| 1. |
- Abrahamsson, Otto, et al.
(författare)
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Modelling seasonal flow variability of European rivers
- 1998
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Ingår i: Ecological Modelling. - 0304-3800 .- 1872-7026. ; 114:1, s. 49-58
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Tidskriftsartikel (refereegranskat)abstract
- River discharge influences many important processes in a lake ecosystem. For example, the tributary discharge is one of the major regulating factors for the lake water retention time and, hence, the retention of substances in lake water. However, river discharge depends on many more or less stochastic processes, which makes it difficult to give a reliable prediction of the discharge for a specific river at a given time. This paper presents an attempt to overcome many of those difficulties with a simple mathematical model. The model was designed to meet some specific demands for ecosystem modelling of contaminating substances. The most important of those requirements is that the model had to be based on readily available driving variables, preferably from standard maps. The presented results are based on extensive calibrations and validations using empirical data on monthly water discharge from more than 200 European rivers. It may be concluded that this model yields predictions that capture the essential components in mean monthly variations in river discharge in European rivers and that this model is driven by easily available driving variables like catchment area, mean annual precipitation, altitude, and latitude. The technique to obtain seasonal variability is based on calibrated ‘norms’ and smoothing functions defined from the driving variables.
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| 2. |
- Colding, Johan
(författare)
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Analysis of hunting options by the use of general food taboos
- 1998
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Ingår i: Ecological Modelling. - 0304-3800 .- 1872-7026. ; 110:1, s. 5-17
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Tidskriftsartikel (refereegranskat)abstract
- A hypothetical model was built, using the STELLA II software program, to test several hunting options for a human hunting group. Different outcomes of possible hunting modes are analysed, such as a change in hunting rate, prey hunted, or species avoided or not avoided by taboos. The model consists of five sectors that reflect a short food chain in an upper Amazonian ecosystem. There is a vegetation sector, a predator sector, and two sectors consisting of browsers and grazers. The last sector represents a human group, known as the Ecuador Achuar. The critical factor analysed is how differences in hunting rate affect a target resource, and how this resource may be affected by general food taboos. The major results of the model are that general food taboos may not be an adaptive short term strategy for hunters, but that a 'moderate' hunting mode may be the most effective option for the human group. Since the model is a simplification of the real world, no general conclusions for management should be drawn from the results.
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| 3. |
- Kumblad, Linda, et al.
(författare)
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An ecosystem model of the environmental transport and fate of carbon-14 in a bay of the Baltic Sea, Sweden
- 2003
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Ingår i: Ecological Modelling. - : Elsevier. - 0304-3800 .- 1872-7026. ; 166:3, s. 193-210
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Tidskriftsartikel (refereegranskat)abstract
- The environmental transport and fate of a hypothetical discharge of radioactive C-14 from the Swedish final repository for radioactive operational waste (SFR) was investigated using an ecosystem modelling approach. It involved identification, quantification and dynamic modelling of the main flows and storages of carbon both in the physical environment and in the food web of a bay in the Baltic Sea. In the model, C-14 was introduced into the food web via photosynthesising organisms. Contamination of the modelled ecosystem was assessed assuming a release of 51.3 MBq per year for 1000 years. The implications of changes of two parameters on the C-14 fate were examined: route of C-14 entry in the food web and water exchange. Modelling results were also used to estimate steady-state C-14-concentrations in biota, to investigate the time needed to reach steady-state and to calculate the ecological half-life of the radionuclide for the modelled compartments and the ecosystem. Since the modelled area is characterised by a fast water exchange, most of the discharged C-14 was flushed out of the system (99.8%), and diluted in a much larger recipient. However, a small fraction of the discharge was assimilated by primary producers, which enabled subsequent transfer of C-14 to organisms at higher trophic levels (e.g. fish, seals and humans). In general, the highest C-14-concentrations were observed in benthic plants and benthic macrograzers followed by fish and other organisms. An assumption of C-14 entry into the food web via benthic primary producers was found to lead to increased concentrations in-biota (especially benthic organisms) and reduced rates of water exchange were also observed to significantly increase the C-14 exposure of the organisms.
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| 4. |
- Repsilber, Dirk, 1971-, et al.
(författare)
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Spatial genetic patterns systematically accelerate and bias drift-based genetic erosion
- 2002
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Ingår i: Ecological Modelling. - Amsterdam, Netherlands : Elsevier. - 0304-3800 .- 1872-7026. ; 148:3, s. 251-261
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Tidskriftsartikel (refereegranskat)abstract
- Genetic erosion of an ecosystem’s key species weakens the basis of ecosystem stability. In the absence of selection and migration genetic drift is the only factor influencing the degree of genetic erosion. Populations of sessile organisms represent a pattern of genetic information in space. In this paper, we show how spatial genetic patterns bias and accelerate the dynamics of drift-based genetic erosion. Using a Cellular Automaton (CA) as a modeling environment for discrete systems with local dynamics, we study the boundary conditions for such pattern-dependent genetic erosion. The system is designed as a one locus two allele model for haploid loci. Each cell in the CA represents one sessile individual of the simulated population. In order to analyze the behavior of the model we varied the following four variables, (1) the initial spatial distribution of haplotypes; (2) the magnitude of local gene-flow; (3) the noise in the initial pattern and; (4) the intensity of global (non-local) gene-flow. We show that for certain spatial genetic patterns genetic drift systematically leads to the fixation of one allele, if the size of the patterns and the dimension of local gene flow are of similar scale. Moreover, drift is substantially accelerated compared to the situation, where the two alleles are randomly distributed. These results are rather stable to noise in the initial pattern but external gene flow (EGF) has to be limited to a certain threshold to allow spatial patterns to drive genetic erosion.
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| 5. |
- Westerberg, Lars, et al.
(författare)
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Predicting the spatial distribution of a population in a heterogeneous landscape
- 2003
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Ingår i: Ecological Modelling. - 0304-3800 .- 1872-7026. ; 166:1-2, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- A spatially explicit, population-based density-independent matrix model was used to analyse the effect of landscape composition on the spatial asymptotic distribution of a population. The landscape was considered being continuous rather than consisting of patches. The redistribution of a population was viewed in a simplistic way, and modelled using a response function to local landscape quality and a displacement function. Hence, the approach is suitable for landscape ecologists. Some of the analytical methods from non-negative matrix theory were used to determine the differences between the asymptotical spatial population distribution (the dominating right eigenvector of the movement matrix) and the randomly arranged resources. The results showed that the amount and quality of poor habitats had the greatest impact on matching between population and resource distribution. The results on matching between population and resource distribution are discussed in relation to designing reserves for endangered species and in the biocontrol of pest species in agricultural systems. © 2003 Elsevier Science B.V. All rights reserved.
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| 6. |
- Pommerening, Arne
(författare)
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A new nearest-neighbour index for monitoring spatial size diversity: The hyperbolic tangent index
- 2020
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 435
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Tidskriftsartikel (refereegranskat)abstract
- Understanding natural mechanisms of maintaining diversity is a crucial pre-requisite for successfully mitigating adverse effects of climate change such as the loss of diversity. To make such an understanding possible, both experiments and an effective, continued monitoring of diversity are required. Recently spatial measures of plant diversity have greatly contributed to the quality of diversity monitoring. In this article, we first reviewed existing principles of nearest-neighbour index construction and on this basis introduced a new spatially explicit size diversity index that is based on trigonometry, i.e. the hyberbolic tangent index. We discussed the index' mathematical reasoning by explaining its relationship to individual-based modelling and to other size diversity construction principles. Then we demonstrated the usefulness of the hyperbolic tangent index in indicating important interspecific relationships in mixed-species forest ecosystems. As part of studying the behaviour of the new size diversity construction principle we additionally found that there is a high correlation between the hyberbolic tangent index and absolute growth rates, i.e. the index is suitable both as a diversity and a competition index. Finally a detailed correlation analysis in a Norway spruce forest ecosystem with tree densities between 590 and 3800 trees per hectare made us understand that in most cases 7-10 neighbours are sufficient to consider when calculating the hyperbolic tangent index for explaining absolute growth rates. When using the index as an indicator of plant diversity only, smaller numbers of nearest neighbours may suffice. The index is straightforward to apply even, if the monitoring system used involves small circular sample plots.
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| 7. |
- An, Li, et al.
(författare)
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Challenges, tasks, and opportunities in modeling agent-based complex systems
- 2021
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 457
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Forskningsöversikt (refereegranskat)abstract
- Humanity is facing many grand challenges at unprecedented rates, nearly everywhere, and at all levels. Yet virtually all these challenges can be traced back to the decision and behavior of autonomous agents that constitute the complex systems under such challenges. Agent-based modeling has been developed and employed to address such challenges for a few decades with great achievements and caveats. This article reviews the advances of ABM in social, ecological, and socio-ecological systems, compare ABM with other traditional, equation-based models, provide guidelines for ABM novice, modelers, and reviewers, and point out the challenges and impending tasks that need to be addressed for the ABM community. We further point out great opportunities arising from new forms of data, data science and artificial intelligence, showing that agent behavioral rules can be derived through data mining and machine learning. Towards the end, we call for a new science of Agent-based Complex Systems (ACS) that can pave an effective way to tackle the grand challenges.
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| 8. |
- An, Li, et al.
(författare)
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Corrigendum to “Challenges, tasks, and opportunities in modeling agent-based complex systems”, Ecological Modeling, 2021, 457 : 109,685, page 1–15 (Ecological Modelling (2021) 457, (S030438002100243X), (10.1016/j.ecolmodel.2021.109685))
- 2022
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 471
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Tidskriftsartikel (refereegranskat)abstract
- DOI of original article: 10.1016/j.ecolmodel.2021.109685. The authors regret that the following references are missing from the original article's online supplementary information: Box, P., 2001. Kenge GIS-CA class template for Swarm. Nat. Resour. Environ. Issues 8, 31–35. Minar, A., Burkhart, R., Langton, C.G., Manor, A., 1996. The Swarm simulation system: A toolkit for building multi-agent simulations (SFI Working paper No. 96- 06–042). Santa Fe Institute, Santa Fe, NM. Wilensky, U., Rand, W., 2015. An introduction to agent-based modeling: modeling natural, social, and engineered complex systems with NetLogo. MIT Press, Cambridge, MA. The authors would like to apologize for any inconvenience caused.
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| 9. |
- Andren, Henrik, et al.
(författare)
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Using citizen data in a population model to estimate population size of moose (Alces alces)
- 2022
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 471
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Tidskriftsartikel (refereegranskat)abstract
- Long-term and wide-ranging citizen science programs provide a unique opportunity to monitor wildlife populations and trends through time while encouraging stakeholder participation, engagement, and trust. Hunter observations is such a program that in Sweden is used on a regular basis to monitor population trends of moose. However, hunter observations are not reliable to determine the actual population size. We developed a mechanistic moose population model that integrated citizen science data and used it at various geographical scales to estimate moose population size between 2012 and 2020. A sensitivity analysis, specifically performed for recruitment, adult sex ratio and calf sex ratio, showed that the simulated population size was most sensitive for variation in recruitment. According to the results, Sweden had a total moose population of -311 000 (+/- 4%) individuals pre-hunt and -228 000 (+/- 4%) post-hunt in 2020. The post-hunt moose abundance has decreased nationwide with 15%, from 0.72 to 0.61 moose per km2 during the 2012 - 2020 period. The present post-hunt moose density was estimated at 0.39, 0.78, 0.84 and 0.54 per km2 for the regions northernmost, northern, central and southern Sweden, respectively. The simulation model can be used for strategic and operative management at various geographical scales and is publicly available. By integrating citizen data with a mechanistic population model, a new low-cost method of estimating population size and relevant population dynamics was established.
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| 10. |
- Beven, Keith
(författare)
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What we see now : Event-persistence and the predictability of hydro-eco-geomorphological systems
- 2015
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 298:SI, s. 4-15
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Tidskriftsartikel (refereegranskat)abstract
- What we see now in the landscape is the result of a long history of events with varying degrees of persistence. We have only limited access to much of that history and we know that many current events have only a minimal impact on what we see. Even rather extreme events may have impacts that are not very long-lasting but can have the effect of changing the antecedent states for future events. That means that sampling of sequences of events might be important in understanding the evolution of the catchments. In some cases, however, extreme events can have an impact on the system that persists over hundreds or thousands of years. Any evolution of the landscape is then constrained by those past events, however much it might be also constrained by self-organisational principles. It might be difficult to verify those principles given the epistemic uncertainties about past histories and system properties that are generic to the studies that are possible within a research project or career. These arguments are investigated in a simple slab model of landslip failures in a hillslope hollow subject to stochastic forcing over long periods of time. The complementarity of an event-persistence approach to hydro-eco-geomorphological systems is captured in suggestions for future research questions.
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