Aboveground Biomass Patterns of Dominant Spartina Species and Their Relationship with Selected Abiotic Variables in Argentinean SW Atlantic Marshes     

Diana I. Montemayor  Alejandro D. Canepuccia  Jesus Pascual  Oscar O. Iribarne 《Estuaries and Coasts》2014,37(2):411-420

Salt marsh zonation patterns generate different abiotic and biotic conditions that can accentuate species inherent differences in primary production and biomass. In South West Atlantic marshes, there are two Spartina species: Spartina alterniflora in the low intertidal and Spartina densiflora in the high intertidal. These two species are generally found in all marshes but with different dominance: In some marshes, the S. densiflora zone occupies higher extents, and in others, the S. alterniflora zone is the one that prevails. We found through field sampling that, in six studied marshes, there is greater S. densiflora live and total (i.e., dead+live) aboveground biomass (g m^?2) in the marshes dominated by S. densiflora than in the ones dominated by S. alterniflora. Spartina alterniflora had similar aboveground biomass in the six marshes, regardless of the dominance of each species. When comparing the two Spartina species within each marsh, S. densiflora had greater live and total biomass in the marshes it dominates. In the marshes dominated by S. alterniflora, both species had similar live and total biomass. In all marshes, there was greater dead S. densiflora biomass. A multivariate analysis using selected abiotic factors (i.e., salinity, latitude, and tidal amplitude) showed that S. alterniflora aboveground biomass patterns are mainly correlated with salinity, while S. densiflora live biomass is mainly correlated with salinity and latitude, dead biomass with salinity and tidal amplitude, and total biomass with salinity alone. We conclude that in S. densiflora dominated marshes, the main processes of that species zone (i.e., nutrient accumulation) will be accentuated because of its higher biomass. We also conclude that climatic conditions, in combination with specific Spartina biotic and ambient abiotic parameters, can affect marsh ecological functions.  相似文献   

Assessing risk to groundwater quality using an integrated risk framework     

Mike W. M. Simpson  Diana M. Allen  Murray M. Journeay 《Environmental Earth Sciences》2014,71(11):4939-4956

Source-water protection strategies are ideally focused where the greatest amount of harm reduction can occur. This process of risk management requires an assessment of the spatial variability of risk to water. The assessment methodology presented herein combines aquifer susceptibility with a hazard threat inventory and an analysis of the consequence of contamination to assess the risk to water quality. Aquifer susceptibility combines the intrinsic susceptibility of the physical system with anthropogenic features that locally increase susceptibility. Hazard threats are assessed based on the properties of the chemicals (toxicity and environmental fate), the potential magnitude (extent and quantity of release) and the likelihood of release. The consequence is herein considered as the financial costs of the loss of the resource, including the replacement of a water source and the economic loss where water intensive businesses are lost. A second scenario is included that analyses health issues related to pathogen sources as well as the financial impact to the community where people fall ill and present a financial burden to the public health care system. The risk assessment methodology is applied to the Township of Langley, in southwestern British Columbia, Canada. The results outline the most vulnerable areas as those where susceptible aquifers coexist with potential chemical and biological threats. The risk is greatest where these vulnerable areas coincide with those with the greatest potential for financial loss: within the capture zones of major municipal production wells and where private wells serve agricultural operations with high annual farm sales.  相似文献   

A fast 2D image reconstruction algorithm from 1D data for the Gaia mission     

Diana L. Harrison 《Experimental Astronomy》2011,31(2-3):157-175

A fast 2-dimensional image reconstruction method is presented, which takes as input 1-dimensional data acquired from scans across a central source in different orientations. The resultant reconstructed images do not show artefacts due to non-uniform coverage in the orientations of the scans across the central source, and are successful in avoiding a high background due to contamination of the flux from the central source across the reconstructed image. Due to the weighting scheme employed this method is also naturally robust to hot pixels. This method was developed specifically with Gaia data in mind, but should be useful in combining data with mismatched resolutions in different directions.  相似文献   

2MASS J01074282+4845188: A new nova-like cataclysmic star with a deep eclipse     

Dinko P. Dimitrov  Diana P. Kjurkchieva 《New Astronomy》2012,17(1):34-37

We present V RI photometry and low-resolution spectroscopy of the object 2MASS J01074282+4845188. The V-shape of the eclipse, the phase variability of the colour indices as well as the presence of a pre-eclipse hump, standstill and flickering allow us to conclude that it is a nova-like cataclysmic star. This is supported by the observed broad emission Hα line. Its single profile with a relatively narrow FWHM but large FWZI is typical for a nova-like variable of SW Sex subtype. The observed deep eclipses make the newly discovered cataclysmic star 2MASS J01074282+4845188 an interesting object for future investigation.  相似文献   

Spatially distributed rainfall thresholds for the initiation of shallow landslides   总被引：3，自引：1，他引：2  

Diana Salciarini  Claudio Tamagnini  Pietro Conversini  Silvia Rapinesi 《Natural Hazards》2012,61(1):229-245

The evaluation of the combined influence of rainfall patterns (in terms of mean intensity and duration) and the geomorphological and mechanical characteristics of hillslopes on their stability conditions is a major goal in the assessment of the shallow landslide triggering processes. Geographic Information Systems (GIS) represent an important tool to develop models that combine hydrological and geomechanical analyses for the evaluation of slope stability, as they allow to combine information concerning rainfall characteristics with topographic and mechanical properties of the slopes over wide areas. In this paper, a GIS-based code is developed to determine physically based intensity/duration rainfall thresholds at the local scale. Given the rainfall duration and the local geometric, hydrological and mechanical characteristics of the slopes, the code evaluates the spatial distribution of the minimum rainfall intensity that triggers shallow landslides and debris flows over a given area. The key feature of the code is the capability of evaluating the time t _p required to reach the peak pore pressure head on the failure surface and computing the corresponding critical intensity/duration thresholds based on post-event peak pore pressures. The reliability of the model is tested using a set of one-dimensional analyses, comparing the physically based thresholds obtained for three different slopes with some empirical rainfall thresholds. In a log–log scale, the thresholds provided by the model decrease linearly with increased rainfall duration and they are bracketed by the empirical thresholds considered. Finally, an example of application to a study area of the Umbria region in central Italy is presented, describing the capability of the model of providing site-specific thresholds for different rainfall scenarios.  相似文献   

Towards sustainable groundwater use: setting long-term goals, backcasting, and managing adaptively   总被引：7，自引：0，他引：7  

Gleeson T  Alley WM  Allen DM  Sophocleous MA  Zhou Y  Taniguchi M  VanderSteen J 《Ground water》2012,50(1):19-26

The sustainability of crucial earth resources, such as groundwater, is a critical issue. We consider groundwater sustainability a value-driven process of intra- and intergenerational equity that balances the environment, society, and economy. Synthesizing hydrogeological science and current sustainability concepts, we emphasize three sustainability approaches: setting multigenerational sustainability goals, backcasting, and managing adaptively. As most aquifer problems are long-term problems, we propose that multigenerational goals (50 to 100 years) for water quantity and quality that acknowledge the connections between groundwater, surface water, and ecosystems be set for many aquifers. The goals should be set by a watershed- or aquifer-based community in an inclusive and participatory manner. Policies for shorter time horizons should be developed by backcasting, and measures implemented through adaptive management to achieve the long-term goals. Two case histories illustrate the importance and complexity of a multigenerational perspective and adaptive management. These approaches could transform aquifer depletion and contamination to more sustainable groundwater use, providing groundwater for current and future generations while protecting ecological integrity and resilience.  相似文献   

Spatial distribution of canine faeces in Buenos Aires suburbs: implications for public health     

Mayra Milkovic  Aníbal E Carbajo  Diana Rubel 《Area》2009,41(3):310-318

Canine faecal contamination contributes to environmental degradation and increases the exposure of humans – mainly children – to helminth infections. We studied the magnitude and spatial distribution of faecal contamination on the pavements of two neighbourhoods representative of Buenos Aires suburbs. The pavements of a low-income neighbourhood (LIN) and a middle-income neighbourhood (MIN) were selected at random. Field maps including all substrates and objects observed on each pavement were drawn, viewed from above, on millimetre paper at 1:100 scale. Data were then loaded into a geographic information system (GIS) Arc View 3.1 with a digitiser board. The spatial distribution of faeces and its association with substrates or standing elements were analysed at three scales: substrate, pavement and neighbourhood.
Permeable substrate cover was higher in LIN (75%) than in MIN (35%). The faeces were not homogeneously distributed on the substrates. In both neighbourhoods, the substrates with >50 per cent grass cover showed a significantly higher proportion of faeces than those with <50 per cent grass cover, bare soil and tile. At pavement scale, the number of faeces on pavements was not related to either the number of trees, posts and domiciled dogs in the block, or with the number of faeces and percentage cover of each substrate. At patch scale, substrate patches with faeces were larger than those without faeces. Patches with faeces did not differ in shape between neighbourhoods and were more regularly shaped than patches without faeces.
The spatial distribution of faeces relative to each other was almost random, even when analysed in relation to trees or standing objects. Strategies for the sustainable control of this problem are suggested.  相似文献   

Variations of phytoplankton productivity and biomass over an annual cycle in Saanich Inlet,a British Columbia fjord     

Damian S. Grundle  David A. Timothy  Diana E. Varela 《Continental Shelf Research》2009

Saanich Inlet is a highly productive temperate fjord with the capability to record inter-annual patterns of water-column primary production in undisturbed laminated sediments. We investigated spatial and temporal variations in primary productivity, total and size-fractionated phytoplankton chl a, dissolved nutrients, temperature and salinity at the head and mouth of Saanich Inlet from May 2005 to November 2006. New primary productivity was also measured from May to October 2006. During the growing season (spring, summer and fall), primary productivity was 1.5 times higher at the mouth than at the head of Saanich Inlet and, averaged across stations, total productivity was 460 g C m⁻² y⁻¹. Average new productivity was 53% and 58% of total primary productivity at the head and mouth of the inlet, respectively, and during the growing season micro-phytoplankton (>20 μm; mainly diatoms) was the most abundant size-class of phytoplankton. These rates of primary production are as high as or higher than those measured in other fjords, possibly because of a tidally-driven fortnightly gravity exchange that supplies nutrients to surface waters that enhance biological production when nutrients would otherwise be limiting. This exchange delivers nutrients at least as far inland as the head station, while nutrients associated with an eddy near the mouth may be the cause of even higher productivity there. We discuss the impact of these nutrient sources to Saanich Inlet on the records of paleoproduction generated from two Ocean Drilling Program cores extracted from this fjord, and suggest that the fortnightly exchange buffers variations in nutrient supply occurring on sub-decadal or decadal scales.  相似文献   

Geochemical study of submicron particulate matter(PM1)in a metropolitan area     

Ismael L.Schneider  Elba C.Teixeira  Guilherme L.Dotto  Diana Pinto  Cheng-Xue Yang  Luis F.O.Silva 《地学前缘(英文版)》2022,(1):417-429

Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization.In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization(PMF)in receptor modeling in the Metropolitan Area of Porto Alegre,Brazil.The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites.Major ion and trace element concentrations were assessed.The average concentrations were 12.8 and 15.2μg/m³ for Canoas and Sapucaia do Sul sites,respectively.Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate.Trace elements,especially Cu,Pb,Zn,Cd,and Ni also made important contributions which are directly associated with anthropogenic contributions.Our results show significantly higher levels in winter than in summer.Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources,especially road traffic,combustion processes and industrial activities,which are grouped in 7 major contributing sources.A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations.This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions,combined with awareness-raising actions for citizens concerning the impact of indoor sources.  相似文献   

Modeling the Crust and Upper Mantle in Northern Beata Ridge (CARIBE NORTE Project)   总被引：1，自引：0，他引：1  

Diana Núñez  Diego Córdoba  Mario Octavio Cotilla  Antonio Pazos 《Pure and Applied Geophysics》2016,173(5):1639-1661

  相似文献