Modeling soil erosion using RUSLE and GIS in a watershed occupied by rural settlement in the Brazilian Cerrado

The installation of a rural settlement complex in the watershed stream Indaiá has promoted changes in land-use and vegetation cover dynamics; however, the effects of intensive agriculture and cattle farming in rural settlements on soil loss rates are not well known. Predictive models implemented in geographic information systems have proven to be effective tools for estimating erosive processes. The erosion predictive model Revised Universal Soil Loss Equation (RUSLE) is a useful tool for analyzing, establishing and managing soil erosion. RUSLE has been widely used to estimate annual averages of soil loss, by both interrill and rill erosion, worldwide. Therefore, the aim of this work was to estimate the soil loss in the watershed stream Indaiá, using the RUSLE model and geoprocessing techniques. To estimate soil loss, the following factors were spatialized: erosivity (R), erodibility (K), topography (LS), land-use and management (C) and conservation practices (P); the annual soil loss values were calculated using the RUSLE model equation. The estimated value of soil loss in the hydrographic basin ranged from 0 to 4082.16 Mg ha^?1 year^?1 and had an average value of 47.81 Mg ha^?1 year^?1. These results have demonstrated that 68.16 % of the study area showed little or no soil loss based on the Food and Agriculture Organization’s (FAO 1980) classification. When comparing the average value of soil loss obtained using the RUSLE model with the Natural Potential for Erosion, a 16-fold reduction in soil was found, which highlighted the fact that vegetation cover (C factor) has a greater influence than other factors (R, K and LS) on soil loss prediction attenuation. These results lead to the conclusion that soil loss occurs by different methods in each settlement in the basin and that erosive processes modeled by geoprocessing have the potential to contribute to an orderly land management process.     

Female ornaments signal own and offspring quality in a sex‐role‐reversed fish with extreme male parental care

Although female ornaments have been described in many taxa, the full spectrum of information conveyed by such traits together with the potential male fitness benefits are far from fully understood. Here, we used a sex‐role‐reversed species, the black‐striped pipefish, Syngnathus abaster, where females are the ornamented sex and intensively compete for mates who present an extreme form of paternal care (male pregnancy). We investigated what information is conveyed by female traits and if males are using it during mate choice. We further assessed which traits would reflect offspring quality at birth. We found that although body length generally portrays information on female reproductive potential (gonadosomatic index and oocyte diameter), it does so indirectly. Different aspects of the female traits, such as stripe width and trunk broadness, were found to be better direct indicators. When size is kept constant, males prefer females with wider stripes. Moreover, stripe coloration was found to reflect offspring quality as darker‐striped females produced larger newborns. Our observations suggest that in a species with exclusive paternal care, independently from the male's direct investment in reproduction, female contribution decisively impacts male fitness. Thus, at least in sex‐role‐reversed species such as the black striped pipefish, female ornaments can be selected in an analogous way to those of males in species with conventional sex roles (i.e. by mate choice).     

CDM implementation in Brazil’s rural and isolated regions: the Amazonian case

There is a growing understanding that energy services play a crucial role in underpinning efforts to achieve the UN Millennium Development Goals (MDG) and in improving the lives of poor people. Brazil remains challenged in regard to a number of social issues, notably poverty reduction in isolated areas, where access to electricity is as poor as their population. In the Amazonian region, most people have no access to electricity, or else have only a precarious supply. Due to several economic and technical reasons, many cities have old, inefficient diesel generators. In such a scenario, CDM (Clean Development Mechanism) can be an instrument both to mitigate climate change and to promote sustainable development in these remote areas, thereby contributing to the achievement of the MDGs in Brazil. However, CDM implementation in Brazil is still restricted to a few types of projects (such as sugar cane bagasse cogeneration and landfill gas use), mostly proposed by big companies and hardly ever directed to the Amazon region. The main objectives of this article are to assess the potential of CDM as a possible tool to promote electricity access to the poor rural population in the Amazonian region, and to discuss the main reasons why it has not become a reality so far.     

Chronologie et évolution des fluides hydrothermaux dans le district à fluorine de Santa Catarina,Brésil: Données de l'analyse des terres rares et de l'étude des inclusions fluides

RésumRé Dans le district de Santa Catarina, la teneur en terres rares des fluorines filoniennes caractérise chacune des neuf générations successives mises en évidence (concentrations en Sm, rapports La/Sm ou La/Yb, anomalie en Europium). Deux cycles hydrothermaux majeurs, rapportés au rifting Sud-Atlantique (130-115 m.a.) ont été distingués à partir de l'évolution des rapports La/Sm et La/Yb et des températures d'homogénisation des inclusions aqueuses primaires. Dans cette évolution, une coupure brutale sépare les générations I–IV et V–VI. Les fluorines plus tardives sont rapportées à un évènement néocrétacé-éotertiaire. Une signature géochimique constante est notée pour les terres lourdes, quelle que soit la génération considérée (ex: Yb/Tb = 5; Gd/Yb = 1) suggérant l'existence d'une source unique pour les terres rares et probablement le fluor. A titre d'hypothèse, on pense qu'il s'agit de fluorine disséminée dans les granitoïdes altérés du socle.

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In the Santa Catarina district, REE contents of vein fluorites characterize each one of the nine successive generations (Sm concentrations, La/Sm or La/Yb ratio, Eu anomaly). Two main hydrothermal cycles, related to the South Atlantic rifting (130-115 m.y.), are distinguished through the evolutions of the La/Sm and La/Yb ratios and of the homogenization temperatures of primary aqueous inclusions. In this evolution, a sharp break separates generations I–IV and V–VI. Later fluorite deposits are related to a Neo-Cretaceous-to-Eo-Tertiary event. A constant geochemical signature for heavy REE is noticed, whatever the fluorite generation (e.g. Yb/ Tb = 5; Gd/Yb = 1) suggesting an unique source for REE and possibly fluorine. This source is tentatively determined as disseminated fluorite in altered granitoids from the basement.

     

Genetic and metamorphic conditions constrained by fluid inclusions from Paleoproterozoic (c. 1.8 Ga) magnesite ore deposits, NE Brazil

Precambrian magnesite occurrences hosted by metadolomites from the Orós belt, Ceará, Brazil, are part of a greenschist–amphibolite, metavolcano-sedimentary terrain, dated at 1.8 Ga, cut by Meso- to Neoproterozoic Brasiliano granites and Neoproterozoic basic sills. These rocks were affected by a shear zone between 580 and 500 Ma. The magnesite-bearing marbles can be grouped as medium-grained (1–9 mm) at the Riacho Fundo ore deposit or sparry magnesite (1–15 cm) at the Cabeça de Negro ore deposit. The sparry magnesite shows textural characteristics related to original sedimentary structures. Both types of magnesite-bearing marbles contain aqueous and aqueous-carbonic fluid inclusions that yield homogenization temperatures between 170 and 370 °C. Applying a pressure correction, these temperatures are compatible with the evolution from greenschist to amphibolite facies metamorphic conditions, as described in previous work on the Orós region. It also agrees with data in specialized literature on the metamorphism of carbonate rocks. Fluid inclusion distribution, composition, and physical-chemical characteristics suggest temperature increase, probably related to metamorphism on these rocks. The medium-grained magnesite records partial contamination of CO₂-rich inclusions by relict carbonaceous material (bitumen, hydrocarbons?) that favors, but does not confirm, a syngenetic sedimentary origin and could have caused the lowering of CO₂ melting point in these inclusions. Therefore, though textural evidence points to a sedimentary-diagenetic model, fluid inclusions record conditions of a metamorphic event.     

UV observations of the symbiotic star EG And

EG And is a S-type symbiotic star. Here is present UV observations made by IUE from 1978 to 1991. From these observations the electronic density and the electronic temperature were obtained. The size of He II emitting region was estimated as 7.3R . Line and continuum variations confirm the binary nature of EG And.     

Aridity indices to assess desertification susceptibility: a methodological approach using gridded climate data and cartographic modeling

Natural Hazards - Desertification is a land degradation phenomenon with dire and irreversible consequences, affecting different regions of the world. Assessment of spatial climate susceptibility to...     

Phytoplankton community in the tropical lake of Lagoa Santa (Brazil): Conditions favoring a persistent bloom of Cylindrospermopsis raciborskii

This study presents data on seasonal changes of the phytoplanktonic community of a small tropical lake, Lagoa Santa, in the Brazilian cerrado. Temporal variation in the community structure was small and we observed a permanent dominance of the cyanobacteria Cylindrospermopsis raciborskii. This dominance could be associated to the stability of several environmental conditions. Especially water temperature, always within the optimal growth range for C. raciborskii, and the constant mixed water column may have been important factors driving to the long term dominance of this species in the lake. Remarkable seasonal variation in rainfall, as well as the occasional and non-seasonal variation in nutrient concentrations, were important to explain changes in environmental and biological variables, but were not related to the dominance of C. raciborskii. Pearson's correlation and PCA could just in part explain the stable dominance of this cyanobacterium. Meteorological and chemical factors seem to have no clear control on the variability of the phytoplankton dynamics in Lagoa Santa. The weak relationship between C. raciborskii abundance and environmental variables points to additional intrinsic factors associated to this species that may be important in structuring the phytoplankton assemblage.