lignin plus polyphenol over N ratio which was lowest for piper (4.3) and highest for imperata (24.7). Gliricidia leaf litter released 79 kg N ha(-1), whereas 18 kg N ha(-1) was immobilised in the imperata litter. The mineralization of P was similar for the three species, but piper litter released large amounts of K. The decomposition and nutrient release patterns had significant effects on the soil. The soil contained significantly more water in the previous imperata plots at 13 weeks due to the relative slow decomposition of the leaves. Soil N levels were significantly reduced in the previous imperata plots due to immobilisation of N. Levels of exchangeable K were significantly increased in the previous piper plots due to the large addition of K. It can be concluded that piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato. Gliricidia leaf litter contained much N, whereas imperata leaf litter releases relatively little nutrients and keeps the soil more moist. Gliricidia fallow is more attractive than an imperata fallow for it improves the soil fertility and produces fuelwood as additional saleable products.

Prevalence of human papillomavirus infection in rural villages of the Bolivian Amazon

Cervical cancer constitutes a major health problem in developing countries like Bolivia. The roles of certain genotypes of human papillomaviruses (HPVs) in the pathogenesis of cervical cancer is well established. The prevalence of HPV infection among sexually active women varies greatly. Information regarding HPV infection in Bolivia is very much scarce, specially in regions like the Amazonian lowland. We studied 135 healthy women living in four rural localities of the Bolivian Amazon. Presence of HPV in DNA extracted from cervical swabs was analyzed using a reverse line hybridization assay. The estimated overall HPV infection prevalence among the studied rural localities was 5.9% (ranging from 0-16.6%). These values were unexpectedly low considering Bolivia has a high incidence of cervical cancer. The fact that Amazonian people seem to be less exposed to HPV, makes it likely that some other risk factors including host lifestyle behaviors and genetic background may be involved in the development of cervical cancer in this population.

NEW Stylogaster AND RANGES OF CONOPIDAE (DIPTERA) FROM THE BRAZILIAN AND BOLIVIAN AMAZONIA

Conopid flies from the collection of the Instituto Nacional de Pesquisas da Amazonia, Manaus, Brazil, are examinied, of which two from Brazil are new, Stylogaster rafaelifrom Rondônia and S. ctenitarsafrom Roraima. This data, along with new material from Bolivia, expands the distributions of thirteen species of Conopidae. Figures for S. rafaelisp.n. and S. ctenitarsasp.n. are included.

The vulnerability to pollution and hydrochemical variation of eleven springs (catchments) in the karst lowlands of the west of Ireland

The vulnerability to pollution and hydrochemical variation of groundwater in the mid-west karstic lowlands of Ireland were investigated from October 1992 to September 1993, as part of an EU STRIDE project at Sligo Regional Technical College. Eleven springs were studied in the three local authority areas of Co. Galway, Co. Mayo, and Co. Roscommon. Nine of the springs drain locally or regionally important karstic aquifers and two drain locally important sand and gravel aquifers. The maximum average daily discharge of any of the springs was 16,000 m3/day. Determination of the vulnerability of groundwater to pollution relies heavily on an examination of subsoil deposits in an area since they can act as a protecting or filtering layer over groundwater. Within aquifers/spring catchments, chemical reactions such as adsorption, solution-precipitation or acid-base reactions occur and modify the hydrochemistry of groundwater (Lloyd and Heathcote, 1985). The hydrochemical processes) that predominate depend cm the mineralogy of the aquifer, the hydrogeological environment, the overlying subsoils, and the history of groundwater movement. The aim of this MSc research thesis was to investigate the hydrochemical variation of spring outflow and to assess the relationship between these variations and the intrinsic vulnerability of the springs and their catchments. If such a relationship can be quantified, then it is hoped that the hydrochemical variation of a spring may indicate the vulnerability of a spring catchment without the need for determining it by field mapping. Such a method would be invaluable to any of the three local authorities since they would be able to prioritise sources that are most at risk from pollution, using simple techniques of chemical sampling, and statistical analysis. For each spring a detailed geological, hydrogeological and hydrochemical study was carried out. Individual catchment areas were determined with a water balance/budget and groundwater tracing. The subsoils geology for each spring catchment were mapped at the 1:10,560 scale and digitised to the 1:25,000 scale with AutoCad™ and Arclnfo™. The vulnerability of each spring was determined using the Geological Survey's vulnerability guidelines. Field measurements and laboratory based chemistry analyses of the springs were undertaken by personnel from both the EPA Regional Laboratory in Castlebar, Co. Mayo, and the Environment Section of Roscommon Co. Council. Electrical conductivity and temperature (°C) were sampled fortnightly, in the field, using a WTW microprocessor conductivity meter. A percentage (%) vulnerability was applied to each spring in order to indicate the areal extent of the four main classes of vulnerability (Extreme, High, Moderate, and Low) which occurred within the confines of each spring catchment. Hydrochemical variation for the springs were presented as the coefficient of variation of electrical conductivity. The results of this study show that a clear relationship exists between the degree of vulnerability of each catchment area as defined by the subsoil cover and the coefficient of variation of EC, with the coefficient of variation increasing as the vulnerability increases. The coefficient of variation of electrical conductivity is considered to be a parameter that gives a good general reflection of the degree of vulnerability occurring in a spring catchment in Ireland's karstic lowlands.