Littérature scientifique sur le sujet « Ecologic variability »
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Articles de revues sur le sujet "Ecologic variability"
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Baráková, Ivana, Markéta Derdáková, Giovanna Carpi, Fausta Rosso, Margherita Collini, Valentina Tagliapietra, Claudio Ramponi, Heidi C. Hauffe et Annapaola Rizzoli. « Genetic and Ecologic Variability amongAnaplasma phagocytophilumStrains, Northern Italy ». Emerging Infectious Diseases 20, no 6 (juin 2014) : 1082–84. http://dx.doi.org/10.3201/eid2006.131023.
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Movellan, A., R. Schiebel, M. V. Zubkov, A. Smyth et H. Howa. « Quantification of protein biomass of individual foraminifers using nano-spectrophotometry ». Biogeosciences Discussions 9, no 6 (7 juin 2012) : 6651–81. http://dx.doi.org/10.5194/bgd-9-6651-2012.
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Abstract. The ecological role of foraminifers has been largely unknown partly owing to difficulties in determining their individual biomass, although foraminifers are abundant in surface marine sediments. The present study provides a reliable and inexpensive method for the quantification of the protein content of hard-shelled foraminifers as a measure of biomass while preserving the tests for later analyses (e.g., morphometry, stable isotopes) using nano-spectrophotometry. The protein biomass, size, and shell weight of Ammonia tepida are significantly correlated (n = 102, p < 0.001, R2 = 0.5739, and n = 181, p < 0.001, R2 = 0.8288, respectively). Variability in relation between test size and weight, and cell biomass may result from natural variability in horizontal and vertical microenvironments encompassing metabolic state, as well as variability in test morphometry and calcite mass (i.e., test weight). In turn, knowing the size- and species-specific biomass of foraminifers adds valuable information on the trophic and ecologic conditions of modern and ancient marine environments, in particular on the reconstruction of the regional paleoproductivity and flux of organic matter.
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Movellan, A., R. Schiebel, M. V. Zubkov, A. Smyth et H. Howa. « Protein biomass quantification of unbroken individual foraminifers using nano-spectrophotometry ». Biogeosciences 9, no 9 (12 septembre 2012) : 3613–23. http://dx.doi.org/10.5194/bg-9-3613-2012.
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Abstract. The ecological role of foraminifers has been largely unknown partly owing to difficulties in determining their individual biomass, although foraminifers are abundant in surface marine sediments. The present study provides a reliable and inexpensive method for the quantification of the protein content of hard-shelled foraminifers as a measure of biomass while preserving the tests for later analyses (e.g. morphometry, stable isotopes), using nano-spectrophotometry. The protein biomass, is significantly correlated with size, and shell weight of Ammonia tepida (n = 102, p < 0.00001, R2 = 0.462, and n = 181, p < 0.00001, R2 = 0.855). Variability in the relation between test size and weight, and cell biomass may result from natural variability in horizontal and vertical microenvironments encompassing metabolic state, as well as variability in test morphometry and calcite mass (i.e. test weight). In turn, knowing the size- and species-specific biomass of foraminifers adds valuable information on the trophic and ecologic conditions of modern and ancient marine environments, in particular on the reconstruction of the regional palaeoproductivity and flux of organic matter.
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Ahern, J., et S. Galea. « Explaining Variability in Population Health : The Role of Underlying Ecologic Vulnerabilities and Capacities ». American Journal of Epidemiology 163, suppl_11 (1 juin 2006) : S27. http://dx.doi.org/10.1093/aje/163.suppl_11.s27-c.
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Mensing, Scott, John Korfmacher, Thomas Minckley et Robert Musselman. « A 15,000 year record of vegetation and climate change from a treeline lake in the Rocky Mountains, Wyoming, USA ». Holocene 22, no 7 (14 décembre 2011) : 739–48. http://dx.doi.org/10.1177/0959683611430339.
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Future climate projections predict warming at high elevations that will impact treeline species, but complex topographic relief in mountains complicates ecologic response, and we have a limited number of long-term studies examining vegetation change related to climate. In this study, pollen and conifer stomata were analyzed from a 2.3 m sediment core extending to 15,330 cal. yr BP recovered from a treeline lake in the Rocky Mountains of Wyoming. Both pollen and stomata record a sequence of vegetation and climate change similar in most respects to other regional studies, with sagebrush steppe and lowered treeline during the Late Pleistocene, rapid upward movement of treeline beginning about 11,500 cal. yr BP, treeline above modern between ~9000 and 6000 cal. yr BP, and then moving downslope ~5000 cal. yr BP, reaching modern limits by ~3000 cal. yr BP. Between 6000 and 5000 cal. yr BP sediments become increasingly organic and sedimentation rates increase. We interpret this as evidence for lower lake levels during an extended dry period with warmer summer temperatures and treeline advance. The complex topography of the Rocky Mountains makes it challenging to identify regional patterns associated with short term climatic variability, but our results contribute to gaining a better understanding of past ecologic responses at high elevation sites.
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Hershberger, Amanda J., Tracie M. Jenkins et Carol Robacker. « Molecular Genetic Variability of Spigelia marilandica and S. gentianoides ». Journal of the American Society for Horticultural Science 140, no 2 (mars 2015) : 120–28. http://dx.doi.org/10.21273/jashs.140.2.120.
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Despite the ecologic and ornamental potential of southeastern U.S. native Spigelia, little is known about the intraspecific or the interpopulation genetic variation. The southeastern U.S. native Spigelia habitat is becoming more and more fragmented as a result of human activity, making it imperative to gain an understanding of natural genetic variation among and within species and populations for the purpose of obtaining variability for plant breeding and preserve the genetic variability in Spigelia. Therefore, the objective of this study was to use amplified fragment length polymorphism analysis to determine interspecific and intraspecific genetic variation and to evaluate gene flow. Thirteen populations of two species of native Spigelia, S. marilandica (SM), S. gentianoides var. gentianoides (SGG), and S. gentianoides var. alabamensis (SGA), were analyzed using four primer pairs that amplified a total of 269 bands. Based on analysis of molecular variance and estimates of Nei’s coefficients of gene diversity (percentage of polymorphic loci, average genetic diversity within populations, average genetic diversity within species, and proportion of species genetic diversity attributed to among population variation), the majority of variation found in Spigelia occurs within populations. Both among-species and among-population variation was low, likely the effect of common ancestry as well as relatively frequent introgression among individuals (and populations) of Spigelia. When all individuals were evaluated using Nei’s unbiased genetic distances and viewed as a unweighted pair group method with arithmetic mean phenogram, three main groups were shown, one with two samples of SGG from one population, one with 13 individuals from both SGG populations used in this study, and one with all of the SM, SGA, and remaining SGG individuals. Further evaluation using STRUCTURE software showed introgression between populations and species, although all allele clusters have not entirely introgressed into all populations. The significance of these results is discussed in relation to breeding in Spigelia.
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Madkour, Aubrey Spriggs, Sandra L. Martin, Carolyn Tucker Halpern et Victor J. Schoenbach. « Area Disadvantage and Intimate Partner Homicide : An Ecological Analysis of North Carolina Counties, 2004–2006 ». Violence and Victims 25, no 3 (juin 2010) : 363–77. http://dx.doi.org/10.1891/0886-6708.25.3.363.
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Using data from the North Carolina Violent Death Reporting System and other sources, we examined ecologic relationships between county (n = 100) disadvantage and intimate partner homicide (IPH), variability by victim gender and county urbanicity, and potential mediators. County disadvantage was related to female-victim homicide only in metropolitan counties (incidence rate ratio [IRR] 1.25); however, disadvantage was associated with male-victim IPH regardless of county urbanicity (IRR 1.17). None of the potential intervening variables examined (shelter availability, intimate partner violence services’ funding) was supported as a mediator. Results suggest disparities across North Carolina counties in IPH according to county disadvantage. Future research should explore other potential mediators (i.e., service accessibility and law enforcement responses), as well as test the robustness of findings using additional years of data.
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Pachut, Joseph F. « Population genetics of four species of Ordovician bryozoans : stereology and jackknifed analysis of variance ». Journal of Paleontology 61, no 5 (septembre 1987) : 927–41. http://dx.doi.org/10.1017/s0022336000029309.
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Collections of four Ordovician bryozoan species from habitats of differing levels of taxonomic diversity were examined in order to assess the effect of environmental conditions on intraspecific and interspecific morphologic patterns. Up to 20 morphometric characteristics were measured for each species from populations in both high-diversity and low-diversity settings. Character means and the levels of character variability differ between populations in different diversity zones. Across species, mean character values differ significantly in 41 percent of the total comparisons, permitting intraspecific and interspecific multivariate discrimination of populations from the two diversity zones.The partitioning of clonal morphologic variability into within-colony (nonheritable) and among-colony (potentially heritable) components reveals that habitat conditions favoring high diversities appear to promote a greater proportion of potentially heritable genetic variation both within- and among-species than do low-diversity settings wherein a larger percentage of variation is ecophenotypic, or nonheritable, plasticity. Although the actual percentages vary from species to species, this pattern is obtained for representatives of four different trepostome bryozoan families and therefore is robust. Variability of this sort, if unrecognized, could lead to taxonomic oversplitting along ecologic gradients. These local, facultative adjustments to environmental conditions may be indicative of processes involved in the reactions of populations to selective pressures.Analyses such as this, coupled with examinations of character covariances, may permit the recognition not only of environmentally-induced morphologic plasticity and the proportions of potentially heritable and nonheritable variability, but also provide evidence for intraspecific changes in the rates and timing of developmental events (i.e., across-population or facultative heterochrony).
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Abdi, Reza, et Mehdi Yasi. « Evaluation of environmental flow requirements using eco-hydrologic–hydraulic methods in perennial rivers ». Water Science and Technology 72, no 3 (4 mai 2015) : 354–63. http://dx.doi.org/10.2166/wst.2015.200.
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The assessment of environmental flows in rivers is of vital importance for preserving riverine ecosystem processes. This paper addresses the evaluation of environmental flow requirements in three reaches along a typical perennial river (the Zab transboundary river, in north-west Iran), using different hydraulic, hydrological and ecological methods. The main objective of this study came from the construction of three dams and inter-basin transfer of water from the Zab River to the Urmia Lake. Eight hydrological methods (i.e. Tennant, Tessman, flow duration curve analysis, range of variability approach, Smakhtin, flow duration curve shifting, desktop reserve and 7Q2&10 (7-day low flow with a 2- and 10-year return period)); two hydraulic methods (slope value and maximum curvature); and two habitat simulation methods (hydraulic–ecologic, and Q Equation based on water quality indices) were used. Ecological needs of the riverine key species (mainly Barbus capito fish), river geometries, natural flow regime and the environmental status of river management were the main indices for determining the minimum flow requirements. The results indicate that the order of 35%, 17% and 18% of the mean annual flow are to be maintained for the upper, middle and downstream river reaches, respectively. The allocated monthly flow rates in the three Dams steering program are not sufficient to preserve the Zab River life.
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Thomas, E., Kartik Venkataraman, Victoria Chraibi et Narayanan Kannan. « Hydrologic Trends in the Upper Nueces River Basin of Texas—Implications for Water Resource Management and Ecological Health ». Hydrology 6, no 1 (8 mars 2019) : 20. http://dx.doi.org/10.3390/hydrology6010020.
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Reliable water sources are central to human and environmental health. In south Texas, USA, the Nueces River Basin (NRB) directly or indirectly plays that important role for many counties. Several NRB stream segments are designated as ecologically significant because they serve crucial hydrologic, ecologic, and biologic functions. The hydrologically significant streams recharge the Edwards Aquifer, an essential water source for the region’s agricultural, industrial, and residential activities. Unfortunately, the semiarid to arid south Texas climate leads to large inter-annual precipitation variability which impacts streamflow, and as a consequence, the aquifer’s recharge. In this study, we used a suite of hydrologic metrics to evaluate the NRB’s hydroclimatic trends and assess their potential impacts on the watershed’s ecologically significant stream segments using precipitation and streamflow data from the National Climatic Data Center (NCDC) and Hydroclimatic Data Network (HCDN) respectively from 1970 to 2014. The results consistently showed statistically significant decreasing streamflow for certain low-flow indicators over various temporal scales, likely due to water rights diversions and minimal land use changes. This research could help decision-makers develop the necessary tools to manage water resources in south Texas, given the NRB’s significance as a source of water for domestic consumption and ecological health.
Thèses sur le sujet "Ecologic variability"
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Billard, Elodie. « Etude des communautés microbiennes fonctionnelles benthiques impliquées dans le cycle du méthane (Lac du Bourget) ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAA017/document.
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Les communautés microbiennes benthiques participent activement au recyclage de la matière organique et de fait au fonctionnement biogéochimique des écosystèmes lacustres. Ces communautés comportent de nombreux phyla mais leur diversité fonctionnelle est encore incomplètement connue. Ce travail vise à appréhender les modifications de structure et d'abondance des gènes fonctionnels en lien avec la distribution spatiale verticale (liée au gradient d'oxydoréduction), la variabilité spatiale horizontale (zone côtière vs pélagique) et la dynamique saisonnière liée au brassage de la colonne d'eau (ré-oxygénation des interfaces benthiques), de même que l'identification de la diversité des méthanotrophes et des méthanogènes.Pour cette étude, des carottes sédimentaires ont été prélevées sur un transect zone côtière – zone pélagique, à différentes dates au cours d'un cycle annuel. Chaque carotte sédimentaire a été analysée dans la verticalité entre l'interface eau-sédiment et 20 cm. Les communautés microbiennes participant au cycle du méthane ont été ciblées par 2 gènes de fonction et étudiées en termes de structure, de diversité et d'abondance; par ailleurs, des marqueurs phylogénétiques ont été utilisés pour caractériser les communautés bactériennes et archéennes totales.Les résultats de l'étude spatiale montrent que, si à l'échelle locale (station d'échantillonnage) une relative homogénéité des communautés microbiennes (totales et fonctionnelles) est observée, des variabilités fortes sont détectées d'une part à l'échelle des transects horizontaux en lien avec des changements de conditions environnementales et d'autre part dans la verticalité des sédiments sous l'effet des conditions d'oxydoréduction. La communauté bactérienne étant la plus affectée dans la verticalité, avec des changements de structure entre toutes les strates étudiées. Dans cette même étude, une analyse comparative de la structure des communautés (totales et fonctionelles) a démontré que l'analyse d'échantillons individuels permettait d'obtenir un plus grand nombre d'OTU que l'analyse des mêmes échantillons regroupés en pools.Les résultats de l'étude de la dynamique temporelle des communautés méthanogènes et méthanotrophes révèlent des changements de structure et abondance, principalement à l'interface eau - sédiment en lien avec la dynamique d'oxygénation du lac. Quant à l'analyse de la diversité, elle montre une dominance des Methanomicrobiales (Methanoregula principalement) pour les méthanogènes, mais les Methanosarcinales (Methanosarcina) et les Methanobacteriales (Methanobacterium) ont également été identifiés. Pour les méthanotrophes, la diversité est dominée par Methylobacter en zone profonde et par Methylococcus en zone côtière, les méthanotrophes de Type II (Methylosinus et Methylocystis) ont aussi été identifiés.L'ensemble de ces travaux souligne l'importance de prendre en compte, à la fois la variabilité spatiale (horizontale et verticale) et la variabilité temporelle, des communautés méthanogènes et méthanotrophes lors de l'étude de ces communautés. Les changements quant à leurs structures et leurs abondances sont des paramètres non négligeables pour comprendre les processus impliqués dans le cycle du méthaneBenthic microbial communities are actively involved in organic matter recycling and fact biogeochemical functioning of lake ecosystems. These communities comprise many phyla but their functional diversity is still incompletely known. This study is focused on the benthic microbial communities involved in the methane cycle in lacsutrine suystems. We aimed understanding the structural and abundance changes of functional genes related to the vertical distribution (redox gradient in sediment), the horizontal variability (coastal vs. pelagic benthic zone) and seasonal dynamics related to mixing of the water column (re-oxygenation of benthic interface). The composition of methanotrophic and methanogenic communities was characterized by sequencing analyses.For this study, sedimentary cores were sampled along a transect from coastal to pelagic zone, at different times during an annual cycle. In addition, each sediment core was analyzed in its verticality from the water-sediment interface to 20 cm depth. Microbial communities involved in the cycle of methane (methanogenesis and methanotrophy) were targeted by 2 functional genes (mcrA and pmoA). Furthermore, phylogenetic markers were used to characterize the total bacterial and archaeal communities. These communities are studied in terms of structure (genotyping), diversity (sequencing) and abundance (qPCR, DNA) of their functional genes.The results of the study showed that, on a spatial scale, a low heterogeneity was detected for a given sampling station in terms of structure of microbial communities (total and functional), however, a high variability was detected both at an horizontal scale along a transect (costal vs. pelagic zone), due to contrasted environmental conditions, and at a vertical scale (upper to deeper layers in the core) under the effect of redox conditions. The bacterial community being the most affected in the verticality, with structural changes among all strata studied. In the same study, a comparative analysis of the structure (for all of the communities), between pooled samples and individual samples, demonstrated that the analysis of individual samples provided a greater number of OTU for the majority of microbial communities.Moreover the study of the temporal dynamic of methanogen and methanotroph communities revealed changes in the structure and abundance, mainly at the water - sediment interface, according to the oxygenation levels that varied through time. The analysis of diversity showed a dominance of Methanomicrobiales (Methanoregula mainly) for methanogens, but Methanosarcinales (Methanosarcina) and Methanobacteriales (Methanobacterium) were also identified. The methanotrophs' community was dominated by Methylobacter on deeper stations and by Methylococcus in coastal station. Type II methanotrophs (Methylosinus and Methylocystis) were also identified.This work highlights the importance of taking into account both the spatial variability (horizontal and vertical) and the temporal variability of methanogen and methanotroph communities. Changes on their structures and abundances are significant parameters for understanding the processes involved in the methane cycle
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Afán, Asencio Isabel. « Ecological response of marine predators to environmental heterogeneity and spatio-temporal variability in resource availability ». Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/398990.
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Seabirds have evolved within an open and dynamic environment, the ocean. As meso-top predators, seabirds are greatly influenced by the oceanographic conditions driving marine productivity, and therefore, distribution of their prey. Consequently, seabirds’ behaviour and, ultimately, life-history traits are greatly influenced, by the ever-changing oceanographic conditions. However, oceanographic conditions are currently changing at ever-increasing rates due to global warming and human harvest impacting marine ecosystems. Thus, seabirds have become particularly vulnerable to these changes. Accordingly, in this thesis, we investigated the ecological responses of seabirds, in terms of foraging and breeding performance, to the spatio-temporal variability of environmental conditions imposed by oceans and exacerbated by climate and human stressors. In particular, we (i) identified the climate and human stressors impacting the world’s ocean, (ii) investigated the actual scale at which seabirds interact with their environment, (iii) assessed how seabirds respond to oceanographic variability by changing their foraging and reproductive strategies and (iv) proposed an integrative tool for the design of marine reserves protecting seabirds and their environment.
The objectives of this thesis were accomplished through advanced procedures in the fields of satellite remote sensing and animal tracking. Our results confirmed the unprecedented changes experienced by oceans in the last decades. However, we were able to provide deepest insights on the uneven distribution of climate and human driven environmental changes. When investigating the link between such environmental variability and seabirds’ behaviour, we found that dynamic processes as ocean currents were key factors determining the scale at which seabirds interact with their environment. Environmental features driving the spatiotemporal distribution of prey (e.g. sea surface temperature, chlorophyll-a, sea fronts and persistent areas of productivity) along with industrial fisheries played a fundamental role in determining the foraging distribution of seabirds. However, seabirds’ foraging strategies were largely constrained by limitations imposed by their central-place foraging behaviour and by dynamic factors such as prevalent winds, which influenced individual decision-
making in heading directions when foraging. Intra and interspecific competition for resources also modulated foraging distributions, avoiding conspecifics or segregating foraging areas among sympatric species in appropriate stages. In general, we have provided a complete picture of environmental processes affecting seabirds. We argue that this information would be extremely useful for designing suitable management and conservation strategies. Thus, we finally proposed an adaptive framework for delimitation of more meaningful marine reserves that maximises conservation targets for seabirds, while accounting for human activities, environmental and biological factors largely driven seabird performance and, remarkably, the dynamism inherent to marine systems.
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Alegre, Norza Sior Ana Renza Paola. « Trophic ecology of jumbo squid and predatory fishes in the Northern Humboldt Current System ». Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS223/document.
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Ce travail est une contribution à l'étude de l'écologie trophique d'importants prédateurs de la partie Nord du système du Courant de Humboldt (NSCH), le chinchard (Trachurus murphyi), le maquereau (Scomber japonicus) et le calmar géant (Dosidicus gigas). Nous avons caractérisé la variabilité des modes d'alimentation de ces espèces à différentes échelles spatiotemporelles et fourni de nouvelles connaissances sur le comportement alimentaire de ces espèces, définies comme opportunistes par des travaux antérieurs. Pour ce faire, nous avons appliqué une variété de méthodes statistiques à un vaste jeu de données comprenant 27188 estomacs non vides. Sur cette base nous avons décrit l'organisation spatiale de la faune fourrage de ces prédateurs et documenté les changements dans la composition des proies en fonction de la taille de prédateurs et des conditions environnementales. Nos résultats indiquent que l'oxygène dissous jour un rôle clef dans ces processus. Nous avons également résolu un paradoxe sur l'alimentation du calmar géant: pourquoi ils ne se nourrissent guère sur l'immense biomasse d'anchois (Engraulis ringens) présente le long de la côte du Pérou? Nous avons montré que la présence d'une zone de minimum d'oxygène (ZMO) superficielle devant le Pérou pourrait limiter la cooccurrence entre calmars géant et anchois. Pour synthétiser ces résultats, nous avons proposé un modèle conceptuel de l'écologie trophique du calmar géant tenant compte du cycle ontogénétique, de l'oxygène et de la disponibilité des proies. Par ailleurs, nous avons montré que le chinchard et le maquereau se nourrissent des espèces les plus accessibles comme par exemple la galathée Pleurocondes monodon ou les larves zoea. Ces deux prédateurs présentent un chevauchement trophique mais, contrairement à ce qui avait été décrit dans d'autres études, le chinchard n'est pas aussi vorace que le maquereau. Le régime alimentaire de ces poissons est caractérisé par une forte variabilité spatio-temporelle et le talus continental s'avère être une importante frontière biogéographique. La composition du régime alimentaire des poissons prédateurs étudiés n'est pas nécessairement un indicateur cohérent de l'évolution de la biomasse des proies. Les événements El Niño ont eu un faible effet sur le taux de remplissage des estomacs et sur le régime alimentaire du chinchard et du maquereau. Par ailleurs les changements en diversité des proies à échelle décennale contredisent le classique paradigme de corrélation positive entre diversité et température. Finalement, les patrons globaux décrits dans ce travail, illustrent le comportement alimentaire opportuniste, les stratégies de vie et le haut degré de plasticité de ces espèces. Un tel comportement permet de s'adapter aux changements de l'environnementThis work provides a contribution to a better understanding of the trophic ecology of important predators in the Northern Humboldt Current System, the jack mackerel (Trachurus murphyi), the chub mackerel (Scomber japonicus) and the jumbo squid (Dosidicus gigas) by the characterization of the highly variable feeding patterns of these species at different spatiotemporal scales. We provided new knowledge on the comparative trophic behaviour of these species, defined as opportunistic in previous investigations. For that purpose we applied a variety of statistical methods to an extensive dataset of 27,188 non-empty stomachs. We defined the spatial organization of the forage fauna of these predators and documented changes in prey composition according to predators' size and spatiotemporal features of environment. Our results highligh the key role played by the dissolved oxygen. We also deciphered an important paradox on the jumbo squid diet: why do they hardly forage on the huge anchovy (Engraulis ringens) biomass distributed of coastal Peru? We showed that the shallow oxygen minimum zone present off coastal Peru could hamper the co-occurrence of jumbo squids and anchovies. In addition, we proposed a conceptual model on jumbo squid trophic ecology including the ontogenetic cycle, oxygen and prey availability. Moreover we showed that the trophic behaviour of jack mackerel and chub mackerel is adapted to forage on more accessible species such as for example the squat lobster Pleurocondes monodon and Zoea larvae. Besides, both predators present a trophic overlap. But jack mackerel was not as voracious as chub mackerel, contradictorily to what was observed by others authors. Fish diet presented a high spatiotemporal variability, and the shelf break appeared as a strong biogeographical frontier. Diet composition of our fish predators was not necessarily a consistent indicator of changes in prey biomass. El Niño events had a weak effect on the stomach fullness and diet composition of chub mackerel and jack mackerel. Moreover, decadal changes in diet diversity challenged the classic paradigm of positive correlation between species richness and temperature. Finally, the global patterns that we described in this work, illustrated the opportunistic foraging behaviour, life strategies and the high degree of plasticity of these species. Such behaviour allows adaptation to changes in the environment
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Kosanic, Aleksandra. « Ecological responses to climate variability in west Cornwall ». Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/18120.
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Recent (post-1950s) climate change impacts on society and ecosystems have been recognised globally. However these global impacts are not uniform at regional or local scales. Despite research progress on such scales there are still gaps in the knowledge as to 'what' is happening and 'where'? The goal of this study addresses some of these gaps by analysing climate variability and vegetation response at the furthest south westerly peninsula of the United Kingdom. This research is focused on West Cornwall (South West England) - an area dominated by a strong maritime influence. The first part of this PhD research analysed archive and contemporary instrumental data in order to detect any trends in climate variability. The weather data was retrieved from the Met Office archive for Camborne 1957-2010 and Culdrose 1985-2011 stations; Trengwainton Garden (1940-2010), and from the Royal Cornwall Polytechnic Society, for Falmouth (1880-1952) and Helston (1843-1888). The data showed positive trends in mean annual and maximum temperature with the largest trend magnitude in the 20th and 21st century. Seasonal temperature change varies locally with the highest increase in autumn spring and summer. Precipitation trends were only positive for the 19th century for Helston. Correlation between precipitation data and North Atlantic Oscillation (NAO index) was negative, however the opposite result was detected when the NAO index was correlated with temperatures. Surprisingly, return period analysis showed a decrease in the frequency and intensity of extreme precipitation events post 1975 for Camborne and Trengwainton Garden stations. The second part of this study analysed changes in vegetation distribution in West Cornwall using historical and contemporary vegetation records. Historical vegetation records were used from the Flora of Cornwall collection of herbarium records and contemporary vegetation records which were available online, containing mainly the 'New Atlas of British and Irish flora'. Data sets were geo-referenced using ArcGIS in order to analyse changes in species geographical distribution pre and post-1900. Analysis showed that historical vegetation records can be used to assess any changes in geographic distributions of vegetation. Analysis for the area of West Cornwall showed a loss of range for 18 species, for 6 species this loss was larger than 50% of the area, and there was no change in overall range area for 10 species. Ellenberg values and environmental indicator values showed that they can be used as an indicator of environmental change, showing a decrease in species with lower January temperatures. Analysis also showed an increase in moderate wetter species, where species with extreme low and high precipitation environmental indicator values showed a greater loss. Furthermore species with a higher requirement for light showed a loss as well as species with lower nitrogen values. To analyse the loss of species at the local scale, West Cornwall was divided into three areas (North Border Cells, Central West Cornwall Cells and South Border Cells). The highest loss of 11 species was detected for South Border Cells, where the loss for Central West Cornwall Cells was 6 and for North Border Cells 8 species. It was found that 17 species were experiencing loss on different local sites. For 9 of these 17 species, change at the local scale was different to the national scale change at the individual species level, group level and habitat level. Furthermore, the whole area of West Cornwall lost two species post-1900, with a different loss locally. This showed that species could be protected locally in appropriate microclimate refugia, which will be of benefit for the preservation of regional identity ecosystem services and overall genetic pool of the species.
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Alexandre, Carlos Manuel Engeitado. « Ecological impact of streamflow variability in the bio-ecology of freshwater fishes from permanent and temporary mediterranean river systems ». Doctoral thesis, Universidade de Évora, 2014. http://hdl.handle.net/10174/14671.
Texte intégralRésumé :
Natural streamflow variability is important for riverine ecosystems but river regulation modifies flow patterns,
disturbing fish bio-ecology. This thesis includes a characterization of basal biological differences between
non-regulated permanent and temporary Mediterranean rivers and analyzes the effects of three types of
regulation on fish assemblage composition, movement, diet and life-history. Fish from non-regulated
permanent rivers had higher swimming performance, a higher percentage of invertebrates in their diet,
mature at an older age, later in the year and have higher growth rates. By homogenizing flow pattern,
regulation for water derivation and agriculture affected fluvial specialists, benefiting generalist species,
promoted the consumption of plants and detritus, and decreased fish growth rates, condition and
reproductive activity. Regulation for hydroeletricty induced short-term flow and habitat changes that
increased fish seasonal movement and home range. These findings allow understanding bio-ecological
changes imposed by flow regulation and can be used as guidelines for flow requirements implementations; Resumo:
Impacto de diferentes regimes hidrológicos na bio-ecologia dos peixes dulciaquícolas em
rios Mediterrânicos permanentes e temporários
Esta tese inclui uma caracterização das diferenças biológicas entre rios Mediterrânicos não regularizados de
regime permanente e temporário e analiza os efeitos de três tipos de regularização na composição,
movimento, dieta e ciclos de vida dos agrupamentos piscícolas. Peixes de rios permanentes não
regularizados apresentam uma maior capacidade natatória, um maior consumo de invertebrados,
reproduzem-se mais tarde e possuem maior taxa de crescimento. Através da homogeneização do caudal,
as barragens para derivação e agricultura afetam as espécies especializadas, beneficiando as generalistas,
promovem o consumo de detritos e o decréscimo da taxa de crescimento, condição corporal e actividade
reprodutora. A regularização para fins hidroelétricos induz uma acentuada variação do caudal e habitat, a
uma escala temporal menor, contribuindo para o aumento do movimento e área utilizada pelos peixes.
Estes resultados permitem compreender as alterações bio-ecologicas impostas pela regularização do
caudal e podem ser usados em futuros programas de reabilitação fluvial.
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Joyce, Andrew Noel. « Modelling surface climate over complex terrain for landscape ecology ». Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4245/.
Texte intégralRésumé :
Climate exerts a fundamental control on ecosystem function, species diversity and distribution. Topographic variability may influence surface climate, through processes operating at a landscape- scale. To quantify and model such influences, the topography of a 72 km(^2) area of complex terrain, (including the Moor House National Nature Reserve in northern England) was analysed at 50 m resolution. A suite of topographic variables was created, including distance relative to the Pennine ridge (dist), and elevation difference between each grid cell and the lowest grid cell within a specified neighbourhood {drain). Automatic weather stations (AWS) were deployed in a series of networks to test hypothetical relationships between landscape and climate. Daily maximum air temperature, daily mean soil temperature and daily potential evapotranspiration can be modelled spatially using a daily lapse rate calculated from the difference between daily observations made at two base stations. On days with a south easterly wind direction, daily mean temperature is estimated as a function of lapse rate and dist; the spatial behaviour of temperature is consistent with a föhn mechanism. Daily minimum temperature is modelled using lapse rate and drain on days with a lapse rate of minimum temperature shallower than -2.03 x 10 C m(^-1), incorporating the effects of katabatic air flow. Daily solar radiation surfaces are estimated by a GIS routine that models interactions between slope and solar geometry and accounts for daily variations in cloudiness and daylight duration. The daily climate surfaces were tested using data measured at a range of AWS locations during different times of year. The accuracy of the daily surfaces is not seasonally-dependent. The spatial climate data are particularly well suited to landscape-scale ecology because the methods account for prevailing topoclimatic constraints and because separate climate surfaces are generated for each day, capturing the high frequency variability characteristic of upland regions.
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Avois-Jacquet, Carol. « Variabilité spatiale multiéchelle du zooplancton dans un lagoon récifal côtier (Multiscale spatial variability of zooplankton in a coastal reef lagoon) ». Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00001767.
Texte intégralRésumé :
Variabilité spatiale multiéchelle du zooplancton dans un lagoon récifal côtier - L'identification des changements dans les patrons écologiques selon l'échelle spatiale et la compréhension des processus qui génèrent ces changements sont d'une importance considérable en océanographie. Dans ce contexte, comprendre comment une communauté biologique répond à l'hétérogénéité environnementale requiert la connaissance des processus impliqués et l'échelle spatiale à laquelle ils opèrent. Les relations spatiales entre la variabilité du zooplancton et l'hétérogénéité environnementale sont encore imprécises dans les écosystèmes tropicaux côtiers. L'objectif de ce travail de thèse a donc été de déterminer les échelles de dépendance spatiale des patrons du zooplancton associé à un lagon récifal côtier et des processus environnementaux sous-jacents. Dans ce contexte, les intérêts de cette recherche ont été de quantifier les patrons de la variabilité du zooplancton dans l'espace, de comprendre comment ces patrons changent avec l'échelle spatiale et de déterminer les processus physiques et biologiques responsables de ces patrons spatiaux. L'échantillonnage, effectué le long d'un transect de la côte vers le large dans le lagon du Grand-Cul-de-Sac Marin (Guadeloupe), a concerné deux classes de taille du zooplancton (190–600 µm et > 600 µm) pour lesquelles la biomasse et l'abondance ont été estimées. L'analyse multiéchelle a été utilisée pour caractériser les patrons du zooplancton aux différentes échelles spatiales (de l'échelle de l'habitat à celle du lagon tout entier) et pour identifier les processus responsables de ces structures spatiales. Cette étude a montré que la variabilité du zooplancton est un phénomène multiéchelle dont l'amplitude et la dépendance spatiale dépendent de la taille des organismes, de leur motilité et de la variable-réponse considérée (biomasse ou abondance). La biomasse et l'abondance du zooplancton varient en réponse à la distribution spatiale du phytoplancton, au comportement du zooplancton, à l'hétérogénéité de l'habitat, à l'hydrodynamique et aux évènements météorologiques. La nature et les effets de ces processus sont dépendants de l'échelle spatiale. Ce travail a montré comment le changement d'échelle spatiale met en évidence différents niveaux d'organisation de la communauté zooplanctonique en réponse à l'hétérogénéité environnementale.
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Ramakrishnan, Lakshmikantan. « Environmental variability and ecological dynamics in spatially structured populations / ». Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004361.
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ALVES, Amanda Lacerda. « Ecologia alimentar de Zoanthus sociatus e Protopalythoa variabilis (Cnidaria : Zoantharia) no litotal de Pernambuco, Brasil ». Universidade Federal Rural de Pernambuco, 2015. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5234.
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This study investigated the feeding ecology of zoanthids Zoanthus sociatus and Protopalythoa variabilis. Colonies of this species were sampled in the infralittoral zone of reefs in northeastern Brazil (may/2013 to february/2014). Polyps (n = 400) were examined the gastric cavity and prey found were counted, measured and identified. We calculated the richness and total abundance of prey items. The GLM test two-way ANOVA was used to compare the abundance and ricness between period and species. The biovolume of preys were calculated to characterize the most important food items in terms of their biomasses. To evaluate the selectivity, zoanthid and plankton samples were collected in the dry season and rainy. The results revealed the occurrence of seven taxa of phytoplankton and zooplankton three, and particulate organic matter. Pennales diatoms were the most abundant and most frequent prey and, together with invertebrate eggs, constituted the most important food items in terms of their biomasses. There were significant differences in abundance and richness among the species and between periods, with a significant interaction between these factors, only for abundance. The mean size of prey items within the polyps of Z. sociatus (26.35 ± 59.10 μm) and polyps of P. variabilis (26.56 ± 54.71 μm) was significantly smaller than in the plankton (54,14 ± 107,25 μm). As for the type prey, Zoanthus sociatus and Protopalythoa variabilis feed predominantly diatoms. The results, the two species are suspensívoras, feeding mainly on small phytoplankton. These results corroborate those previously found for the zoanthid P. caribaeorum in the same place, showing that this group has an important role in energy flow in reefs, transferring biomass of plankton to superiroes groups of the chain. This is fundamental to the Brazilian reefs where coverage of other suspensívoros as coral, is very low.
Este trabalho objetivou estudar a ecologia alimentar dos zoantídeos Zoanthus sociatus e Protopalythoa variabilis. Foram amostradas trimestralmente (maio/2013 a fevereiro/2014) colônias das espécies no infralitoral nos recifes da Praia de Porto de Galinhas (8º 33’ 00’’ a 8°33’33” S ; 35º 00’27’’ a 34º 59’ 00’’ W). Os pólipos (n=400) tiveram a cavidade gástrica examinada e as presas encontradas foram contabilizadas, medidas e identificadas. Foram calculadas a riqueza e abundância total dos itens de presas. O teste GLM two-way ANOVA foi usado para comparar a abundância e riqueza entre período e espécies. A partir das medições das presas, foi calculado o biovolume para caracterizar as presas com maior importância no aporte de biomassa. Para análise de seletividade foram coletadas amostras das espécies de zoantídeos e do plâncton no período seco e chuvoso. Os resultados revelaram a ocorrência de sete taxons do fitoplâncton e três do zooplâncton, além de matéria orgânica particulada. As diatomáceas pennales foram as presas mais abundantes e, juntamente, com ovos de invertebrados constituíram as presas mais importantes no aporte de biomassa. Houve diferença significativa na abundância e riqueza entre as espécies e entre os períodos, havendo interação significativa entre estes fatores, apenas para a abundância. O tamanho médio das presas presentes nos pólipos de Z. sociatus (26,35 ± 59,10 μm) e nos pólipos de P. variabilis (26,56 ± 54,71 μm) foi menor do que no plâncton (54,14 ± 107,25 μm). Quanto ao tipo de presa, Zoanthus sociatus e Protopalythoa variabilis se alimentam predominantemente de diatomáceas. Pelos resultados obtidos, as duas espécies são suspensívoras, alimentando-se principalmente de fitoplancton de pequeno porte. Esses resultados corroboram os anteriormente encontrados para o zoantídeo P. caribaeorum no mesmo local, demonstrando que este grupo tem um papel importantíssimo no fluxo de energia nos recifes, transferindo biomassa do plâncton para elos superiroes da cadeia. Isto é fundamental para os recifes brasileiros onde a cobertura de outros suspensívoros, como corais, é muito baixa.
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Gonzalez, Andrew. « Extinction : the role of habitat fragmentation and environmental variability ». Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/12032.
Texte intégralLivres sur le sujet "Ecologic variability"
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International Estuarine Research Conference (8th 1985 University of New Hampshire). Estuarine variability. Orlando, Fla : Academic Press, 1986.
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Moss, Michael R. Ecological crop productivity and climatic variability. [Guelph, Ont.] : Dept. of Geography, University of Guelph, 1993.
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Wiggert, Jerry D., Raleigh R. Hood, S. Wajih A. Naqvi, Kenneth H. Brink et Sharon L. Smith, dir. Indian Ocean Biogeochemical Processes and Ecological Variability. Washington, D. C. : American Geophysical Union, 2009. http://dx.doi.org/10.1029/gm185.
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1963-, Wiggert Jerry D., dir. Indian ocean biogeochemical processes and ecological variability. Washington, D.C : American Geophysical Union, 2009.
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Vasseur, D. A., et K. S. McCann, dir. The Impact of Environmental Variability on Ecological Systems. Dordrecht : Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-5851-6.
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J, Baird Donald, et Burton G. Allen, dir. Ecological variability : Separating natural from anthropogenic causes of ecosystem impairment. Pensacola, FL : SETAC Press, 2001.
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Jain, Meha. Adaptation to Climate Variability in Social Agro-Ecological Systems. [New York, N.Y.?] : [publisher not identified], 2014.
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W, Battarbee R., Gasse Françoise et Stickley Catherine E, dir. Past climate variability through Europe and Africa. Dordrecht, The Netherlands : Springer, 2004.
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Global Change Research Program (United States. Agricultural Research Service), dir. Forests, the potential consequences of climate variability and change. Washington, DC : U.S. Dept. of Agriculture, Global Change Program Office, 2001.
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name, No. Climate variability and ecosystem response at long-term ecological research sites. New York, NY : Oxford University Press, 2003.
Trouver le texte intégralChapitres de livres sur le sujet "Ecologic variability"
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Benedetti-Cecchi, Lisandro. « Environmental Variability ». Dans Ecological Studies, 127–41. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/b76710_9.
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Bendix, J., R. Rollenbeck, P. Fabian, P. Emck, M. Richter et E. Beck. « Climate Variability ». Dans Ecological Studies, 281–90. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-73526-7_27.
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Harris, Graham P. « Interannual variability ». Dans Phytoplankton Ecology, 291–327. Dordrecht : Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4081-9_12.
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Harris, Graham P. « Interannual variability ». Dans Phytoplankton Ecology, 291–327. Dordrecht : Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-3165-7_12.
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Honěk, A. « Variability and Genetic Studies ». Dans Ecology of Coccinellidae, 33–60. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-017-1349-8_3.
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Singh Saharan, Govind, Naresh Mehta et Prabhu Dayal Meena. « Pathogenic Variability ». Dans Alternaria Diseases of Crucifers : Biology, Ecology and Disease Management, 125–61. Singapore : Springer Singapore, 2015. http://dx.doi.org/10.1007/978-981-10-0021-8_6.
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O’Brien, Todd D., et Stephanie A. Oakes. « Visualizing and Exploring Zooplankton Spatio-Temporal Variability ». Dans Zooplankton Ecology, 192–224. First. | Boca Raton : CRC Press, [2021] : CRC Press, 2020. http://dx.doi.org/10.1201/9781351021821-11.
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Wiens, John A. « Coping with variability in environmental impact assessment ». Dans ECOtoxicology : Ecological Dimensions, 55–70. Dordrecht : Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-1541-1_6.
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Vandermeer, John, et Brian Schultz. « Variability, Stability, and Risk in Intercropping : Some Theoretical Explorations ». Dans Ecological Studies, 205–29. New York, NY : Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3252-0_14.
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Saharan, Govind Singh, Prithwi Raj Verma, Prabhu Dayal Meena et Arvind Kumar. « Physiologic Specialization (Pathogenic Variability) ». Dans White Rust of Crucifers : Biology, Ecology and Management, 133–50. New Delhi : Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-1792-3_8.
Texte intégralActes de conférences sur le sujet "Ecologic variability"
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Карманов, К., et K. Karmanov. « INVESTIGATION OF COASTAL VARIABILITY OF CURONIAN SPIT OF REMOTE SENSING DATA FROM 1963 TO 2011 ». Dans Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce3a5c0b265.50606307.
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Орвикку, К., K. Orvikku, Х. Тониссон et H. Tonisson. « SEA ICE AND ITS INFLUENCE TO COASTAL PROCESSES – BALTIC SEA, ESTONIA ». Dans Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce371f3f3a6.87362427.
Texte intégralRésumé :
The Baltic Sea region is characterized by variable winter weather conditions. Sea ice forms near the Estonian coast almost every winter and is characterized by large temporal and spatial variability [1, 2].
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Горячкин, Ю., et Yu Goryachkin. « VARIABILITY OF SEA LEVEL AND DYNAMICS THE ACCUMULATIVE COASTS OF WESTERN CRIMEA ». Dans Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce394b37220.57460895.
Texte intégralRésumé :
Influence of the sea level changes on the dynamics of accumulative coasts (in the region of the western Crimea) is considered. The data of observations shows that the greatest change of the beaches under the influence of the level changes by 1 cm can be 1, 3 m. However, the period for which it is determined (1989–2001) was characterized, firstly, by amplification of storm activity, and secondly, by substantial growth of deficiency in deposits. It has been caused by the new deep-water mooring in Eupatoria trading port, which has changed the local migration of deposits. The regular deepening of the waterway has resulted in change of their balance, adaptation of the coast to the changed conditions and, consequently, to acceleration of the coastal line abrasion. The weakest change of beaches under the influence of changes of the level by 1 cm, which is determined for the period 2006–2010, is 0,2–0,3 m. This period was characterized by relatively little changeability of storm activity and relative stabilization of anthropogenic influence, thus such figure seems to be more trustworthy.
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« Examining the Variability of Recycled Concrete Aggregate Properties ». Dans 4th International Conference on Advances in Agricultural, Biological & Ecological Sciences. International Institute of Chemical, Biological & Environmental Engineering, 2016. http://dx.doi.org/10.15242/iicbe.dir1216403.
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Kravtsova, N. E. « SPATIAL VARIABILITY OF INDICATORS OF THE PHOSPHORUS STATE OF CHERNOZEMS OF THE LOWER DON UNDER ». Dans STATE AND DEVELOPMENT PROSPECTS OF AGRIBUSINESS. DSTU-PRINT, 2020. http://dx.doi.org/10.23947/interagro.2020.1.172-174.
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The development of measures aimed at the rational use of the phosphate Fund of soils is relevant, especially in the ecological and agrochemical aspect. Studies of spatial variability of indicators of the phosphoric state of ordinary chernozems of the Lower don are carried out. A data Bank of indicators of the phosphorus regime of the studied soils was formed. It was found that high variability in the composition of mineral phosphates is more typical for arable horizons. Down the profile, the variability decreases. The lowest level of natural variability is observed in the AB horizon of the studied soils.
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Бобыкина, В., V. Bobykina, П. Жураховская et P. Zhurahovskaya. « SPATIAL AND TEMPORAL VARIABILITY OF GRANULOMETRIC COMPOSITION OF THE BALTIC (VISTULA) SPIT BEACHE SEDIMENTS ». Dans Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce374ed2651.42058449.
Texte intégralRésumé :
The beaches of the marine coast of the Baltic Spit are composed of medium size sand. granulometric differentiation of the beach sediment is observed around the perimeter from north to south. Changes in the composition suggest the existence of the flow of sediment from north to south. Comparison of changes in the fractional composition of sediments for the period 2004–2010 shows a trend of enlargement. This is due to the cessation of flow of anthropogenic deposits into the coastal zone.
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Крыленко, В., V. Krylenko, Р. Косьян, R. Kos'yan, М. Крыленко, M. Krylenko, А. Кочергин et A. Kochergin. « ANALYSIS OF THE MODERN GRAIN-SIZE COMPOSITION VARIABILITY OF THE ANAPA BAY-BAR BEACH SEDIMENTS ». Dans Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce3cd694162.92112428.
Texte intégralRésumé :
The results of realized in 2010 field researches of the spatial and time grain-size structure variability of beach and bottom sediments of the bay-bar Anapskaya southern part are presented in this paper. Irretrievable carrying out of sediment particles to depths more than 7 m intensifies with their size decrease to 0,1 mm. As over 70 % bottom and about 60 % beach sediments are presented by fractions less 0,16 mm on bay-bar Anapskaya southern part, namely at this part there is sand material massive carrying out to depth. Potential danger of the investigated site geosystem degradation is revealed.
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Piwowar, J., D. Peddle et D. Sauchyn. « Identifying Ecological Variability in Vegetation Dynamics Through Temporal Mixture Analysis ». Dans 2006 IEEE International Symposium on Geoscience and Remote Sensing. IEEE, 2006. http://dx.doi.org/10.1109/igarss.2006.965.
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Gordienko, I. « RESULT OF ANALYSIS OF DEPENDENCE OF THE NUMBER OF FULFILLED AND RUDIMENTARY LOTUS KOMAROV SEEDS ON THE SIZE OF SEED BOXES ». Dans Modern problems of animal and plant ecology. FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov, 2021. http://dx.doi.org/10.34220/mpeapw2021_108-111.
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The seeds collected from individually selected plants were studied according to the main linear parameters of morphological elements, the degree of variability and the presence of percentages. The main regularities between the linear dimensions of the seed elements and the size of the seed capsule containing them are revealed.
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Журминский, Сергей. « Характеристика отряда Charadriiformes фауны Республики Молдова ». Dans International symposium ”Actual problems of zoology and parasitology : achievements and prospects” dedicated to the 100th anniversary from the birth of academician Alexei Spassky. Institute of Zoology, Republic of Moldova, 2018. http://dx.doi.org/10.53937/9789975665902.103.
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Ecological fields of territorial units are populated by closely related species of birds by complimentary conditions. Their composition is determined by the form and power of contact of their areas with the territory, the stability of the links between them, the variability of the habitat, ecological features, adaptability and species strategy. In the sphere of interaction of these states take place a process of stabilizing communities in an unstable environment.
Rapports d'organisations sur le sujet "Ecologic variability"
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Brodie, Katherine, Ian Conery, Nicholas Cohn, Nicholas Spore et Margaret Palmsten. Spatial variability of coastal foredune evolution, part A : timescales of months to years. Engineer Research and Development Center (U.S.), juillet 2021. http://dx.doi.org/10.21079/11681/41322.
Texte intégralRésumé :
Coastal foredunes are topographically high features that can reduce vulnerability to storm-related flooding hazards. While the dominant aeolian, hydrodynamic, and ecological processes leading to dune growth and erosion are fairly well-understood, predictive capabilities of spatial variations in dune evolution on management and engineering timescales (days to years) remain relatively poor. In this work, monthly high-resolution terrestrial lidar scans were used to quantify topographic and vegetation changes over a 2.5 year period along a micro-tidal intermediate beach and dune. Three-dimensional topographic changes to the coastal landscape were used to investigate the relative importance of environmental, ecological, and morphological factors in controlling spatial and temporal variability in foredune growth patterns at two 50 m alongshore stretches of coast. Despite being separated by only 700 m in the alongshore, the two sites evolved differently over the study period. The northern dune retreated landward and lost volume, whereas the southern dune prograded and vertically accreted. The largest differences in dune response between the two sections of dunes occurred during the fall storm season, when each of the systems’ geomorphic and ecological properties modulated dune growth patterns. These findings highlight the complex eco-morphodynamic feedback controlling dune dynamics across a range of spatial scales.
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McKay, S. Is mean discharge meaningless for environmental flow management ? Engineer Research and Development Center (U.S.), septembre 2022. http://dx.doi.org/10.21079/11681/45381.
Texte intégralRésumé :
River ecosystems are highly dependent on and responsive to hydrologic variability over multiple time scales (e.g., hours, months, years). Fluctuating river flows present a key challenge to river managers, who must weigh competing demands for freshwater. Environmental flow recommendations and regulations seek to provide management targets balancing socio-economic outcomes with maintenance of ecological integrity. Often, flow management targets are based on average river conditions over temporal windows such as days, months, or years. Here, three case studies of hydrologic variability are presented at each time scale, which demonstrate the potential pitfalls of mean-based environmental flow criteria. Each case study shows that the intent of the environmental flow target is not met when hydrologic variability is considered. While mean discharge is inadequate as a single-minded flow management target, the consequences of mean flow prescriptions can be avoided in environmental flow recommendations. Based on these case studies, a temporal hierarchy of environmental flow thresholds is proposed (e.g., an instantaneous flow target coupled with daily and monthly averages), which would improve the efficacy of these regulations.
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Pruitt, Bruce, K. Killgore, William Slack et Ramune Matuliauskaite. Formulation of a multi-scale watershed ecological model using a statistical approach. Engineer Research and Development Center (U.S.), novembre 2020. http://dx.doi.org/10.21079/11681/38862.
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The purpose of this special report is to provide a statistical stepwise process for formulation of ecological models for application at multiple scales using a stream condition index (SCI). Given the global variability of aquatic ecosystems, this guidance is for broad application and may require modification to suit specific watersheds or stream reaches. However, the general statistical treatise provided herein applies across physiographies and at multiple scales. The Duck River Watershed Assessment in Tennessee was used, in part, to develop and test this multiscale, statistical approach; thus, it is considered a case example and referenced throughout this report. The findings of this study can be utilized to (1) prioritize water-sheds for restoration, enhancement, and conservation; (2) plan and conduct site-specific, intensive ecosystem studies; and (3) assess ecosystem outcomes (that is, ecological lift) applicable to future with and without restoration actions including alternative, feasibility, and cost-benefit analyses and adaptive management.
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Leis, Sherry, et Lloyd Morrison. Plant community trends at Tallgrass Prairie National Preserve : 1998–2018. National Park Service, octobre 2022. http://dx.doi.org/10.36967/2294512.
Texte intégralRésumé :
The Heartland Inventory and Monitoring Network monitors plant communities at Tallgrass Prairie National Preserve and evaluates a variety of environmental variables that affect vegetation patterns, including climate and ecological disturbances such as fire and grazing. Here we report on 2002–2018 trends in management actions (fire and grazing) and key plant community indicators. Temperature has increased over the past 50 years in the region. Precipitation and a standardized precipitation-evapotranspiration index included a high degree of interannual variability and did not demonstrate directional change. We documented a decline in disturbance intensity (i.e., less frequent prescribed fire and lower stocking rates) since 2006. A preserve goal is to maintain 30 to 60% of the area as bare ground (soil and rock) for ideal greater prairie-chicken habitat. Bare areas have been in decline and minimally meet the goal preserve wide. Bare areas vary by pasture and year, with bare areas exceeding the threshold in earlier years and Big Pasture and Red House Pasture falling short in some recent years. Although the preserve-scale mean minimally met the objective, there was a great deal of heterogeneity across monitoring sites. Litter cover and depth were greater than ecological recommendations for the greater prairie-chicken, especially in 2018. Litter depth demonstrated a great deal of variability and included deep litter. Woody plants were targeted to remain below 5% cover. Preserve- and pasture-scale cover means were well below this threshold but are increasing. Species richness on a per site basis (alpha diversity) and preserve-wide richness (gamma diversity) showed no apparent directional change when corrected for differences in sample size. Comparison of native species composition between 2002 and 2018 revealed a 36.9% difference in the Sørensen Index, although observer error accounted for almost 2/3 of this apparent change. The preserve continues to have characteristic tallgrass prairie species, and nonnative species continue to be low. Similar to targeted invasive plant monitoring, we found the target species Kentucky bluegrass to be below park thresholds. Continued evaluation of fire frequency and grazing intensity will be critical to achieving ecological goals including conserving the greater prairie-chicken. Development of a grazing plan may assist with prescribing stocking rates that are consistent with the preserve’s ecological and cultural objectives and could include alternative herbivores, such as goats or expansion of bison.
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Wyndham, Amber, Emile Elias, Joel Brown, Michael Wilson et Albert Rango. Drought Vulnerability Assessment to Inform Grazing Practices on Rangelands of Southeastern Colorado’s Major Land Resource Area 69. USDA Southwest Climate Hub, juillet 2018. http://dx.doi.org/10.32747/2018.6947062.ch.
Texte intégralRésumé :
Increased climate variability, including more frequent and intense drought, is projected for the southwestern region of the United States. Increased temperatures and reduced precipitation lower soil water availability, resulting in decreased plant productivity and altering species composition, which may affect forage quality and quantity. Reduced forage quality and increased heat stress attributable to warmer temperatures could lead to decreased livestock performance in this system, which is extensively used for livestock grazing. Mitigating the effects of increasing drought is critical to social and ecological stability in the region. Reduced stocking rates, change in livestock breeds and/or grazing practices
are general recommendations that could be implemented to cope with increased climatic stress. Ecological Sites and their associated state–and-transition models (STMs) are tools to help land managers implement and evaluate responses to disturbances. The projected change in climate will vary depending upon geographic location. Vulnerability assessments and adaptation strategies are needed at the local level to inform local management decisions and help ameliorate the effects of climate change on rangelands. The United States Department of Agriculture (USDA) Southwest Climate Hub and Natural Resources Conservation Service (NRCS) worked together to produce this drought vulnerability
assessment at the Major Land Resource Area (MLRA) level, based on ecological sites and state-and-transition models that will help landowners and government agencies to identify and develop adaptation options for drought on rangelands. The assessment illustrates how site-specific information can be used to help minimize the effects of drought on rangelands and support informed decision-making for the selection of management adaptations within MLRA 69.
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Wyndham, Amber, Emile Elias, Joel R. Brown, Michael A. Wilson et Albert Rango. Drought Vulnerability Assessment to Inform Grazing Practices on Rangelands in Southeast Arizona and Southwest New Mexico’s Major Land Resource Area 41. United States. Department of Agriculture. Southwest Climate Hub, août 2018. http://dx.doi.org/10.32747/2018.6818230.ch.
Texte intégralRésumé :
Increased climate variability, including more frequent and intense drought, is projected for the southwestern region of the United States. Increased temperatures and reduced precipitation lower soil water availability, resulting in decreased plant productivity and altered species composition, which may affect forage quality and quantity. Reduced forage quality and increased heat stress attributable to warmer temperatures could lead to decreased livestock performance in this system, which is extensively used for livestock grazing. Mitigating the effects of increasing drought is critical to social and ecological stability in the region. Reduced stocking rates and/or a change in livestock breeds and/or grazing practices are general recommendations that could be implemented to cope with increased climatic stress. Ecological Sites (ESs) and their associated state-and-transition models (STMs) are tools to help land managers implement and evaluate responses to disturbances. The projected change in climate will vary depending upon geographic location. Vulnerability assessments and adaptation strategies are necessary at the local level to inform local management decisions and help to ameliorate the effects of climate change on rangelands. The USDA Southwest Climate Hub and the Natural Resources Conservation Service (NRCS) worked together to produce this drought vulnerability assessment at the Major Land Resource Area (MLRA) level: it is based on ESs/STMs that will help landowners and government agencies to identify and develop adaptation options for drought on rangelands. The assessment illustrates how site-specific information can be used to help minimize the effects of drought on rangelands and to support informed decision-making for selecting management adaptations within MLRA 41.
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Wyndham, Amber, Emile Elias, Joel R. Brown, Michael A. Wilson et Albert Rango. Drought Vulnerability Assessment to Inform Grazing Practices on Rangelands of Southeastern Colorado’s Major Land Resource Area 69. United States. Department of Agriculture. Southwest Climate Hub, janvier 2018. http://dx.doi.org/10.32747/2018.6876399.ch.
Texte intégralRésumé :
Increased climate variability, including more frequent and intense drought, is projected for the southwestern region of the United States. Increased temperatures and reduced precipitation lower soil water availability resulting in decreased plant productivity and altering species composition which may affect forage quality and quantity. Reduced forage quality and increased heat stress attributable to warmer temperatures could lead to decreased livestock performance in this system, which is extensively used for livestock grazing. Mitigating the effects of increasing drought is critical to social and ecological stability in the region. Reduced stocking rates, change in livestock breeds and/or grazing practices are general recommendations that could be implemented to cope with increased climatic stress. Ecological Sites (ESs) and their associated state and transition models (STMs) are tools to help land managers implement and evaluate responses to disturbances. The projected change in climate will vary depending on geographic location. Vulnerability assessments and adaptation strategies are needed at the local level to inform local management decisions and help ameliorate the effects of climate change on rangelands. The USDA Southwest Climate Hub and Natural Resources Conservation Service (NRCS) worked together to produce this drought vulnerability assessment at the Major Land Resource Area (MLRA) level based on ESs/STMs that will help landowners and government agencies identify and develop adaptation options for drought on rangelands. The assessment illustrates how site-specific information can be used to help minimize the effects of drought on rangelands and support informed decision-making for selecting management adaptations within MLRA 69.
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Wyndham, Amber, Emile Elias, Joel Brown, Michael Wilson et Albert Rango Rango. Drought Vulnerability Assessment to Inform Grazing Practices on Rangelands in Southeast Arizona and Southwest New Mexico’s Major Land Resource Area 41. USDA Southwest Climate Hub, août 2018. http://dx.doi.org/10.32747/2018.6947060.ch.
Texte intégralRésumé :
Increased climate variability, including more frequent and intense drought, is projected for the southwestern region of the United States. Increased temperatures and reduced precipitation lower soil water availability, resulting in decreased plant productivity and altered species composition, which may affect forage quality and quantity. Reduced forage quality and increased heat stress attributable to warmer temperatures could lead to decreased livestock performance in this system, which is extensively used for livestock grazing. Mitigating the effects of increasing drought is critical to social and ecological stability in the region. Reduced stocking rates and/or a change in livestock breeds and/or grazing
practices are general recommendations that could be implemented to cope with increased climatic stress. Ecological Sites (ESs) and their associated state-and-transition models (STMs) are tools to help land managers implement and evaluate responses to disturbances. The projected change in climate will vary depending upon geographic location. Vulnerability assessments and adaptation strategies are necessary at the local level to inform local management decisions and help to ameliorate the effects of climate change on rangelands. The USDA Southwest Climate Hub and the Natural Resources Conservation Service (NRCS) worked together to produce this drought vulnerability assessment at the
Major Land Resource Area (MLRA) level: it is based on ESs/STMs that will help landowners and government agencies to identify and develop adaptation options for drought on rangelands. The assessment illustrates how site-specific information can be used to help minimize the effects of drought on rangelands and to support informed decision-making for selecting management adaptations within MLRA 41.
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Wyndham, Amber, Emile Elias, Joel Brown, Michael Wilson et Albert Rango. Drought Vulnerability Assessment to Inform Grazing Practices on Rangelands of Southeastern Colorado’s Major Land Resource Area 69. USDA Southwest Climate Hub, mars 2018. http://dx.doi.org/10.32747/2018.6965584.ch.
Texte intégralRésumé :
Increased climate variability, including more frequent and intense drought, is projected for the southwestern region of the United States. Increased temperatures and reduced precipitation lower soil water availability resulting in decreased plant productivity and altering species composition which may affect forage quality and quantity. Reduced forage quality and increased heat stress attributable to warmer temperatures could lead to decreased livestock performance in this system, which is extensively used for livestock grazing. Mitigating the effects of increasing drought is critical to social and ecological stability in the region. Reduced stocking rates, change in livestock breeds and/or grazing practices are general recommendations that could be implemented to cope with increased climatic stress. Ecological Sites (ESs) and their associated state and transition models (STMs) are tools to help land managers implement and evaluate responses to disturbances. The projected change in climate will vary depending on geographic location. Vulnerability assessments and adaptation strategies are needed at the local level to inform local management decisions and help ameliorate the effects of climate change on rangelands. The USDA Southwest Climate Hub and Natural Resources Conservation Service (NRCS) worked together to produce this drought vulnerability assessment at the Major Land Resource Area (MLRA) level based on ESs/STMs that will help landowners and government agencies identify and develop adaptation options for drought on rangelands. The assessment illustrates how site-specific information can be used to help minimize the effects of drought on rangelands and support informed decision-making for selecting management adaptations within MLRA 69.
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Aalto, Juha, et Ari Venäläinen, dir. Climate change and forest management affect forest fire risk in Fennoscandia. Finnish Meteorological Institute, juin 2021. http://dx.doi.org/10.35614/isbn.9789523361355.
Texte intégralRésumé :
Forest and wildland fires are a natural part of ecosystems worldwide, but large fires in particular can cause societal, economic and ecological disruption. Fires are an important source of greenhouse gases and black carbon that can further amplify and accelerate climate change. In recent years, large forest fires in Sweden demonstrate that the issue should also be considered in other parts of Fennoscandia. This final report of the project “Forest fires in Fennoscandia under changing climate and forest cover (IBA ForestFires)” funded by the Ministry for Foreign Affairs of Finland, synthesises current knowledge of the occurrence, monitoring, modelling and suppression of forest fires in Fennoscandia. The report also focuses on elaborating the role of forest fires as a source of black carbon (BC) emissions over the Arctic and discussing the importance of international collaboration in tackling forest fires. The report explains the factors regulating fire ignition, spread and intensity in Fennoscandian conditions. It highlights that the climate in Fennoscandia is characterised by large inter-annual variability, which is reflected in forest fire risk. Here, the majority of forest fires are caused by human activities such as careless handling of fire and ignitions related to forest harvesting. In addition to weather and climate, fuel characteristics in forests influence fire ignition, intensity and spread. In the report, long-term fire statistics are presented for Finland, Sweden and the Republic of Karelia. The statistics indicate that the amount of annually burnt forest has decreased in Fennoscandia. However, with the exception of recent large fires in Sweden, during the past 25 years the annually burnt area and number of fires have been fairly stable, which is mainly due to effective fire mitigation. Land surface models were used to investigate how climate change and forest management can influence forest fires in the future. The simulations were conducted using different regional climate models and greenhouse gas emission scenarios. Simulations, extending to 2100, indicate that forest fire risk is likely to increase over the coming decades. The report also highlights that globally, forest fires are a significant source of BC in the Arctic, having adverse health effects and further amplifying climate warming. However, simulations made using an atmospheric dispersion model indicate that the impact of forest fires in Fennoscandia on the environment and air quality is relatively minor and highly seasonal. Efficient forest fire mitigation requires the development of forest fire detection tools including satellites and drones, high spatial resolution modelling of fire risk and fire spreading that account for detailed terrain and weather information. Moreover, increasing the general preparedness and operational efficiency of firefighting is highly important. Forest fires are a large challenge requiring multidisciplinary research and close cooperation between the various administrative operators, e.g. rescue services, weather services, forest organisations and forest owners is required at both the national and international level.