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91.
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
92.
Alain Houle Colin A. Chapman William L. Vickery 《Behavioral ecology and sociobiology》2010,64(3):429-441
Recently, we demonstrated that the highest densities of fruit pulp are located in the uppermost zones of tree crowns. Since
heterogeneous distributions of depletable food is theorized to foster contest competition, we tested three hypotheses involving
rank differences among species of arboreal frugivores: (1) In the absence of competitors, species tend to feed in higher strata
of tree crowns; (2) interspecific contest competition occurs through monopolization and usurpation of feeding sites in these
higher strata; and (3) subordinate species decrease their feeding height and ingestion rate when dominants enter the food
patch. To test these hypotheses, we observed chimpanzees (Pan troglodytes), red-tailed monkeys (Cercopithecus ascanius), blue monkeys (Cercopithecus mitis), and gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda. We found that: (1) all four primates fed preferentially in upper tree crowns when alone,
(2) dominant species monopolized and aggressively usurped the upper crown when co-feeding with subordinates and the latter
retreated below the middle of tree crowns, (3) in the presence of dominant species, subordinate species showed lower standardized
feeding height and modified their food intake rates, while dominants were not affected by the subordinate species, (4) subordinates
moved down at the arrival of and up at the departure of dominants, and (5) the presence of folivores in the tree did not affect
the feeding height of a frugivore, even through folivores were socially dominant. Contrary to expectations, we found that
red-tailed monkeys decreased their movements between successive fruits that they ate in the presence of blue monkeys compared
to when they were feeding alone, perhaps to avoid disturbing dominants and attracting aggression or because they ingested
more semi-ripe and green unripe fruits, i.e., more food of lower quality. 相似文献
93.
Yigang Yang Huihuang Chen Mamun Abdullah Al Jean Claude Ndayishimiye Jun R Yang Alain Isabwe Anqi Luo Jun Yang 《环境科学学报(英文版)》2022,34(2):140-151
Urbanization often exerts multiple effects on aquatic and terrestrial organisms, including changes in biodiversity, species composition and ecosystem functions. However, the impacts of urbanization on river phytoplankton in subtropical urbanizing watersheds remain largely unknown. Here, we explored the effects of urbanization on phytoplankton community structure(i.e., biomass, community composition and diversity) and function(i.e., resource use efficiency) in a subtropical river at watershed sca... 相似文献
94.
Bonton A Bouchard C Rouleau A Rodriguez MJ Therrien R 《Journal of contaminant hydrology》2012,128(1-4):1-18
Groundwater contamination by nitrate was investigated in an agricultural area in southern Quebec, Canada, where a municipal well is the local source of drinking water. A network of 38 piezometers was installed within the capture zone of the municipal well to monitor water table levels and nitrate concentrations in the aquifer. Nitrate concentrations were also measured in the municipal well. A Water flow and Nitrate transport Global Model (WNGM) was developed to simulate the impact of agricultural activities on nitrate concentrations in both the aquifer and municipal well. The WNGM first uses the Agriflux model to simulate vertical water and nitrate fluxes below the root zone for each of the seventy agricultural fields located within the capture zone of the municipal well. The WNGM then uses the HydroGeoSphere model to simulate three-dimensional variably-saturated groundwater flow and nitrate transport in the aquifer using water and nitrate fluxes computed with the Agriflux model as the top boundary conditions. The WNGM model was calibrated by reproducing water levels measured from 2005 to 2007 in the network of piezometers and nitrate concentrations measured in the municipal well from 1997 to 2007. The nitrate concentrations measured in the network of piezometers, however, showed greater variability than in the municipal well and could not be reproduced by the calibrated model. After calibration, the model was validated by successfully reproducing the decrease of nitrate concentrations observed in the municipal well in 2006 and 2007. Although it cannot predict nitrate concentrations in individual piezometers, the calibrated and validated WNGM can be used to assess the impact of changes in agricultural practices on global nitrate concentrations in the aquifer and in the municipal well. 相似文献
95.
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
96.
Barillet S Adam-Guillermin C Palluel O Porcher JM Devaux A 《Environmental pollution (Barking, Essex : 1987)》2011,159(2):495-502
Because of its toxicity and its ubiquity within aquatic compartments, uranium (U) represents a significant hazard to aquatic species such as fish. In a previous study, we investigated some biological responses in zebrafish either exposed to depleted or to enriched U (i.e., to different radiological activities). However, results required further experiments to better understand biological responses. Moreover, we failed to clearly demonstrate a significant relationship between biological effects and U radiological activity. We therefore chose to herein examine U bioaccumulation and induced effects in zebrafish according to a chemical dose-response approach. Results showed that U is highly bioconcentrated in fish, according to a time- and concentration-dependent model. Additionally, hepatic antioxidant defenses, red blood cells DNA integrity and brain acetylcholinesterase activity were found to be significantly altered. Generally, the higher the U concentration, the sooner and/or the greater the effect, suggesting a close relationship between accumulation and effect. 相似文献
97.
Alain Copinet Estelle Copinet-Legin Florence Fricoteaux Damien Erre 《Journal of Polymers and the Environment》2011,19(1):172-176
The aim of this work was to estimate the biodegradation of a poly(lactic acid) polymeric material by the actinomycetes Kibdelosporangium aridum using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon
balances. The mineralisation rate at the end of the test was compared to those obtained for two basal media. It was shown
that cumulative mineralisation after 45 days of degradation was greater (70%) in vermiculite with a basal medium containing
gelatin than in vermiculite with a basal medium containing glucose (20%). 相似文献
98.
Delatolla R Tufenkji N Comeau Y Gadbois A Lamarre D Berk D 《Water environment research》2012,84(4):328-338
Attached growth biological treatment systems are a promising solution to ammonia removal in cold-temperature climates. Environmental scanning electron microscopy (ESEM) and confocal laser scanning microscopy in combination with fluorescent in situ hybridization (FISH) was used to investigate the effects of 4 months of exposure to 4 degrees C on nitrifying biofilm and biomass. These molecular and microscopic methods were modified to minimize loss of mass and distortion of in situ perspectives. Environmental scanning electron microscopy revealed that nitrifying biofilm did not exhibit significant changes in volume with exposure to 4 degrees C. Confocal laser scanning microscopy in combination with FISH showed that the number of ammonia-oxidizing bacteria (AOB) cells present in the biofilm was statistically consistent during exposure to 4 degrees C. The RNA content of AOB cells remained sufficient for FISH enumeration. The number of nitrite-oxidizing bacteria cells remained steady during exposure to 4 degrees C; however, the RNA content of the cells appeared to decrease with exposure to 4 degrees C, thereby preventing their enumeration using FISH. 相似文献
99.
Estérine Evrard Alain Devaux Sylvie Bony Jérôme Cachot Grégory Charrier Louis Quiniou Jean Laroche 《Environmental science and pollution research international》2013,20(2):676-689
Physiological and genetic responses of age 0+ Platichthys flesus were investigated in the eutrophicated and moderately contaminated Vilaine estuary, during a 6-month survey. The main objective of this study was to explore the biological responses of fishes during their juvenile period in an estuarine system in order to detect a possible selective pressure induced by the environmental stress. Our results showed a general convergence in physiological responses along the survey: an increase in genotoxicity was associated with an increase in mRNA expression of ATPase and betaine homocysteine methyltransferase. These results could suggest an increase of cellular damage, energetic request, and detoxification rate related to the growing exposure time to stress. Considering the aging of the cohort, the genetic characteristics of the Vilaine flounder cohort came closer to the one observed in a highly stressed system, the Seine estuary, suggesting a potential selective pressure mainly induced by the chemical stress. 相似文献
100.
In the polydomous ant species Cataglyphis iberica, nests belonging to the same colony are completely separated during hibernation. In order to examine whether this separation
induces changes both in the hydrocarbon profile and in recognition ability between adult nestmates, we separated groups of
workers for several months under two different conditions: at hibernation temperature and at room temperature. At room temperature,
recognition remained unchanged but separation led to longer mutual antennations relative to non-separated controls. When half
of a colony was placed under hibernation conditions, antennal interactions also increased in duration and a few aggressive
interactions emerged between separated ants. This aggressiveness never reached the intercolonial level observed in this species.
In both cases, the hydrocarbon profiles showed differences between individuals after separation while remaining homogeneous
within each nest. This chemical modification may induce the longer antennations observed. After separated groups were reunited,
individuals recovered their previous antennation pattern and a convergence in hydrocarbon profiles was again observed. These
concurrent observations suggest that hydrocarbons are transferred between nestmates. In C. iberica, the formation of the colonial odor seems to follow the “Gestalt” model which allows all satellite nests of a colony to have a common colonial odor. In the field, temporary nest isolation
during hibernation may induce divergence between satellites. The role of adult transport in connecting nests during the active
season to obtain an efficient Gestalt odor is discussed.
Received: 16 June 1997 / Accepted after revision: 25 October 1997 相似文献