Short- and Long-Term Vegetative Propagation of Two <Emphasis Type="Italic">Spartina</Emphasis> Species on a Salt Marsh in Southern Brazil

Spartina alterniflora and Spartina densiflora are native salt marsh plants from the Atlantic coast; their habitats in Patos Lagoon estuary (southern Brazil) are characterized by a microtidal regime (<0.5 m) and, during El Niño events, high estuarine water levels and prolonged flooding due to elevated freshwater discharge from a 200,000-km² watershed. During and between El Niño events, the vegetative propagation of these two Spartina species in the largest estuary of southern Brazil (Patos Lagoon) was evaluated by monitoring transplanted plants for 10 years (short-term study) and interpreting aerial photos of natural stands for 56 years (long-term study). During the short-term study, S. alterniflora quickly occupied mud flats (up to 208 cm year^?1) by elongation of rhizomes, whereas S. densiflora showed a modest lateral spread (up to 13 cm year^?1) and generated dense circular-shaped stands. However, moderate and strong El Niño events can promote excessive flooding and positive anomalies in the estuarine water level that reduce the lateral spread and competitive ability of S. densiflora. During the long-term study, natural stands of S. alterniflora and S. densiflora had steady lateral spread rates of 152 and 5.2 cm year^?1, respectively, over mud flats. In the microtidal marshes of the southwest Atlantic, the continuous long-term lateral expansion of both Spartina species embodies periods of intense flooding stress (moderate and strong El Niños), when there is a decrease of vegetative propagation and less stressful low water periods of fast spread over mud flats (non-El Niño periods and weak intensity El Niños).     

Geoelectrical mapping of contamination in the cemeteries: the case study in Piracicaba,São Paulo/Brazil

This paper presents the results of electrical resistivity methods in the area delineation that was potentially contaminated by liquefaction products, which are also called putrefactive liquids in Vila Rezende municipal cemetery, Piracicaba, São Paulo, Brazil. The results indicate a depth of water table between 3.1 and 5.1 m, with two groundwater direction flows, one to the SW and another to the SE. Due to the contamination plumes, which have the same groundwater direction flow, as well the conductive anomalies observed in the geoelectric sections, the contamination suspicions in the area were confirmed. The probable plume to the SE extends beyond the limits of the cemetery. The location of the conductive anomalies and the probable contamination plumes showed that the contamination is linked with the depth of the water table and the burial time. Mapping using the geostatistical method of ordinary kriging applied to the work drew structural characteristics of the regional phenomenon and spatial behavior of the electrical resistivity data, resulting in continued surfaces. Thus, this method has proved to be an important tool for mapping contamination plumes in cemeteries.     

Long-term relationships between climate oscillation and basin-scale hydrological variability during rainy season in eastern Northeast Brazil

ABSTRACT

The high variability in the hydrological regime of the Eastern Hydrological Region (EHR) of Northeast Brazil often results in floods and droughts, leading to serious socio-economic issues. Therefore, this work aimed to investigate connections between spatiotemporal hydrological variability of the EHR and large-scale climate phenomena. Multivariate statistical techniques were applied to relate climate indices with hydrological variables within two representative river basins in the EHR. The results indicated a multi-annual relationship between the state of the sea surface temperature of the Atlantic and Pacific oceans and anomalous hydrological variability in the basins. In addition, the northern Tropical Atlantic conditions were shown to play an important role in modulating the long-term variability of the hydrological response of the basins, whilst only extreme ENSO anomalies seemed to affect the rainy season. This knowledge is an important step towards long-term prediction of hydrological conditions and contributes to the improvement of water resources planning and management in the EHR.     

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Résumé

Les observations tensiométriques et piézométriques au voisinage du ruisseau des Maurets, dans le bassin du Réal Collobrier, fournissent des informations intéressantes sur les mécanismes hydrologiques en cas de crue. Des mesures au pas de temps hebdomadaire montrent une bonne corrélation entre le débit dans la rivière et le niveau piézométrique au voisinage de celle-ci. D'autre part, on observe que ce niveau ne peut monter que si la pression d'eau dans le sol avant la crue est voisines de zéro. D'autres observations tensiométriques plus détaillées ont été effectuées au pas de temps de la demi-heure. Elles montrent que seules les pluies de fortes intensités peuvent provoquer une montée rapide de la pression positive d'eau du sol (saturation), à condition que cette pression soit très voisine de zéro avant la pluie. Dans ce cas, le gradient vertical de la charge hydraulique est quasi-nul, et des zones saturées contributives apparaissent et se développent, accompagnées de forts débits de crue dans la rivière. Ainsi, même dans des conditions méditerranéennes, les crues peuvent être provoquées par le développement des surfaces saturées contributives au voisinage des rivières. Dans ce cas, sur le bassin étudié, ces surfaces saturées ont une durée de vie très courte.     

Out‐of‐plane behaviour of a full scale stone masonry façade. Part 1: specimen and ground motion selection

The out‐of‐plane response of walls in existing stone masonry buildings is one of the major causes of vulnerability commonly observed in post‐earthquake damage surveys. In this context, a shaking table (ST) test campaign was carried out on a full‐scale masonry façade mainly focusing on the characterization of its out‐of‐plane overturning behaviour. The structure tested on the ST is a partial reproduction of an existing building from Azores, damaged during the 9 July 1998 Faial earthquake. The definition of the tested specimen as well as the selection of the input ground motion is reported in this paper. A specific emphasis is given to the definition of the time‐history to be applied during the tests because it was felt as an essential and crucial part of the work to obtain the desired overturning behaviour. The accelerogram to be imposed was selected from a large set of accelerograms (74) by means of a step‐by‐step procedure on the basis of several numerical analyses resorting to the rocking response of rigid blocks. A companion paper (Part 2) focuses on the ST test results and detailed data interpretation. Copyright © 2013 John Wiley & Sons, Ltd.     

Temporal evolution of lead isotope ratios in sediments of the Central Portuguese Margin: A fingerprint of human activities

Stable Pb isotope ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb), ²¹⁰Pb, Pb, Al, Ca, Fe, Mn and Si concentrations were measured in 7 sediment cores from the west coast of the Iberian Peninsula to assess the Pb contamination throughout the last 200 years. Independently of their locations, all cores are characterized by increasing Pb/Al rends not related to grain-size changes. Conversely, decreasing trends of ²⁰⁶Pb/²⁰⁷Pb were found towards the present. This tendency suggest a change in Pb sources reflecting an increased proportion derived from anthropogenic activities. The highest anthropogenic Pb inventories for sediments younger than 1950s were found in the two shallowest cores of Cascais and Lisboa submarine canyons, reflecting the proximity of the Tagus estuary. Lead isotope signatures also help demonstrate that sediments contaminated with Pb are not constrained to estuarine–coastal areas and upper parts of submarine canyons, but are also to transferred to a lesser extent to deeper parts of the Portuguese Margin.     

Floods control the influence of environmental gradients on the diversity of zooplankton communities in a neotropical floodplain

Floodplains show a high biodiversity due to their spatial heterogeneity and temporal variability, which are governed by environmental dynamics resulting from the flood pulse. We evaluated the importance of this driving force, the flood pulse, in the structuring of environmental gradients that influence species diversity in a neotropical floodplain. Gamma (γ) and alpha (α) zooplankton diversities were higher in the year with a typical flood pulse (2010), indicating that flood dynamics contributed to high diversity component values. We found significant relationships between α- and β-diversity and local environmental gradients, indicating that in years with a flood pulse, environmental filters might be the dominant mechanisms that structure the zooplankton community. Additive partitioning of γ-diversity showed that even in 2000 with atypical flood conditions, zooplankton diversities showed non-random patterns of spatial distribution and temporal variation in the floodplain. Our results indicate that the driving force of a floodplain can determine the spatial distribution of α- and β-diversity of aquatic communities owing to its primary effect on environmental filters. Therefore, if human activities that influence this driving force, such as water regulation, affect those environmental filters, floodplain biodiversity may decline.     

Predicting seasonal and hydro-meteorological impact in environmental variables modelling via Kalman filtering

This study focuses on the potential improvement of environmental variables modelling by using linear state-space models, as an improvement of the linear regression model, and by incorporating a constructed hydro-meteorological covariate. The Kalman filter predictors allow to obtain accurate predictions of calibration factors for both seasonal and hydro-meteorological components. This methodology can be used to analyze the water quality behaviour by minimizing the effect of the hydrological conditions. This idea is illustrated based on a rather extended data set relative to the River Ave basin (Portugal) that consists mainly of monthly measurements of dissolved oxygen concentration in a network of water quality monitoring sites. The hydro-meteorological factor is constructed for each monitoring site based on monthly precipitation estimates obtained by means of a rain gauge network associated with stochastic interpolation (kriging). A linear state-space model is fitted for each homogeneous group (obtained by clustering techniques) of water monitoring sites. The adjustment of linear state-space models is performed by using distribution-free estimators developed in a separate section.     

A Chart for Judging Optimal Sample Spacing for Ore Grade Estimation

Mineral deposit grades are usually estimated using data from samples of rock cores extracted from drill holes. Commonly, mineral deposit grade estimates are required for each block to be mined. Every estimated grade has always a corresponding error when compared against real grades of blocks. The error depends on various factors, among which the most important is the number of correlated samples used for estimation. Samples may be collected on a regular sampling grid and, as the spacing between samples decreases, the error of grade estimated from the data generally decreases. Sampling can be expensive. The maximum distance between samples that provides an acceptable error of grade estimate is useful for deciding how many samples are adequate. The error also depends on the geometry of a block, as lower errors would be expected when estimating the grade of large-volume blocks, and on the variability of the data within the region of the blocks. Local variability is measured in this study using the coefficient of variation (CV). We show charts analyzing error in block grade estimates as a function of sampling grid (obtained by geostatistical simulation), for various block dimensions (volumes) and for a given CV interval. These charts show results for two different attributes (Au and Ni) of two different deposits. The results show that similar errors were found for the two deposits, although they share similar features: sampling grid, block volume, CV, and continuity model. Consequently, the error for other attributes with similar features could be obtained from a single chart.