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161.
To determine whether stable isotope measurements of body feathers can be used to investigate the isotopic niche of moulting
(inter-nesting) adult seabirds, we examined the stable carbon (δ13C) and nitrogen (δ15N) isotopic composition of body feathers of breeding wandering albatrosses (Diomedea exulans) from Crozet Islands, southern Indian Ocean. First we showed that the isotopic composition of body feathers was not significantly
different from that of wing feathers, being thus a safe alternative to flight feathers whose collection impairs the birds’
flying ability. Second, we looked at the variances in δ13C and δ15N values resulting from the isotopic measurement of a single feather, four different feathers, and a pool of four feathers
per bird, to delineate the best isotopic analytical procedure. A two-step protocol is proposed that allows investigating both
the intra- and inter-individual components of the niche width of the species. In a first step, isotopic measurements on a
single feather per bird are used to define isotopic specialist from isotopic generalist populations. In a second step and
for generalist populations only, measurements on additional (three) feathers per bird are used to delineate type A from type
B isotopic generalists (Bearhop et al. in J Anim Ecol 73:1007–1012, 2004). Third, from a biological point of view, our data
showed different moulting isotopic niches for adult males and females, and also within female wandering albatrosses. Since
the isotopic composition of body feathers in this species reflects that of wing feathers, our results suggest that, after
validation, body feathers have the potential for investigating the foraging ecology of other Procellariiforms and seabirds
during the poorly known inter-nesting period. 相似文献
162.
Bernard Pelletier Pierre Dutilleul Guillaume Larocque James W. Fyles 《Environmental and Ecological Statistics》2009,16(4):439-466
In two articles, we present ‘coregionalization analysis with a drift’ (CRAD), a method to assess the multi-scale variability
of and relationships between ecological variables from a multivariate spatial data set. In phase I of CRAD (the first article),
a deterministic drift component representing the large-scale pattern and a random component modeled as a second-order stationary
process are estimated for each variable separately. In phase II (this article), a linear model of coregionalization (LMC)
is fitted by estimated generalized least squares to the direct and cross experimental variograms of residuals (i.e., after
the removal of estimated drifts). Structural correlations and coefficients of determination at smaller scales are then computed
from the estimated coregionalization matrices, while the estimated drifts are used to calculate pseudo coefficients at large
scale. The performance of five procedures in estimating correlations and coefficients of determination was compared using
a Monte Carlo study. In four CRAD procedures, drift estimation was based on local polynomials of order 0, 1, 2 (L0, L1, L2) or a global polynomial with forward selection of the basis functions; the fifth procedure was coregionalization analysis
(CRA), in which large-scale patterns were modeled as a supplemental component in the LMC. In bivariate and multivariate analyses,
the uncertainty in the estimation of correlations and coefficients of determination could be related to the interference between
spatial components within a bounded sampling domain. In the bivariate case, most procedures provided acceptable estimates
of correlations. In regionalized redundancy analysis, uncertainty was highest for CRA, while L1 provided the best results overall. In a forest ecology example, the identification of scale-specific correlations between
plant species diversity and soil and topographical variables illustrated the potential of CRAD to provide unique insight into
the functioning of complex ecosystems. 相似文献
163.
164.
Rates of trichloroethene (TCE) mass transformed by naturally occurring biodegradation processes in a fractured rock aquifer underlying a former Naval Air Warfare Center (NAWC) site in West Trenton, New Jersey, were estimated. The methodology included (1) dividing the site into eight elements of equal size and vertically integrating observed concentrations of two daughter products of TCE biodegradation—cis‐dichloroethene (cis‐DCE) and chloride—using water chemistry data from a network of 88 observation wells; (2) summing the molar mass of cis‐DCE, the first biodegradation product of TCE, to provide a probable underestimate of reductive biodegradation of TCE, (3) summing the molar mass of chloride, the final product of chlorinated ethene degradation, to provide a probable overestimate of overall biodegradation. Finally, lower and higher estimates of aquifer porosities and groundwater residence times were used to estimate a range of overall transformation rates. The highest TCE transformation rates estimated using this procedure for the combined overburden and bedrock aquifers was 945 kg/yr, and the lowest was 37 kg/yr. However, hydrologic considerations suggest that approximately 100 to 500 kg/yr is the probable range for overall TCE transformation rates in this system. Estimated rates of TCE transformation were much higher in shallow overburden sediments (approximately 100 to 500 kg/yr) than in the deeper bedrock aquifer (approximately 20 to 0.15 kg/yr), which reflects the higher porosity and higher contaminant mass present in the overburden. By way of comparison, pump‐and‐treat operations at the NAWC site are estimated to have removed between 1,073 and 1,565 kg/yr of TCE between 1996 and 2009. © 2012 Wiley Periodicals, Inc.* 相似文献
165.
Raia-Silvia Massad Andrée Tuzet Benjamin Loubet Alain Perrier Pierre Cellier 《Ecological modelling》2010,221(3):479-494
Agricultural crops can be either a source or a sink of ammonia (NH3). Most NH3 exchange models developed so far do not account for the plants nitrogen (N) metabolism and use prescribed compensation points. We present here a leaf-scale simplified NH3 stomatal compensation point model related to the plants N and carbon (C) metabolisms, for C3 plants. Five compartments are considered: xylem, cytoplasm, apoplasm, vacuole and sub-stomatal cavity. The main processes accounted for are the transport of ammonium (NH4+), NH3 and nitrate (NO3−) between the different compartments, NH4+ production through photorespiration and NO3− reduction, NH4+ assimilation, chemical and thermodynamic equilibriums in all the compartments, and stomatal transfer of NH3.The simulated compensation point is sensitive to paramaters related to the apoplastic compartment: pH, volume and active transport rate. Determining factors are leaf temperature, stomatal conductance and NH4+ flux to the leaf. Atmospheric NH3 concentration seem to have very little effect on the compensation point in conditions of high N fertilization. Comparison of model outputs to experimental results show that the model underestimates the NH3 compensation point for high N fertilization and that a better parametrisation of sensitive parameters especially active trasport rate of NH4+ may be required. 相似文献
166.
A tidal bore is a natural and fragile phenomenon, which is of great importance for the ecology of an estuary. The bore development
is closely linked with the tidal range and the river mouth shape, and its existence is sensitive to any small change in boundary
conditions. Despite their ecological and cultural value, little is known on the flow field, turbulent mixing and sediment
motion beneath tidal bores. Indeed, some striking features can be highlighted in two-dimensional simulations, such as large
velocity fluctuations and flow recirculation structures. Using Large Eddy Simulation method, the numerical results emphasised
the complicated turbulent structures and their unsteadiness under a tidal bore. 相似文献
167.
Pierre Encontre 《Natural resources forum》1999,23(3):261-270
In spite of the wide diversity in the economic performance of small island developing states (SIDS), the apparent prosperity of several SIDS has entailed a global misrepresentation of the economic situation of these countries. While their vulnerability to natural disasters is not denied, the general risk of economic marginalization that many SIDS face in the context of globalization may not have received sufficient attention. The paper attempts to highlight what matters most in the consideration of the economic vulnerability of SIDS and in the debate to prevent their marginalization. It examines the main types of external shocks to which SIDS are vulnerable, and discusses the economic handicaps that are fundamental causes of this vulnerability. Economic specialization (with the predominance of international trade in services) is then a central notion in the analysis of island vulnerability: a better specialization, which may involve diversification and always implies greater international competitiveness, can reduce the exposure or vulnerability of SIDS to external shocks, and induce greater economic stability in these countries. Hence the importance of developing policies to circumvent the specific handicaps of islands and facilitate the realization of new trading opportunities through an emulative use of globalization forces. 相似文献
168.
Agnew LJ Lyon S Gérard-Marchant P Collins VB Lembo AJ Steenhuis TS Walter MT 《Journal of environmental management》2006,78(1):63-76
Researchers have noted that current water quality protection strategies, like nutrient management plans, lack a sound hydrological underpinning for pollutant transport processes. This is especially true for areas like the northeastern U.S. where copious research has shown that variable source area hydrology largely governs runoff generation. The goal of this study was to develop a scientifically justified method to identify the locations that generate overland flow. Furthermore, this methodology must be computationally simple enough that it can be utilized or incorporated into nutrient management plans and other established water quality tools. We specifically tested the reliability of the 'distance from a stream,'D(s), and the 'topographic index,'lambda, to predict areas with a high propensity for generating overland flow, i.e. hydrologically sensitive areas (HSA). HSAs were defined by their probability of generating runoff, P(sat), based on 30 year simulations using a physically based hydrological model. Using GIS, each location's P(sat) was correlated with D(s) and lambda. We used three Delaware Co., NY watersheds in the New York City watershed system with areas varying in size from 1.6 to 37 km2 and with forested and agricultural land uses. The topographic index gave stronger, more regionally consistent correlations with P(sat) than did D(s). Equations correlating lambda and P(sat) for each month are presented and can be used to estimate hydrological sensitivity in the region surrounding our study watersheds, i.e. in Delaware Co. This work is currently being incorporated into an Internet Mapping System to facilitate user-friendly, on-line identification of HSAs. 相似文献
169.
Climate change threats to environment in the tropical Andes: glaciers and water resources 总被引:1,自引:0,他引:1
Pierre Chevallier Bernard Pouyaud Wilson Suarez Thomas Condom 《Regional Environmental Change》2011,11(1):179-187
Almost all of the world’s glaciers in the tropical latitudes are located in the Central Andes (Peru, Bolivia, Ecuador and Colombia). Due to their high altitude, to the high level of radiation and to the tropical climate dynamics, they all are particularly threatened by climate change, as a result of not only warming, but also of changing variability of precipitation. Many glaciers are of crucial importance for the livelihood of the local populations and even for three capitals, Lima (Peru), La Paz (Bolivia) and Quito (Ecuador), which depend on them for water and energy supplies. This paper shows that after a period of increased flow due to the glacier melt disequilibrium, the available water resource will decrease along with the rapid shrinking of the glaciers considered as water reservoirs. The case of the Cordillera Blanca (Peru) is analyzed more in detail with the mid-term (20 years) and long-term (1–2 centuries) impact of the glacier shrinking on the local water resources. Associated risks for the population and consequences for the human activities (tourism, hydropower, agriculture and stock-breeding, large-scale irrigation) are described at each stage of the mountain range. 相似文献
170.
Rousseau AN Lafrance P Lavigne MP Savary S Konan B Quilbé R Jiapizian P Amrani M 《Journal of environmental quality》2012,41(1):52-63
This paper proposes a hydrological modeling framework to define achievable performance standards (APSs) for pesticides that could be attained after implementation of recommended management actions, agricultural practices, and available technologies (i.e., beneficial management practices [BMPs]). An integrated hydrological modeling system, Gestion Intégrée des Bassins versants à l'aide d'un Système Informatisé, was used to quantify APSs for six Canadian watersheds for eight pesticides: atrazine, carbofuran, dicamba, glyphosate, MCPB, MCPA, metolachlor, and 2,4-D. Outputs from simulation runs to predict pesticide concentration under current conditions and in response to implementation of two types of beneficial management practices (reduced pesticide application rate and 1- to 10-m-wide edge-of-field and/or riparian buffer strips, implemented singly or in combination) showed that APS values for scenarios with BMPs were less than those for current conditions. Moreover, APS values at the outlet of watersheds were usually less than ecological thresholds of good condition, when available. Upstream river reaches were at greater risk of having concentrations above a given ecological thresholds because of limited stream flows and overland loads of pesticides. Our integrated approach of "hydrological modeling-APS estimation-ecotoxicological significance" provides the most effective interpretation possible, for management and education purposes, of the potential biological impact of predicted pesticide concentrations in rivers. 相似文献