L'apport de matière particulaire fluviale (MPF) aux eaux naturelles joue un rôle essentiel dans le cycle global des éléments et influence le cycle du carbone organique (Corg) de deux façons: 1°, les MPF comprennent une source importante d'éléments nutritifs qui peuvent augmenter la production primaire dans les océans. Par exemple, le flux global de MPF de nutriments tels que Si, P et Fe dépasse son flux dissous par des facteurs de 50, 100 et 350. 2°, l'apport de MPF des continents aux océans est un contrôle majeur de la séquestration du Corg, un processus essentiel dans la réduction du CO2 à long terme par le cycle de Corg. Pour explorer le lien entre l'apport de MPF et la production primaire dans les eaux naturelles, une série d'expériences de croissance a été réalisée impliquant deux producteurs primaires abondants: la cyanobactérie d'eau douce Synechococcus sp. (SYN), et la diatomée marine Thalassiosira weissflogii (TW). Des expériences ont été réalisées en présence et en l'absence de différentes MPF et à différents niveaux nutritifs initiaux. Les résultats démontrent que les MPF augmentent nettement la croissance de la biomasse en fonction de la concentration du MPF. Dans les expériences menées avec la cyanobactérie SYN, la présence de MPF a 1) déclenché une croissance bactérienne dans des conditions pourtant défavorables, 2) augmenté la concentration totale de biomasse et 3) déclenché une croissance bactérienne même après la consommation des nutriments initiaux. L'effet positif des MPF sur la croissance de la diatomée marine TW a été le plus évident pour les expériences n'impliquant pas de nutriments, où les diatomées se sont multipliées linéairement en présence de MPF alors que ces cultures sont mortes en absence des MPF. De plus, des études MEB ont montré un contact physique direct entre les microbes ou les substances organiques excrétées par les microbes et les MPF. Conformément aux travaux issus de la littérature, nous suggérons que les microbes peuvent acquérir des nutriments directement à partir des minéraux, ce qui augmenterait le potentiel des MPF en tant que source de nutriments. Le contact direct suggère aussi une augmentation de l'efficacité de piégeage du Corg par l'augmentation 1) du contenu de Corg absorbé sur les surfaces minérales, 2) de l'agglomération des particules organiques et inorganiques et donc la formation de neige marine ou 3) des vitesses de chute de Corg par "mineral ballasting". La fixation directe des microbes sur les surfaces minérales a également été observée dans les échantillons naturels obtenus au cours d'une étude de terrain sur la côte sud islandaise. Dans l'ensemble, cette étude fournit des preuves expérimentales de l'importance des MPF dans le cycle de Corg grâce à son impact sur la production primaire. En outre, ces travaux rassemblent des preuves que les MPF peuvent faciliter l'inhumation de Corg grâce à la fixation de microbes sur les surfaces ou à la formation des agglomérats minéraux- microbes qui chutent rapidement dans la colonne d´eau. Des études complémentaires ont été effectuées pour évaluer la qualité des compositions isotopiques du carbone, afin de préserver les estimations des taux de séquestration du Corg à travers une période géologique donnée. Les variations du degré de production primaire et du piégeage du Corg au cours des temps géologiques sont conservées dans la signature isotopique du C des carbonates. L'utilisation de ces signatures pour reconstruire les conditions environnementales passées exige cependant que ces signatures soient conservées pour des vastes échelles de temps. Les résultats expérimentaux démontrent que la composition isotopique du C de la calcite évolue continuellement vers l'équilibre isotopique entre les fluides et les minéraux. Cette observation suggère que les compositions isotopiques de C dans la calcite pourraient changer notablement si la calcite était constamment dans un déséquilibre isotopique avec son fluide coexistant. / The supply of riverine particulate material (RPM) to natural waters plays a vital role in the global cycle of the elements and is considered to influence the organic carbon cycle in two ways. First, RPM comprise a vast source of nutrients which can increase primary production in the oceans. For example, the global RPM flux of nutrients such as Si, P and Fe exceeds its corresponding dissolved flux by factors of 50, 100 and 350. Second, the supply of RPM to the oceans is a major control of organic matter (Corg) burial, an essential process in the long term CO2 drawdown via the organic pathway. To explore the link between RPM supply and primary production in natural waters, a series of microcosm growth experiments was performed with two common primary producing microbes, the freshwater cyanobacteria Synechococcus sp. and the marine diatom Thalassiosira weissflogii. Experiments were performed in the presence and absence of different RPM at different initial nutrient levels. Results demonstrate that RPM significantly increase bacterial biomass growth as a function of RPM concentration. Notably, in experiments conducted with the freshwater cyanobacteria Synechococcus sp., the presence of RPM 1) triggered bacterial growth in otherwise unfavorable conditions, 2) increased total biomass concentration, and 3) induced steady bacterial growth even after consumption of the initial nutrients. The positive effect of RPM on the growth of the marine diatom Thalassiosira weissflogii was most obvious in nutrient free experiments where cultures grew linearly with time in the presence of RPM, whereas these cultures died in RPM free controls. Furthermore, SEM investigations showed direct physical contact between microbes or microbially excreted organic substances and the particulates. In accord with reports in the literature, we suggest that microbes may acquire nutrients directly from the rock, which would again enhance the potential of RPM as source of limiting nutrients. The direct physical contact also suggests an increase in the burial efficiency of Corg through either 1) increasing Corg content absorbed on mineral surfaces, 2) increasing agglomeration and marine snow formation of organic and inorganic particles or 3) increasing organic matter settling velocities through mineral ballasting. The direct attachment of microbes on mineral surfaces was also observed in natural samples obtained from a field study at the Icelandic South coast. The positive effect of RPM on microbial growth and its effect on Corg burial are complimentary. Agglomeration is a function of suspended particle concentration, organic or inorganic. An elevated biomass concentration induced by the presence of RPM results in a high total suspended matter concentration, thus increasing the particle agglomeration rate. Taken together, this study provides experimental evidence for the importance of RPM in the organic C-cycle through its positive impact on primary production. Furthermore, it compiles evidence that particulates may facilitate organic matter burial through direct attachment of microbes on sediment surfaces or the formation of fast settling mineral/microbe agglomerations. Complimentary studies were performed to assess the quality of carbon isotope compositions to preserve estimates of Corg burial rates over geological time. Variations in the degree of primary production and Corg burial during Earths' history are recorded in the C-isotopic signature of marine carbonates. The use of carbon isotopic signatures in carbonates to reconstruct past environmental conditions, however, requires that these signatures are preserved over vast timescales. Experimental results demonstrate, that the carbon isotopic composition of calcite continuously evolves towards mineral-fluid isotopic equilibrium. This observation suggests that calcite C-isotopic compositions might change noticeably if the calcite were continuously in isotopic disequilibria with its co-existing fluid.

<p>Nutrient enrichment is the main cause of the increasing eutrophication process in the Baltic Sea during last century. A prerequisite counteract this process the load of nutrients to the Sea must be investigated. The large contribution of nutrients to the Sea is caused by emission from the rivers within the drainage basin. For the total emission of nutrient into the Sea the retention process in the rivers has big influence. This process in the river system has been assumed as a not important part of the nutrient cycle. However some investigators have pointed out that the retention process occurs in the river and be an important part of the nutrient dynamics in the river. For the object of investigation the Odra River Basin was chosen, as an example of a large river basin in the Baltic Sea Drainage Basin. The Odra River is mainly localized in Poland and contributes substantially to the eutrophication of the Baltic Proper. The Odra River is one of the least dammed major rivers of the Baltic Proper and as such of especial interest in retention studies. The phosphorus was chosen as an example of nutrient in the eutrophication process. The purpose of the investigation is to determine the phosphorus retention within the river. Two different models were used to calculate the retention process in the river. The"Multiple Regression Model"turned out to be insignificant, therefore the results were computed by using a “similarity model”, based on similarities between load from monitored tributary basins and the rest of the sub-basin. The retention in the Odra River in the amounted to -4608 t yr-1, which is 43% of the total phosphorus emission to the Odra River. There is also stated that in the Notec and the Warta rivers the retention process occur in the amount of -1940 t yr-1 and -3007 t yr-1 respectively.</p>

Nutrient enrichment is the main cause of the increasing eutrophication process in the Baltic Sea during last century. A prerequisite counteract this process the load of nutrients to the Sea must be investigated. The large contribution of nutrients to the Sea is caused by emission from the rivers within the drainage basin. For the total emission of nutrient into the Sea the retention process in the rivers has big influence. This process in the river system has been assumed as a not important part of the nutrient cycle. However some investigators have pointed out that the retention process occurs in the river and be an important part of the nutrient dynamics in the river. For the object of investigation the Odra River Basin was chosen, as an example of a large river basin in the Baltic Sea Drainage Basin. The Odra River is mainly localized in Poland and contributes substantially to the eutrophication of the Baltic Proper. The Odra River is one of the least dammed major rivers of the Baltic Proper and as such of especial interest in retention studies. The phosphorus was chosen as an example of nutrient in the eutrophication process. The purpose of the investigation is to determine the phosphorus retention within the river. Two different models were used to calculate the retention process in the river. The"Multiple Regression Model"turned out to be insignificant, therefore the results were computed by using a “similarity model”, based on similarities between load from monitored tributary basins and the rest of the sub-basin. The retention in the Odra River in the amounted to -4608 t yr-1, which is 43% of the total phosphorus emission to the Odra River. There is also stated that in the Notec and the Warta rivers the retention process occur in the amount of -1940 t yr-1 and -3007 t yr-1 respectively.

The United States Navy's involvement in the Vietnam War, especially its role in the region's inland waterways, has long been an overshadowed aspect of the conflict. Most histories ignore or minimize the Navy's contribution, especially its river patrol or 'brown water' role. Through archival and library research as well as interviews with U.S Navy Vietnam War veterans this thesis demonstrates the vital role played by the brown water navy in the northern provinces of South Vietnam. A key but understudied component of this effort was Task Force Clearwater, an improvised brown water fleet that-along with the maritime logistics campaign that it supported-would prove essential for the successful defense of South Vietnam's northernmost provinces and demonstrate the vital importance of inland naval power. Task Force Clearwater and its supported maritime logistics effort form a little explored component of the U.S. Navy's role in South Vietnam. A brown water task force that proved essential for the successful defense of the northern provinces of I Corps, Clearwater repeatedly demonstrated the vital importance of inland naval power and the critical need for reliable and protected routes of supply. The task force revealed many lessons that had been long understood, forgotten, and then relearned by the U.S. Navy, among them that control of inland waterways was perhaps the most advantageous form of logistical supply in war. Created in part to satisfy the ancient maxim of "keeping the supply lines open", the task force's role broadened with time. In the course of its existence the men and boats of Clearwater would provide not only the tools of war in I Corps but also provide key lessons for the future.

A multi-integrative approach was used to identify spatial and temporal relationships of natural and anthropogenic environmental variables affecting riverine ecosystem structure and function in the Athabasca Oil Sands Region (AOSR). A series of inter-related field studies were conducted to assess three key components of the freshwater food web (physico-chemical environment, basal productivity, benthic macroinvertebrates) utilizing an a priori environmental disturbance gradient experimental design. The gradient design was formulated to best discriminate the possible effects of natural and anthropogenic environmental variables on two river basins (Steepbank and Ells Rivers) each having different levels of oil sands (OS) land use disturbance. Findings from this study showed that natural variation explained most longitudinal and seasonal responses of physico-chemical environmental variables for both rivers, including possible mechanisms such as physical and chemical effects from the OS geological deposit and inputs from shallow groundwater upwelling. Basal productivity was likely controlled by natural variables within the Steepbank and Ells Rivers, such as potential OS deposit effects, nutrient availability and influences from turbidity and physical factors, with disturbance from OS development either negligible or not detected. Longitudinal and seasonal differences in benthic macroinvertebrate community composition were mostly related to natural variation, including possible mechanisms such as high discharge and sediment slump events on the Steepbank River, and community shifts from elevated metal concentrations from natural sources at upstream sites on the Ells River. This study demonstrated that developing baseline information on watersheds can be essential at discriminating sources of disturbance, with natural variation potentially confounding with anthropogenic factors. This study also highlights the need for further research to obtain an improved understanding of mechanistic pathways to better determine natural and anthropogenic non-point source disturbances and cumulative effects on the structure and function of tributary ecosystems in the AOSR at relevant spatial and temporal scales. / Graduate / 0329 / clsuzann@uvic.ca

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 245-266.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The ultimate goal of conservation planning is to ensure persistence of biodiversity. Biodiversity patterns and ecological processes are important aspects in conserving biodiversity. Although most researchers in conservation planning have focused on targeting biodiversity patterns, ecological and evolutionary processes can ensure persistence of biodiversity if incorporated into conservation planning. Ecological processes are the main drivers or sustainers of biodiversity. The aim of this research was to identify and map the spatial components of ecological processes in a portion of the Kavango Zambezi Transfrontier Conservation Area to aid in the implementation of biota movement corridors. Different methods have been used to identify suitable corridors but not much has been done on defining and mapping ecological processes that will ensure that the corridors maintain and generate biodiversity. A thorough literature survey was done to make a list of ecological processes that are important in maintaining the biodiversity in the area. Spatial components of ecological processes were mapped as surface elements aligned along linear environmental interfaces or gradients. The last part of the research was to suggest suitable movement corridors based on ecological processes. The results include five spatial components: riverine corridors, areas of high carbon sequestration, edaphic interfaces, upland-lowland interfaces and ecotones. Riverine corridors were mapped using a 1000 m buffer on either side of low lying rivers and 500 m buffer around rivers in the uplands. A map showing the carbon sequestration potential of vegetation in the study area was made using Moderate-Resolution Image Spectroradiometer (MODIS) derived NDVI data and the National Level Carbon Stock dataset done by the Woods Hole Research Center (WHRC) Pantropical. Edaphic interfaces were idenfied using by a 250 m buffer around contrasting soil types. Upland-lowland interfaces identified by a 250 m buffer along upland and lowland habitats. Classification of Landsat 8 was used to identify ecotones in the study area. The results of the spatial components were then compared with the habitat transformation map which shows populated areas. / AFRIKAANSE OPSOMMING: Die uiteindelike doel van bewaringsbeplanning is om voortbestaan van biodiversiteit te verseker. Biodiversiteitspatrone en ekologiese prosesse is belangrike aspekte in die bewaring van biodiversiteit. Alhoewel die meeste navorsers in bewaringsbeplanning fokus op teiken biodiversiteitspatrone, kan die voortbestaan van ekologiese en evolusionêre prosesse van biodiversiteit verseker word deur insluiting in bewaringsbeplanning. Ekologiese prosesse is die belangrikste drywers, of onderhouers, van biodiversiteit. Die doel van hierdie navorsing was dus om die ruimtelike komponente van ekologiese prosesse in 'n gedeelte van die Kavango Zambezi oorgrensbewaringsgebied te identifiseer en te karteer om te help met implementering van biota bewegingsdeurlope. Verskillende metodes is al gebruik om gepaste deurlope te identifiseer, maar min navorsing is gedoen oor definisie en kartering van ekologiese prosesse om te verseker dat die deurlope biodiversiteit sal onderhou en genereer. 'n Deeglike literatuurstudie is gedoen om 'n lys op te stel van ekologiese prosesse wat belangrik is in die handhawing van biodiversiteit in die gebied. Ruimtelike komponente van ekologiese prosesse is gekarteer as oppervlak elemente gebonde aan lineêre omgewingskoppelvlakke of gradiënte. Die laaste deel van die navorsing was om geskikte bewegingsdeurlope, gebaseer op ekologiese prosesse, voor te stel. Die resultate sluit vyf ruimtelike komponente in: rivierdeurlope, gebiede van hoë koolstofsekwestrasie, edafiese koppelvlakke, hoogland-Laeveld koppelvlakke en grensekotone. Rivierdeurlope is gekarteer met behulp van 'n 1000 meter buffer aan weerskante van laagliggende riviere en 500 meter buffer rondom riviere in die hooglande. ‘n Kaart wat die koolstofsekwestrasiepotensiaal van plantegroei in die studie area toon is gemaak met behulp van Moderate-Resolution Image Spectroradiometer (MODIS) afgeleide NDVI data en ʼn koolstofvoorraaddatastel (National Level Carbon Stock dataset) voorsien deur die Woods Hole Research Center (WHRC). Pantropiese edafiese koppelvlakke is geïdentifiseer met behulp van 'n 250 meter buffer rondom kontrasterende grondtipes. Hoogland-Laeveld koppelvlakke is geïdentifiseer deur 'n 250 meter buffer langs die berg en laagland habitatte. Klassifikasie van Landsat 8 data is gebruik om ekotone in die studie area te identifiseer. Die resultate van die ruimtelike komponente is vergelyk met die habitattransformasiekaart wat bevolkte gebiede toon.

This study investigates the experiences of the inhabitants of the lower region of the São Francisco River Basin, which has been badly affected by changes in the behaviour of the river in recent decades. An attempt was made to find out about the daily lives of these people who are mostly fishermen and masters of vernacular boats, by having conversations with them and observing their everyday lives. With regard to the construction sites, special attention was given to the dockyards which are makeshift buildings on the waterfront and designed to support the activities carried out there. The theory of drift, as well as the production of a log book and conceptual objects, served as methodological tools that could be applied to convey and interpret the atmosphere of the place. This made it possible to adapt to a scene that was so different from the academic world, while at the same time, influencing the way that the dissertation was undertaken. Thus, a narrative about the riverside environment was guided by a confrontation between oral history and the observations and interpretation made by the researcher of the features outlined in the familiar landscape of the workers on the river bank and subsequently explored through cartographic reflections. The study was supplemented by a desconstruction of the traditional map in the concept of the rhizome, where smooth and striated spaces were key features. In a time when a good deal of discussion has centred on the intangible heritage, experience of the riverside activities has made it possible to broaden our ideas about the sphere of architecture so that other ways of building and appropriating habitable space can be disclosed. The adoption of this category was the means best suited to approach this malleable world which is changeable and does not always allow a survey of the daily life of the riverside to be carried out with tangible and fixed items. The study concludes with the design of a map that seeks to add a further support to what is provided by the narrative of the dissertation. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho versa sobre experiências de habitar ribeirinho coletadas no Baixo São Francisco, região atualmente muito fragilizada pelas mudanças no comportamento do rio ocorridas nas últimas décadas. Buscou-se as histórias do cotidiano através da fala desses habitantes, em sua maioria pescadores e mestres de embarcações, mas também observá-los na sua vivência. No que tange aos espaços edificados, uma atenção especial foi dada aos estaleiros, autoconstruções nas margens do rio, que servem de apoio para as atividades ali desenvolvidas. O procedimento da deriva, bem como a produção de diário de bordo e objetos conceituais, se apresentaram como as ferramentas metodológias passíveis de captar e traduzir a atmosfera do lugar, auxiliando na sintonização com um universo tão distinto do acadêmico, ao passo em que também influenciaram a forma como a dissertação foi construída. Assim, uma narrativa sobre o ambiente ribeirinho foi guiada pelo embate da história oral com o olhar e interpretação da pesquisadora, desenvolvida a partir de elementos recortados da paisagem cotidiana dos trabalhadores do rio, e posteriormente explorada através de reflexões cartográficas. Elas foram marcadas por uma desconstrução do mapa tradicional, na qual os conceitos de rizoma, espaço liso e estriado foram chave. Em tempos em que a discussão do patrimônio imaterial ganha relevo, a vivência com os ribeirinhos permitiu ampliar noções concernentes ao âmbito da arquitetura, descortinando outras formas de construir e apropriar o “espaço habitado”. Esta categoria foi a que melhor se adequou para abordar esse universo maleável, mutável e nem sempre aferido com marcos tangíveis e fixos, que é o do cotidiano ribeirinho. O trabalho se conclui com a construção de um mapa que busca deslizar para um outro suporte o que a narrativa da dissertação apresentou.

Made available in DSpace on 2016-06-02T19:29:01Z (GMT). No. of bitstreams: 1 TeseAVL.pdf: 6179060 bytes, checksum: b7f56a22cd08f2d2612296a7e649d302 (MD5) Previous issue date: 2007-02-28 / Universidade Federal de Sao Carlos / The general aim of this study was to establish floristc and phytosociological characteristics of three riverine areas and to analyze the relationship between the distance from the edge of the water and the distribution of the bushlike and arboreous species in the hydrographic basin of the river Taperoá, in the semi-arid region of the state of Paraíba. The research was developed from january/2004 to june/2006 and comprehended riverine areas of the intermittent streams of Cazuzinha (7026 13 S and 36054 30 W; altitude 564-579 m), Mares (7031 53 S and 36033 39 W; altitude 536-550 m) and Farias (7025 33 S and 36029 21 W; altitude 454-470 m). The work of research has taken the following steps: 1) floristic survey of the bushlike and arboreous stratum and analysis of similarities between the sample observed in the area and other studies also developed in the basin of the river Taperoá; 2) characterization of phytosociological structure and 3) analysis of the relationship between the distance of the specimens from the three water courses and their floristc and phytosociological variations. In the first stage, nonsystematic collection of samples of the vegetation has been done monthly. For the second and third stages, 51 contiguous parcels of 10 X 20 m (1.02 ha) have been established for each area, distributed in three parallel strips of land along each course of water. Were measured standing specimens, alive or dead, whose trunk measured &#8805; 3 cm of diameter at ground level (DNS) and whose total height was &#8805; 1 m. In the floristic survey of the three areas, a total of 91 species was registered, of which 68 occurred in the area of the stream Cazuzinha, 62 in the stream Mares and 56 in the stream Farias. The families present in higher number of species and genuses were Euphorbiaceae, Fabaceae, Mimosaceae, Caesalpiniaceae and Rubiaceae. Of the total of species registered for the three areas, 16 are present in the known lists of riverine bushes in other states of Brazil, 26 are endemic of the Caatinga (Brazilian northeastern savanna) and 13 of them had been exclusive of the researched area. The floristic analysis of similarities between the studied areas and the results of five other surveys indicates that floristic similarity between areas is related the geographic distance and characteristics of human occupation and use of the land. For this phytosociological survey, a total of 5,840 specimens have been observed, 5,126 of them alive specimens and 714 dead but still standing. 2,138 of the total observed specimens in the riverine vegetation of the stream Cazuzinha (2,096 individuals.ha-1), 1,838 in the stream Farias (1,802 individuals.ha-1) and 1,864 in the stream Mares (1,827 individuals.ha-1). The total basal area of riverine vegetation of the streams of the Cazuzinha, Farias and Mares were 25.4 m2.ha-1, 15.6 m2.ha-1 and 14.5 m2.ha-1, respectively. Considering each stream particularly, the three more important species in VI were: Aspidosperma pyrifolium, Combretum pisonioides and Caesalpinia pyramidalis (Cazuzinha) and Caesalpinia pyramidalis, Combretum leprosum and Croton sonderianus (Farias and Mares). The average height and diameter of the measured individuals were respectively: 5.4 m and 12.4 cm (Cazuzinha), 3.9 m and 10.5 cm (Farias) and 4.8 m and 10.1 cm (Mares). The values of diversity and equability have been respectively: 2.61 nats.ind.-1 and 0.66 (Cazuzinha), 2.18 nats.ind.-1 and 0.59 (Farias) and 2.77 nats.ind.-1 and 0.72 (Mares). The analysis of the relationship between the distance of the edge of three streams and floristic and phytosociological variations showed that the factor distance is determining for floristic wealth, once, in three environments, the first strip (Closest to stream) is responsible for the highest values in the species quantity. Some of these have occurred exclusively or preferentialy in one or two of the strips while other occurred in the three of them. Among the 10 higher Values of Importance (VI), it was observed that only Caesalpinia pyramidalis, Combretum leprosum and the dead category were present, in different hierarchical positions of VI, in all the strips of the three studied areas. Generally, the first strip (Closest to stream) distinguished itself of the other two (Halfway and Furthest from stream) for the highest total density and total basal area. In the case Cazuzinha and Farias, the values of diversity decreased from Closest to stream towards Furthest from stream; the inverse, however, occurred in the stream Mares where the values diminished from Furthest from stream to Closest to stream. The observed data of average height and diameter, with some exceptions, showed that Furthest from stream presented lesser values when compared to Closest to stream and Halfway. Therefore, we can conclude that the distance from courses of water, possibly depending on water contained in the ground, is one of the main factors that define distribution of the species in space. However, this study indicates the importance of more research in areas of Caatinga, aiming to confirm if the tendential preferences of the species, observed in the present study, are repeated in other conditions. / O objetivo geral deste trabalho foi realizar a caracterização florística e fitossociológica de três áreas ribeirinhas e analisar a relação entre a distância da margem dos cursos d água intermitentes e a distribuição das espécies arbustiva-arbóreas na bacia do rio Taperoá, semi-árido paraibano. A pesquisa foi realizada no período de janeiro/2004 a junho/2006 e abrangeu as áreas ribeirinhas ao longo dos riachos do Cazuzinha (7026 13 S e 36054 30 W; 564-579 m de altitude), Mares (7031 53 S e 36033 39 W; 536-550 m de altitude) e Farias (7025 33 S e 36029 21 W; 454- 470 m de altitude). Nesse sentido, foram adotadas as seguintes etapas de trabalho: 1) levantamento florístico do estrato arbustivo-arbóreo e análise de similaridade entre as áreas ribeirinhas amostradas e outros estudos desenvolvidos na bacia do rio Taperoá; 2) caracterização da estrutura fitossociológica e 3) análise da relação entre a distância da margem dos três cursos d água e as variações florísticas e fitossociológicas. Na primeira etapa foram realizadas mensalmente coletas assistemáticas da vegetação ribeirinha. Para a segunda e terceira etapa foram estabelecidas para cada área 51 parcelas contíguas de 10 X 20 m (1,02 ha), distribuídas em três faixas paralelas ao longo de cada curso d água. Os critérios de inclusão utilizados foram amostrar os indivíduos arbustivo-arbóreos, vivos e mortos ainda em pé, com diâmetro do caule ao nível do solo (DNS) &#8805; 3 cm e altura total &#8805; 1 m. No levantamento florístico das três áreas registrou-se um total de 91 espécies, das quais 68 ocorreram na área do riacho do Cazuzinha, 62 no riacho dos Mares e 56 no riacho do Farias. As famílias com maior número de espécies e de gêneros foram Euphorbiaceae, Fabaceae, Mimosaceae, Caesalpiniaceae e Rubiaceae. Do total de espécies registrado para as três áreas, 16 estão presentes nas listas relacionadas para matas ciliares de outros estados do Brasil, 26 são endêmicas da Caatinga e 13 foram exclusivas. A análise de similaridade florística entre as áreas estudadas e outros cinco levantamentos indicou que a maior identidade florística está relacionada principalmente com a distância geográfica e às características de uso e ocupação da terra. Particularmente relacionado ao levantamento fitossociológico, foram amostrados 5.126 indivíduos vivos e 714 mortos em pé. Do total de indivíduos registrados (5.840), 2.138 foram levantados na mata ribeirinha do riacho do Cazuzinha (2.096 indivíduos.ha-1), 1.838 no riacho do Farias (1.802 indivíduos.ha-1) e 1.864 no riacho dos Mares (1.827 indivíduos.ha-1). A área basal total da vegetação ribeirinha dos riachos do Cazuzinha, Farias e Mares foram 25,4 m2.ha-1, 15,6 m2.ha-1 e 14,5 m2.ha-1 respectivamente. Considerando particularmente cada riacho, as três espécies mais importantes em VI foram: Aspidosperma pyrifolium, Combretum pisonioides e Caesalpinia pyramidalis (Cazuzinha) e Caesalpinia pyramidalis, Combretum leprosum e Croton sonderianus (Farias e Mares). A altura e o diâmetro médios dos indivíduos amostrados foram respectivamente: 5,4 m e 12,4 cm (Cazuzinha), 3,9 m e 10,5 cm (Farias) e 4,8 m e 10,1 cm (Mares). Os valores de diversidade e equabilidade foram respectivamente: 2,61 nats.ind.-1 e 0,66 (Cazuzinha), 2,18 nats.ind.-1 e 0,59 (Farias) e 2,77 nats.ind.-1 e 0,72 (Mares). A análise da relação entre a distância da margem dos três cursos d água e as variações florísticas e fitossociológicas mostrou que a riqueza florística apresentou diferenças quando relacionada à distância da margem dos riachos estudados, sendo a primeira faixa (Margem), nos três ambientes, responsável pelos maiores valores no número de espécies. Algumas destas tiveram ocorrência exclusiva ou preferencial em uma ou duas das faixas enquanto outras ocorreram nas três. Entre os 10 maiores Valores de Importância (VI), observou-se que apenas Caesalpinia pyramidalis, Combretum leprosum e a categoria Mortos estiveram presentes, com diferentes posições hierárquicas de VI, em todas as faixas das três áreas estudadas. De modo geral, a primeira faixa (Margem) destacou-se das demais (Meio e Borda) pela maior densidade total e área basal total. Particularmente relacionado aos valores de diversidade para Cazuzinha e Farias, estes decresceram da Margem para a Borda, entretanto, o inverso ocorreu no riacho dos Mares onde os valores diminuíram da Borda para a Margem. Em relação aos dados de altura e diâmetro médios observou-se, com algumas exceções, que a Borda apresentou os menores valores quando comparada com a Margem e o Meio. Portanto, considerase que o distanciamento dos cursos d água, possivelmente relacionado com o conteúdo de água no solo, seja um dos principais fatores que definem diferentes formas de distribuição espacial das espécies. Entretanto, observa-se a importância de mais estudos em áreas ribeirinhas de Caatinga, visando confirmar se as tendências de preferências apresentadas pelas espécies deste trabalho são mantidas.

Estudos sobre o estado nutricional da população de Rondônia são escassos, principalmente nas localidades ribeirinhas mais isoladas. Estas populações estão expostas a vários fatores ambientais que podem interferir no seu estado nutricional. Portanto, o objetivo principal deste estudo foi avaliar o estado nutricional relativo ao selênio de crianças ribeirinhas de 3 a 9 anos de idade residentes nas localidades de Demarcação, no Rio Machado e Gleba do Rio Preto, no Rio Preto. O método utilizado para avaliação do selênio foi a espectrometria de absorção atômica por geração de hidretos acoplada à cela de quartzo (HGQTAAS). Das 42 crianças estudadas, 74% pertenciam à localidade Demarcação e 26% à Gleba do Rio Preto. De acordo com os pontos de cortes estabelecidos para antropometria, a maioria das crianças das duas localidades apresentou eutrofia. Em relação aos níveis de selênio no plasma, 84% das crianças de Demarcação apresentaram concentrações abaixo do valor de referência, e 16% apresentaram concentrações normais. Por outro lado, as crianças da Gleba do Rio Preto apresentaram concentrações elevadas e acima dos valores de referência estabelecidos. Nos eritrócitos. 45% das crianças residentes na Demarcação apresentaram concentrações baixas do mineral e as demais, níveis normais. Na Gleba, 45% apresentaram concentrações normais e as demais, concentrações acima dos valores de referência. O consumo médio de selênio em Demarcação foi de 41,8&#181;g/dia e na Gleba do Rio Preto, de 179,0&#181;g/dia. Houve correlação significativa apenas entre o consumo de selênio e a concentração deste elemento nos eritrócitos, nas crianças de Demarcação. Desta maneira, conclui-se que as crianças estudadas apresentaram diferenças em relação ao estado nutricional para selênio, as crianças de Demarcação apresentando um estado entre deficiência e normalidade, e as da Gleba do Rio Preto, sujeitas a um possível risco de excesso com possibilidade de efeitos adversos. As concentrações de mercúrio nos cabelos das crianças e em peixes da região foram determinadas por espectrometria de absorção atômica com geração de vapor frio (CV AAS), visando estudar a interação deste elemento com o selênio, e os resultados confirmaram esta possível relação. A maioria das crianças de ambas as localidades apresentou níveis elevados deste metal nos cabelos, assim como foram elevadas as concentrações nos peixes da região. As crianças da Gleba do Rio Preto apresentaram níveis superiores às de Demarcação. / Studies about the nutritional status of population from Rondônia State are scarce, mainly at more isolated riverine places. Populations from these communities are exposed to several environmental factors that interfere in the nutritional status. Thus, the aim of this study was to evaluate the selenium nutritional status of riverine children aged between 3-9 years from Demarcação, placed at Madeira River, and from Gleba do Rio Preto, placed at Rio Preto River. The selenium was analyzed by hydride generation (quartz cell) atomic absorption spectrometry (HGQTAAS). From the 42 evaluated children, 74% of them resided at the first community and the others, at the second one. According to the established cut-offs for anthropometry, the most part of the children from both places were eutrophic. In relation to the plasma selenium levels, 84% of the children from Demarcação presented low levels, while the others 16% had normal levels. On the other hand, all children from Gleba do Rio Preto presented high plasma selenium levels, exceeding the established reference values. In the case of the erythrocyte levels, the percentage of normal and low selenium concentrations in those children from Demarcação was 55% and 45%, respectively. At Gleba do Rio Preto there were high selenium erythrocyte levels in 55% of the children. The mean selenium intake from diet was 41.8 &#181;g/day at Demarcação, and 179.0 &#181;g/day at Gleba do Rio Preto. There was a significant correlation only between the selenium ingested by diet and the erythrocyte selenium levels in those children from Demarcação. Taking the results together, it is possible to conc1ude that the studied children presented differences in relation to the selenium nutritional status with those from Demarcação showing a status between deficiency and normality, and those from Gleba do Rio Preto, a possible risk of excess, being liable to adverse effects. The hair and fishes mercury concentrations were determined intending to study the interaction between this metal with selenium, and the obtained results corroborated this possible relation. The great majority of the children from both places showed high hair mercury levels, as well as the fishes of that region. Children from Gleba do Rio Preto presented higher levels than those from Demarcação.