The Experts below are selected from a list of 189237 Experts worldwide ranked by ideXlab platform
Lauri Oksanen - One of the best experts on this subject based on the ideXlab platform.
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trophic levels and trophic dynamics a consensus emerging
Trends in Ecology and Evolution, 1991Co-Authors: Lauri OksanenAbstract:Abstract There are three clearly different views on trophic levels. The systems-Ecological tradition sees trophic levels as relatively discrete and well-defined units whose interactions cannot be derived from interactions between constituent Populations. The reductionist Population-Ecological tradition sees trophic levels as inappropriate abstractions that cannot be used in formulating predictive theories. The tradition of trophic dynamics sees the first three trophic levels of autotroph-based ecosystems as reasonable abstractions, useful in formulating predictive theories, but devoid of properties that could not be directly extrapolated from those of constituent Populations. Recent literature suggests that the first two schools are converging towards the viewpoints of the third, though the latter has also been modified by the interaction.
Zhang Chang-ik - One of the best experts on this subject based on the ideXlab platform.
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A Study on the Stock Assessment and Management Implications of the Hairtail, Trichiurus lepturus Linne in Korean Waters 1. Estimation of Population Ecological Characteristics of the Hairtail, Trichiurus lepturus Linne in Korean Waters
Korean Journal of Fisheries and Aquatic Sciences, 1996Co-Authors: Zhang Chang-ikAbstract:This study is to estimate Population Ecological parameters, including growth parameters, survival rates, instantaneous coefficients of natural and fishing mortalities, and age at first capture, as well as growth rates at age of the hairtail, Trichiurus lepturus Linne in Korean waters. For describing the growth of the hairtail, three growth models were fitted, and the von Bertalanffy growth model was adopted for the purpose of the further stock assessment work. The von Bertalanffy growth parameters estimated from a nonlinear regression using EXCEL Solver were , K=0.3868, and . Annual survival rate (S) of the hairtail was estimated to be 0.277 (variance=0.00035) and the instantaneous coefficient of natural mortality (M) was estimated to be 0.441/year. Instantaneous coefficient of fishing mortality (F) for the recent years was calculated as 0.843/year, implying an impact from fishing about two times greater than that of natural mortality. The age at first capture was estimated to be 0.787 years, which is much younger age than mature age. Finally, the growth rates at age were estimated.
Arndt Hampe - One of the best experts on this subject based on the ideXlab platform.
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Plants on the move: the role of seed dispersal and initial Population establishment for climate-driven range expansions
Acta Oecologica, 2011Co-Authors: Arndt HampeAbstract:Recent climate change will presumably allow many plant species to expand their geographical range up to several hundred kilometres towards the poles within a few decades. Much uncertainty exists however to which extent species will actually be able to keep pace with a rapidly changing climate. A suite of direct and indirect research approaches have explored the phenomenon of range expansions, and the existing evidence is scattered across the literature of diverse research subdisciplines. Here I attempt to synthesise the available information within a Population Ecological framework in order to evaluate implications of patterns of seed dispersal and initial Population establishment for range expansions. After introducing different study approaches and their respective contributions. I review the empirical evidence for the role of long-distance seed dispersal in past and ongoing expansions. Then I examine how some major Ecological determinants of seed dispersal and colonisation processes - Population fecundity, dispersal pathways, arrival site conditions, and biotic interactions during recruitment - could be altered by a rapidly changing climate. While there is broad consensus that long-distance dispersal is likely to be critical for rapid range expansions, it remains challenging to relate dispersal processes and pathways with the establishment of pioneer Populations ahead of the continuous species range. Further transdisciplinary efforts are clearly needed to address this link, key for understanding how plant Populations 'move' across changing landscapes.
Christian Damgaard - One of the best experts on this subject based on the ideXlab platform.
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Integrating hierarchical statistical models and machine learning algorithms for ground-truthing drone images of the vegetation: taxonomy, abundance and Population Ecological models
2018Co-Authors: Christian DamgaardAbstract:In order to fit Population Ecological models, e.g. plant competition models, to the new drone-aided image data, we need to develop statistical models that may take the new type of measurement uncertainty into account and quantify its importance for statistical inferences and Ecological predictions. Here, it is proposed to quantify the uncertainty and bias of image predicted plant taxonomy and abundance in a hierarchical statistical model that is linked to ground-truth data obtained by the pinpoint method. It is critical that the error rate in the species identification process is minimized when the image data are fitted to the Population Ecological models, and several avenues for reaching this objective are discussed.
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Competitive interactions and the effect of herbivory on Bt‐Brassica napus, Brassica rapa and Lolium perenne
Journal of Applied Ecology, 2009Co-Authors: Christian Damgaard, Christian KjærAbstract:Summary 1. The probability of a transgenic crop establishing a feral Population outside cultivated areas and possibly outcompeting naturally occurring species needs to be assessed to make an Ecological risk assessment of the transgenic crop. 2. The interaction between herbivory and competition is thought to determine the Ecological success of insect-resistant plants, and this interaction was investigated in a competition experiment with transgenic insect-resistant Bt-Brassica napus, Brassica rapa, Lolium perenne, and herbivory from the large white butterfly Pieris brassicae. 3. As expected, herbivory had a negative effect on the biomass of B. rapa at high plant densities. The competitive ability of L. perenne, when growing with B. rapa, increased significantly with the level of herbivory on B. rapa. 4. To predict the effect of herbivory in a natural ecosystem, plant competition between the two annual Brassica species was analysed in a Population Ecological model. It was concluded that it is probable that transgenic Bt-B. napus plants may invade a natural habitat if herbivory is sufficiently high and the habitat is suitable for B. napus. 5. Synthesis and applications. The results indicate that it is important to study the interaction between herbivory and competition when assessing the Ecological risk of insect-resistant genetically modified crops. Furthermore, combining Ecological data from manipulated experiments with Population Ecological modelling is a fruitful approach when conducting environmental risk assessments.
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Evolution of advantageous alleles affecting Population Ecological characteristics in partially inbreeding Populations
Hereditas, 2003Co-Authors: Christian DamgaardAbstract:The fate of advantageous alleles affecting intrinsic growth rate, carrying capacity or intra-specific competitive ability was examined in a partially inbreeding Population. Generally, inbreeding had an effect on the evolution of advantageous alleles affecting Population Ecological characteristics. For example, in a specific underdominant case the number of stable internal equilibria decreased from two to one with only a slight degree of inbreeding. Equilibrium frequencies of stable internal equilibria and stability of fixation equilibria were also affected by the degree of inbreeding. For strictly advantageous alleles, inbreeding had the same qualitative effect on the fixation probability and mean fixation time as predicted in simpler selection models.
Christopher P Brooks - One of the best experts on this subject based on the ideXlab platform.
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Assessment and Prediction of the Effects of Highways on Population Ecological and Genetic Properties of Selected Faunal Groups: The Consequences of Breakup and Isolation
2005Co-Authors: Alan E Stiven, Christopher P BrooksAbstract:The focus of this study was to identify features of amphibian species and roads that might serve as predictors of future sensitivity to habitat fragmentation. To accomplish this task 134 sites were sampled primarily in the Piedmont region of North Carolina using both active and passive methods. In those sites animals were collected throughout the study period (Aug 2000 - Dec 2002). A significant drought (rainfall deficit > 14 in.) event spanned the entire study period. The low number of animals is likely a result of the high mortalities and low activity levels displayed by amphibians during drought conditions. Here we provide an extensive review of the literature dealing with roads as barriers to amphibian movement. Patterns derived from the literature provide a framework for the recommendations made in this report. Also included is a manuscript (in press) that describes a model dealing with the nature of habitat fragmentation and barriers. This paper was the framework for the interpretation of the genetic analysis and is the focus of ongoing study in our laboratory.