| 1. |
- Alveteg, Mattias, et al.
(författare)
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Evaluating simplifications used in regional applications of the SAFE and MAKEDEP models
- 1998
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Ingår i: Ecological Modelling. - 0304-3800. ; 107:2-3, s. 265-277
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Tidskriftsartikel (refereegranskat)abstract
- The importance of different additional simplifications used when moving from single site applications to regional applications of the SAFE and MAKEDEP models was studied. The SAFE model is a dynamic soil chemistry model, which apart from physical and chemical soil parameters also needs the historic evolution of atmospheric deposition and nutrient uptake to simulate the effects of acidic deposition on the chemical status of forest soils. The historic evolution of atmospheric deposition and nutrient uptake are reconstructed by the MAKEDEP model, using information on current deposition and nutrients status together with general deposition trends. Additional simplifica- tions are enforced by limitations in available regional data sets and the costs involved in completing regional data sets. The simplifications studied here are the same as those used in an actual regional application to Scania, southern Sweden: (1) Use of default values for certain soil parameters such as dissolved organic carbon (DOC) and soil bulk density; (2) Use of general depth trends to extrapolate soil parameters, such as mineralogy and surface area, measured for one soil layer to the other three soil layers considered in the SAFE model application; (3) Use of a simplified version of MAKEDEP, where some of the key feedbacks, such as the effects of a growing canopy on dry deposition rates have been removed in order to limit the input data needed to run the MAKEDEP model. The models where applied to two well documented sites, Solling, Germany and Rothamsted, UK. Model results using the above simplifications and subsets thereof were compared with soil chemistry measurements and model results based on previously published single-site applications for the two sites. The study shows that the trends and the present day values of pH and base cation concentration are reproduced fairly well even when all of the simplifications are used. In order to increase the reliability of the regional applications, however, the non-simplified version of MAKEDEP should be used rather than the simplified version. Regional data sets of standing biomass and nutrient contents are therefore needed.
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| 2. |
- Bobba, A. G., et al.
(författare)
-
Application of environmental models to different hydrological systems
- 2000
-
Ingår i: Ecological Modelling. - 0304-3800. ; 125:1, s. 15-49
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Tidskriftsartikel (refereegranskat)abstract
- In recent years global problems such as climatic change, acid rain, and water pollution in surface and subsurface environments dominate discussions of world environmental problems. In this paper, the roles of hydrologic processes and hydrogeochemical processes are investigated through development, modification, and application of mathematical models for addressing point and non-point source water quality modelling of receiving waters: surface water, subsurface water and lake water. The paper describes the use of models to simulate the movements of pollutants and water: subsurface water, surface water and lake sediments. A hydrological model was applied to Northeast Pond River watershed to understand climate change effects in the watershed. Four watershed acidification models were applied to compute hydrogen ion, alkalinity and sulphate concentrations from Turkey Lakes watershed, Canada. The computed hydrogen ion was used to estimate acidic events, magnitude of hydrogen ion, and duration using a stochastic model. There exist uncertainties in environmental models due to imperfect knowledge of processes controlling water quality parameters as well as errors in data. Monte Carlo, first order, and inverse method analyses were used to assess uncertainty in models. SUTRA (saturated-unsaturated transport) and SUTRA(-1) models were applied to Lambton county, Ontario, Canada to locate groundwater discharge areas for St. Clair River, calculate discharge rates, and hydrogeologic parameters. A sediment contamination model was developed and applied to Great Lakes sediment data to estimate transport parameters by Pb-210 data. It was then coupled with fatty acid data and results were compared with observed data. A contaminant transport model was developed and applied to two North American streams to compute stream water concentration. The computed data was compared with observed data using a simple statistical method. A hydrological model was coupled with water quality models and RAISON (regional analysis by intelligent systems on) expert system and applied to Canadian watersheds. Digital satellite data was used to locate groundwater discharge and recharge areas in the watershed. This data is useful as observed data for hydrological modelling and GIS (Geographical Information System) system. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 3. |
- Jonzén, Niclas, et al.
(författare)
-
Seasonal herbivory and mortality compensation in a swan-pondweed system.
- 2002
-
Ingår i: Ecological Modelling. - 0304-3800. ; 147:3, s. 209-219
-
Tidskriftsartikel (refereegranskat)abstract
- Many birds feed on submerged macrophytes during a temporally discrete period every year, for instance during migratory stopover or at the wintering grounds. Hence, seasonal herbivory is a common feature of the life cycle in many aquatic macrophytes. We are interested in the effect of Bewick's swans (Cygnus columbianus bewickii) feeding on the tubers of fennel pondweed (Potamogeton pectinatus) in the Netherlands every autumn. For that purpose, we developed a sequential macrophyte population model, including seasons of tuber production, herbivory and winter mortality as distinct and unambiguously defined events. The model is characterised and parameterised with both field and laboratory data. Tuber consumption inevitably decreases the density of ramets sprouting next spring, but it may actually increase the density of tubers produced in the following autumn. Hence, we can only understand the effect of grazing on the fennel pondweed population by recognising the seasonal structure of density-dependence. The mean density of fennel pondweed and the yield taken by swans are dependent on the foraging threshold below which no grazing takes place. Furthermore, the consumption has a stabilising effect for a wide range of parameter values.
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| 4. |
- Seaquist, Jonathan, et al.
(författare)
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A remote sensing-based primary production model for grassland biomes
- 2003
-
Ingår i: Ecological Modelling. - 0304-3800. ; 169:1, s. 131-155
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Forskningsöversikt (refereegranskat)abstract
- That data from polar orbiting satellites have detected a widespread increase in photosynthetic activity over the last 20 years in the grasslands of the Sahel is justifies investigating its role in the tropical carbon cycle. But this task is undermined because ground data that are generally used to support the use of primary production models elsewhere are lacking. In this paper, we profile a Light Use Efficiency (LUE) model of primary production parameterised with satellite information, and test it for the West African Sahel; solar radiation is absorbed by plants to provide energy for photosynthesis, while moisture shortfalls control the efficiency of light usage. In particular, we show how an economical use of existing, yet meagre data sets can be used to circumvent nominal, yet untenable approaches for achieving this for the region. Specifically, we use a cloudiness layer provided with the NOAA/NASA 8 km Pathfinder Land data archive (PAL) data set to derive solar radiation (and other energy balance terms) required to implement the model (monthly time-step). Of particular note, we index growth efficiency via transpiration by subsuming rangeland-yield formulations into our model. This is important for partially vegetated landscapes where the fate of rainfall is controlled by relative vegetation cover. We accomplish this by using PAL-derived Normalised Difference Vegetation Index (NDVI) to partition the landscape into fractional vegetation cover. A bare soil evaporation model that feeds into bucket model is then applied, thereafter deriving actual transpiration (quasi-daily time-step). We forgo a formal validation of the model due to problems of spatial scale and data limitations. Instead, we generate maps showing model robustness via Monte Carlo simulation. The precision of our Gross Primary Production (GPP) estimates is acceptable, but falls off rapidly for the northern fringes of the Sahel. We also map the locations where errors in the driving variables are mostly responsible for the bulk of uncertainty in predicted GPP, in this case the water stress factor and the NDVI. Comparisons with an independent model of primary production, CENTURY, are relatively poor, yet favourable comparisons are made with previous primary production estimates found for the region in the literature. A spatially exhaustive evaluation of our GPP map is carried out by regressing randomly sampled observations against integrated NDVI, a method traditionally used to quantify absolute amounts of primary production. Our model can be used to quantify stocks and flows of carbon in grasslands over the recent historical period. (C) 2003 Elsevier B.V. All rights reserved.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Kumblad, Linda, et al.
(författare)
-
An ecosystem model of the environmental transport and fate of carbon-14 in a bay of the Baltic Sea, Sweden
- 2003
-
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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| 8. |
- Repsilber, Dirk, 1971-, et al.
(författare)
-
Spatial genetic patterns systematically accelerate and bias drift-based genetic erosion
- 2002
-
Ingår i: Ecological Modelling. - Amsterdam, Netherlands : Elsevier. - 0304-3800 .- 1872-7026. ; 148:3, s. 251-261
-
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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| 9. |
- Westerberg, Lars, et al.
(författare)
-
Predicting the spatial distribution of a population in a heterogeneous landscape
- 2003
-
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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| 10. |
- Pommerening, Arne
(författare)
-
A new nearest-neighbour index for monitoring spatial size diversity: The hyperbolic tangent index
- 2020
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 435
-
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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| 11. |
- An, Li, et al.
(författare)
-
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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| 12. |
- An, Li, et al.
(författare)
-
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
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 471
-
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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| 13. |
- 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
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 471
-
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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| 14. |
- Bach, Lars, et al.
(författare)
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Kin competition and the evolution of dispersal in an individual-based model
- 2006
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 192:3-4, s. 658-666
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of dispersal was investigated in an adaptive individual-based metapopulation model, which allowed for demographic and environmental stochasticity. The individual dispersal behaviour was determined by a one-locus genotype subjected to simple inheritance and mutation. Dispersal behaviour could therefore evolve through the genotype–phenotype mapping and the selection regimes stemming from various ecological scenarios. Due to the individual-based design kin competition emerges per default rather than being approximated through an expected average level of relatedness. By decoupling reproduction and competition in the discrete life cycle dispersal was allowed to occur either before or after local competition. Hence, the degree to which dispersal relaxed competition among siblings was investigated directly with respect to the effect on the evolved dispersal rate. We found a pronounced difference in the evolved level of dispersal for certain combinations of local extinction and dispersal cost. However, when either of these two evolutionary forces (local fluctuation in fitness or dispersal cost) predominates, the effect of kin selection seems to be overshadowed. The island and the stepping stone structures gave somewhat similar patterns of adaptive response suggesting some robustness to spatial effects, although, as expected, the effect was less pronounced with nearest neighbour dispersal in the stepping stone model. The results demonstrate under different stochastic and spatial scenarios how the evolution of dispersal alleviates kin competition when it originates from the population renewal process as an emergent property. Moreover, predictions are suggested that may be addressed by selection experiments.
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| 15. |
- Baey, Charlotte, et al.
(författare)
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Calibration of a bumble bee foraging model using Approximate Bayesian Computation
- 2023
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 477
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Challenging calibration of complex models can be approached by using prior knowledge on the parameters. However, the natural choice of Bayesian inference can be computationally heavy when relying on Markov Chain Monte Carlo (MCMC) sampling. When the likelihood of the data is intractable, alternative Bayesian methods have been proposed. Approximate Bayesian Computation (ABC) only requires sampling from the data generative model, but may be problematic when the dimension of the data is high. 2. We studied alternative strategies to handle high dimensional data in ABC applied to the calibration of a spatially explicit foraging model for Bombus terrestris. The first step consisted in building a set of summary statistics carrying enough biological meaning, i.e. as much as the original data, and then applying ABC on this set. Two ABC strategies, the use of regression adjustment leading to the production of ABC posterior samples, and the use of machine learning approaches to approximate ABC posterior quantiles, were compared with respect to coverage of model estimates and true parameter values. The comparison was made on simulated data as well as on data from two field studies. 3. Results from simulated data showed that some model parameters were easier to calibrate than others. Approaches based on random forests in general performed better on simulated data. They also performed well on field data, even though the posterior predictive distribution exhibited a higher variance. Nonlinear regression adjustment performed better than linear ones, and the classical ABC rejection algorithm performed badly. 4. ABC is an interesting and appealing approach for the calibration of complex models in biology, such as spatially explicit foraging models. However, while ABC methods are easy to implement, they often require considerable tuning.
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| 16. |
- Banks, H. T., et al.
(författare)
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Modeling bumble bee population dynamics with delay differential equations
- 2017
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 351, s. 14-23
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Tidskriftsartikel (refereegranskat)abstract
- Bumble bees are ubiquitous creatures and crucial pollinators to a vast assortment of crops worldwide. Bumble bee populations have been decreasing in recent decades, with demise of flower resources and pesticide exposure being two of several suggested pressures causing declines. Many empirical investigations have been performed on bumble bees and their natural history is well documented, but the understanding of their population dynamics over time, causes for observed declines, and potential benefits of management actions is poor. To provide a tool for projecting and testing sensitivity of growth of populations under contrasting and combined pressures, we propose a delay differential equation model that describes multi-colony bumble bee population dynamics. We explain the usefulness of delay equations as a natural modeling formulation, particularly for bumble bee modeling. We then introduce a particular numerical method that approximates the solution of the delay model. Next, we provide simulations of seasonal population dynamics in the absence of pressures. We conclude by describing ways in which resource limitation, pesticide exposure and other pressures can be reflected in the model.
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| 17. |
- Bergkvist, John, et al.
(författare)
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Modelling managed forest ecosystems in Sweden : An evaluation from the stand to the regional scale
- 2023
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 477
-
Tidskriftsartikel (refereegranskat)abstract
- Incorporation of a forest management module in the dynamic vegetation model LPJ-GUESS has allowed the study and predictions of management treatment effects on the carbon cycle and on forest ecosystem structure. In this study, LPJ-GUESS is evaluated at the regional scale against observational data from the Swedish National Forest Inventory. Simulated standing volume is compared against observations for the four most common forest types in the country. Furthermore, eddy-covariance flux measurements from the Integrated Carbon Observation System (ICOS) are used to evaluate model predictions of net ecosystem exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (Reco) at the site scale. The model results suggest an adequate representation of standing volume in monocultures of Norway spruce and Scots pine for regional simulations in southern and central Sweden, after an updated parameterization of the species. For northern Sweden, the standing volume in Norway spruce monocultures was overestimated with the updated parameter values. At the stand scale, the model produced mixed results for carbon fluxes when evaluated against eddy-covariance data for two sites, one in central and one in southern Sweden. The interannual variation of GPP was well captured for the central Swedish site, but the modelled average GPP for the period 2015–2019 was overestimated by 9%. For the southern Swedish site, GPP was underestimated by 15% for the corresponding period and the simulated interannual variation was half of the observed. The seasonal estimates of modelled net ecosystem exchange (NEE) deviated from observations and the simulated standing volume was underestimated by 25% for both sites. The results highlight further potential to perform species-specific calibration to capture latitudinal gradients in key ecosystem properties, and to incorporate additional characteristics of site quality which could benefit model accuracy at the scale of individual forest stands, both regarding simulated carbon fluxes and forest stand variables.
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| 18. |
- Berglund, Moa, et al.
(författare)
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Optimal selection of marine protected areas based on connectivity and habitat quality
- 2012
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 240, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- Networks of nature reserves and protected areas are important instruments to protect biodiversity, including harvested populations. Selection of marine protected networks (MPA) will depend on both the connectivity of concerned species and the habitat quality of individual sites. We explore the relative effect of connectivity and habitat quality on solutions for optimal networks of MPA using eigenvalue perturbation theory and a metapopulation model. Based on analyses of both synthetic networks and realistic connectivities for a sessile invertebrate with planktonic larvae in the Baltic Sea, we show that connectivity is expected to be more efficient than habitat quality as a selection criterion for MPA networks with realistic probabilities of local recruitment. In a second series of analyses we explore the effect of temporal variability of connectivity on the selection of optimal MPA networks. We show that optimal solutions of MPA networks converged when based on 8-10 years of connectivity information, corresponding to the time scale of the North-Atlantic oscillation. In conclusion, this study indicates that connectivity may be more important than habitat quality as selection criterion for MPAs when targeting species with long-distance dispersal that is typical for many marine invertebrates and fish. Our study also shows that connectivity patterns may be relatively consistent in time which suggests that the recent progress in biophysical modelling can offer a framework for optimal selection of MPA networks based on connectivities, which should improve guidelines for the design of functional MPA networks.
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| 19. |
- 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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| 20. |
- Blennow, Kristina, et al.
(författare)
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Implementing storm damage in a dynamic vegetation model for regional applications in Sweden
- 2012
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 247, s. 71-82
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Tidskriftsartikel (refereegranskat)abstract
- Wind is the dominant agent of damage in forests in Western Europe. Traditional wind-damage models calculate a probability for damage or a critical wind speed at which damage occurs. However, in a dynamic vegetation model actual damage to stands and individual trees is needed to get a dynamical progression of the vegetation. We present a prototype for a new approach to modelling forest wind damage at the regional scale, which we incorporate within a dynamic vegetation model. The approach is based on knowledge from both empirical and mechanical models and calculates the damaged fraction of a cohort based on wind load and a sensitivity that depends on the current physical state and history of the cohort in relation to the ecosystem. The modelling concept has been developed, calibrated and evaluated for Swedish conditions but can be applicable to other similar areas with minor modification. Because of the stochastic nature of local wind load and the difficulty of describing the stand-level exposure, the ability to explain observed damage at stand level was low. Regional level variation in damage, which more depends on the wind load, was however explained reasonably well (R-2 = 0.43). We suggest that this is a useful concept for evaluating alternatives of forest management under different climate scenarios in the process of adaptation to future storm-damage risks. (C) 2012 Elsevier B.V. All rights reserved.
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| 21. |
- Bodin, Örjan, et al.
(författare)
-
Ranking individual habitat patches as connectivity providers : Integrating network analysis and patch removal experiments
- 2010
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 221:19, s. 2393-2405
-
Tidskriftsartikel (refereegranskat)abstract
- Here we propose an integrated framework for modeling connectivity that can help ecologists, conservation planners and managers to identify patches that, more than others, contribute to uphold species dispersal and other ecological flows in a landscape context. We elaborate, extend and partly integrate recent network-based approaches for modeling and supporting the management of fragmented landscapes. In doing so, experimental patch removal techniques and network analytical approaches are merged into one integrated modeling framework for assessing the role of individual patches as connectivity providers. In particular, we focus the analyses on the habitat availability metrics PC and IIC and on the network metric Betweenness Centrality. The combination and extension of these metrics jointly assess both the immediate connectivity impacts of the loss of a particular patch and the resulting increased vulnerability of the network to subsequent disruptions. In using the framework to analyze the connectivity of two real landscapes in Madagascar and Catalonia (NE Spain), we suggest a procedure that can be used to rank individual habitat patches and show that the combined metrics reveal relevant and non-redundant information valuable to assert and quantify distinctive connectivity aspects of any given patch in the landscape. Hence, we argue that the proposed framework could facilitate more ecologically informed decision-making in managing fragmented landscapes. Finally, we discuss and highlight some of the advantages, limitations and key differences between the considered metrics.
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| 22. |
- Bolinder, Martin, et al.
(författare)
-
Effects of climatic data low-pass filtering on the ICBM temperature- and moisture-based soil biological activity factors in a cool and humid climate
- 2011
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 222, s. 3050-3060
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Tidskriftsartikel (refereegranskat)abstract
- The air temperature (T-air), total precipitation (TP) and potential evapotranspiration (PET) are standard input data for soil carbon dynamic models, i.e., for calculating temperature and moisture effects on soil biological activity. The resolution needed depends on objectives, the complexity of models and inbuilt pedotransfer functions. The Introductory Carbon Balance Model (ICBM) soil climate front end model calculates a multiplicative soil-temperature (r(e_temp)) and -moisture (r(e_wat)) factor with a daily time-step to estimate soil biological activity, i.e., r(e_crop) = r(e_temp) x r(e_wat). Our objective was to determine how much re_temp. r(e_wat) and r(e_crop) are affected by low-pass filtering of the climatic input data for a cool, humid temperate region. To achieve this we conducted spectral analysis on T-air, TP, PET and r(e_crop) in the frequency domain. Thereafter we applied Fourier low-pass filters of 5, 15, 30, 60 and 180 days on T-air, TP, PET and tracked their effects through the soil climate model's state variables and outputs. This was done using a sandy and a heavy clay soil and an 89-year daily time-series from a meteorological station in Quebec (Canada). The Fourier spectra showed that the variance for T-air, PET and r(e_temp) was dominated by an annual cycle, as could be expected. There was no yearly cycle for TP. The variation in r(e_temp) explained most of the variance in r(e_crop). The soil climate module outputs were not sensitive to low-pass filtering of PET. A daily time-step was needed to avoid overestimating r(e_crop) for the sandy soil. Using a weekly time-step for TP and T-air allowed us to explain about 80% of the variance in r(e_crop) for the heavy clay soil. This study also indicates that the standard leaf (and green) area index functions for calculating transpiration should receive more attention, since they have significant effects on the state and output variables. (C) 2011 Elsevier B.V. All rights reserved.
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| 23. |
- Bommarco, Riccardo, et al.
(författare)
-
Outbreak suppression by predators depends on spatial distribution of prey
- 2007
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 201:2, s. 163-170
-
Tidskriftsartikel (refereegranskat)abstract
- The capacity of a predator population to suppress a prey population that varies in abundance and spatial distribution is explored in a lattice simulation model. The model is based on empirically derived parameters for particular species. Within season predation by Pterostichus cupreus (Coleoptera: Carabidae) of varying densities and distributions of the prey Rhopalosiphum padi (Homoptera: Aphididae) in spring cereals was simulated. From these spatially explicit simulations prey population suppression was found to be largely dependent on the spatial distribution of the prey. A possible mechanism was that high degrees of prey aggregation provided refuge for the prey that, when aggregated, escaped detection by P. cupreus. In contrast, P. cupreus was found to efficiently suppress incipient outbreaks for evenly distributed prey populations, even at high prey densities. A higher predator density compensated for the lowered control ability of the predators for highly aggregated prey populations and hastened the decline of the prey population.
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| 24. |
- Bras, Audrey
(författare)
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A temperature- and photoperiod-driven model reveals complex temporal population dynamics of the invasive box tree moth in Europe
- 2020
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 432
-
Tidskriftsartikel (refereegranskat)abstract
- The box tree moth, Cydalima perspectalis, is an invasive insect that has rapidly colonised Europe, damaging to natural and ornamental box trees. In its native habitat in China, the number of generations per year is variable, but the number of generations observed in European climates remained unclear. This is a key issue for understanding the rapid increase in population size and range, and for optimising control. We developed a temperature- and photoperiod-driven model to simulate the life cycle of this insect and development rates for each life stage. The model was calibrated on published data and validated with observations obtained in France and Switzerland. Model stability analysis showed that minimal temperature for larval development to be the most important parameter to estimate. Diapause parameters had little effect. We then explored the effects of temperature increases of 1 and 2 degrees C. The number of generations ranged from two to four at the various study sites. Climate warming will accelerate the insect life cycle, making it possible for the occurrence of one more generation per year. The key finding of this study was the complexity of population dynamics for this species. Some generations overlapped, making it difficult to identify the adult flight period clearly for each generation. Furthermore, various stages were potentially able to overwinter, not just diapausing larvae. Climate warming may also enhance this phenomenon in the future. Further explorations of the complex dynamics of this species are required, notably it remains unclear how successfully the various life stages survive winter temperatures. Further model refinements are also required to obtain more accurate estimates of box tree moth phenology. However, this is the first phenology model for box tree moth to be published, and our findings provide useful information for improving control of this pest.
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| 25. |
- Bryhn, Andreas Christoffer, 1971-, et al.
(författare)
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Predicting future effects from nutrient abatement and climate change on phosphorus concentrations in Lake Bourget, France
- 2010
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 221:10, s. 1440-1450
-
Tidskriftsartikel (refereegranskat)abstract
- Like many temperate European lakes, Lake Bourget (France) has suffered from eutrophication during the second half of the last century. Due to a remarkable policy restoration program, the lake has been recovering for the past 25 years after a massive decrease in total phosphorus (TP) loading. TP concentrations have decreased from about 100-120 to 20-25 µg/L. Additional efforts are, however, still required to obtain a perennially sustainable good ecological status and model parameterisation of fluxes can assist in predicting future outcomes, especially in the context of global warming. In this paper, a dynamic model (MeroLakeMab) was developed and tested with the purpose to reconstructthe loading history of Lake Bourget and to predict TP concentrations during scenarios of increased temperature, decreased water runoff and decreased P loading. Simulations suggested that the historical TP loading decrease may have been as extensive as 90%. Decreases in water discharge to Lake Bourget at magnitudes forecasted by the Intergovernmental Panel on Climate Change would not affect TP concentrations notably, but marked concentration changes could, however, occur if decreases in runoff would have a strong impact on the TP loading. Increasing temperature effects on yearly mean TP concentrations in the water column would be very small compared to effects from changes in the TP loading. Predictions such as these could be instrumental for future successful lake management.
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| 26. |
- Bryhn, Andreas, et al.
(författare)
-
Can nitrogen gas be deficient for nitrogen fixation in lakes?
- 2007
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 202:3-4, s. 362-372
-
Tidskriftsartikel (refereegranskat)abstract
- Severe nitrogen gas (N2) depletion in lakes may have implications for N2 fixation and for model structures describing the nitrogen (N) cycle. To determine whether this is likely to occur, we first reviewed the general processes influencing the N2 cycle in lakes. Second, we empirically analysed N2 concentrations in various stations and depths of Lake Erken, Sweden during the beginning and the end of the summer stratification period of 2004. Overall, no significant deviations from N2 saturation from any stations or depths were observed during the study period. Third, we developed a simple, one-box gas model to investigate possible effects on lake water from processes described in the literature that affect the N2 concentration. Simulations indicated that bottom waters and other isolated water bodies may show strong deviations from N2 saturation during certain conditions differing from those during summers in Lake Erken. Simulated surface waters were always N2 saturated in all types of lakes where the water column was in direct contact with the air. We quantified all probable fluxes, showed that the N2 concentration in surface waters vastly exceeds the half-saturation constant for N uptake by phytoplankton, and concluded that it is unlikely that N2 fixation is ever limited by the N2 concentration. Modellers of lake eutrophication may regard N2 as being available in excess.
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| 27. |
- Bryhn, Andreas, et al.
(författare)
-
Modelling the biomass of functional groups of fish in an archipelago bay of the Baltic Sea
- 2013
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 269, s. 86-97
-
Tidskriftsartikel (refereegranskat)abstract
- Fish biomass estimates in European coastal waters are necessary for several reasons, e.g., for meeting requirements in legislation and international agreements, for establishing sustainable outtakes of the resources, for developing management plans and for assessing the ecological and environmental status of coastal waters. This study estimated piscivorous and non-piscivorous fish biomass as well as total fish biomass in Kvadofjarden Bay on the Swedish Baltic Sea coast using dynamic foodweb modelling. Weight-per-unit-effort data from the coastal fish monitoring program in the area together with a range of abiotic variables (including salinity and total phosphorus) were used as drivers for the CoastWeb model. To further refine the estimates of fish biomass, we complemented the model by using data from nearby areas on the ratio of piscivorous to non-piscivorous fish for those size classes not representatively sampled by the monitoring gear (fish < 12 cm). Piscivorous fish biomass in the area was estimated at 10-14 tonnes (4.6-6.5 kg/ha), non-piscivorous fish biomass at 105-139 tonnes (47-62 kg/ha) and the subsequent total fish biomass was estimated at 115-154 tonnes (52-69 kg/ha). The estimated range of total fish biomass was comparable with findings from other investigations on the Swedish Baltic Sea coast which used a coarser methodology. The method presented in this paper can be used for making biomass estimates in other coastal waters where passive gears are used to monitor the local fish communities, and could thus serve a range of purposes for assessing the production and status of fish in coastal waters. (C) 2013 Elsevier B.V. All rights reserved.
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| 28. |
- Bundschuh, Mirco
(författare)
-
Modeling cumulative effects of acute exposure to toxicants on the life cycle of Chironomidae using Bti as a case study
- 2024
-
Ingår i: Ecological Modelling. - 0304-3800 .- 1872-7026. ; 494
-
Tidskriftsartikel (refereegranskat)abstract
- Chironomidae are the most abundant aquatic insect group and are important in providing energy and nutrients to aquatic and terrestrial food webs. The stress response of Chironomidae can vary with environmental conditions and time of pollutant exposure, making it difficult to understand the underlying mechanisms. Here, we use a dynamic population model to predict the potential effects of anthropogenic stressors on Chironomus riparius larvae and adult emergence for up to two years. We employed the non -chemical larvicide Bacillus thuringiensis var. israelensis (Bti) as a case study, as this stressor has been shown to reduce larval survival of C. riparius. To predict the responses of C. riparius adapted to variable geographic conditions, we simulated scenarios in which Bti is applied at three different latitudes in Europe. For each latitude, we also simulated a varying Bti application timing corresponding to a higher or a lower density of early-instar larvae, for which a higher sensitivity to Bti is documented. While acute exposure to Bti did not alter the patterns of larval development and adult emergence, in all scenarios and latitudes considered, the predicted reduction was stronger when Bti was applied to populations with a prevalence of early-instar larvae. Moreover, in all simulated scenarios, the reduction in the second year of Bti application was approximately twice as large as in the first year, revealing cumulative effects. Our model can be used to develop new hypotheses and test them through either empirical or in silico experiments to project the long -term effects of Bti on Chironomidae populations. The model can be theoretically applied to other insect groups and toxicants, and to different latitudinal scenarios by changing input parameters.
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| 29. |
- Carlman, Inga, et al.
(författare)
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Models and methods as support for sustainable decision-making with focus on legal operationalisation
- 2015
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 306, s. 95-100
-
Tidskriftsartikel (refereegranskat)abstract
- Since the 1960s the urgency to steer mankind towards a more sound environment has grown. Currently humanity is in a transition period between today’s old paradigm – business as usual – and the new one, aiming at operationalise sustainable development goals. There is a growing understanding, that to move towards sustainable development, ecological sustainability is necessary but not sufficient. Steering society in this direction necessitates making decisions that at least do not counteract sustainability.Such decisions have to rest firmly on a natural scientific basis. Natural laws, such as thermodynamics, and conditions set by ecosystems can therefore not been ignored, when (a) searching for technical solutions to environmental problems and to fully understand the consequences of such solutions, and (b) improving steering instruments to guide human actions.Over the years a number of models/methods/systems have been developed to underpin sustainable decision-making, such as Environmental Impact Assessment (EIA), Life Cycle Assessment (LCA), Ecological Footprints, and Cost Benefit Analysis (CBA). Ecological modelling contributes or complements such methods. Emergy analysis, an environmental accounting and assessment method takes a wider grip embracing both ecology and economy. Less known is environmental legal modelling.This paper puts ecological models in the context of societal steering systems for sustainable development, and focuses on a legal model for implementing environmental policy goals.
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| 30. |
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| 31. |
- Chapron, Guillaume, et al.
(författare)
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Estimating wolf (Canis lupus) population size from number of packs and an individual based model
- 2016
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 339, s. 33-44
-
Tidskriftsartikel (refereegranskat)abstract
- Estimating wildlife population-size is fundamental for wildlife management and conservation. However, making monitoring of population size less resource demanding while still keeping a high monitoring accuracy and precision remains a recurrent challenge. One proposed alternative to count individuals is to instead focus on counting a segment of the population that is easier to monitor but at the same time well informative on total population size. We show how total population size can be estimated from group counts by using an individual-based population model in a social living species. We developed a wolf (Canis lupus) specific Individual Based Model and used Approximate Bayesian Computation (ABC) to fit this population model to the time series of annual number of packs, reproductions and pairs obtained from Scandinavian monitoring data. Model informative priors were obtained with data from collared individuals by the Scandinavian wolf research project. The fitted model was then used to estimate a conversion factor from number of packs to total number of individuals and to number of reproductions. There was a good fit between the retained simulations by ABC and the observed Scandinavian wolf population trajectory. The fitted simulations returned a conversion factor of 8.0 (95% CI = 6.62-10.07) from number of packs to total population size and of 1.0 (95% CI = 0.93-1.12) to number of reproductions in December. A sensitivity analysis revealed that the conversion factor from packs to total population size was positively correlated with pup survival and litter size and negatively correlated with subadult, vagrant and adult survivals. Using an individual based model allowed us to model the full complexity of demographic traits of a social-living species such as the wolf. The flexibility of the model also meant that the conversion factor could be estimated for any month during the year. Our approach to estimate total population size from counts of groups requires having a population model where both individuals and groups are explicitly described and can be applied to other wolf populations and group-living species where counting all individuals over a large area is unfeasible.
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| 32. |
- Chapron, Guillaume
(författare)
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Reducing matrix population models with application to social animal species
- 2012
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 232, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- Stage-structured matrix models are commonly used to inform management decisions for species with complex life cycles. These models require information on the number or proportion of individuals in each stage. However, complex life cycles, such as those in species exhibiting a complex social organization, can make these data difficult to obtain. The discrete time structure of matrix models makes them reducible, meaning that full models can be simplified by removing some stages. We illustrate the method by reducing the life cycle of wolf (Canis lupus) on which culling and conservation plans often lead to controversial debates. Starting from a 4-stage matrix incorporating social stages, we obtained several reduced models of increasing simplicity all showing similar demographic outcomes to the full model. We found that asymptotic growth rates of reduced models were in close agreement with empirical data. Our approach can offset the lack of information on individual stage abundance and therefore be valuable when using matrix models for wildlife management when data on certain stages are sparse. (C) 2012 Elsevier B.V. All rights reserved.
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| 33. |
- Claesson, Jonas, et al.
(författare)
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Combined effect of global warming and increased CO2-concentration on vegetation growth in water-limited conditions
- 2013
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 256, s. 23-30
-
Tidskriftsartikel (refereegranskat)abstract
- The most severe impact of climate change on vegetation growth and agriculture is likely to occur under water-limited conditions. Under such conditions the plants optimize the inward flux of CO2 and the outward flux of water vapor (the transpiration) by regulating the size of the stomatal openings. Higher temperature increases water loss through transpiration, forcing the plants to diminish the stomatal openings, which decreases photosynthesis. This is counteracted by higher CO2 concentration, which allows plants to maintain the inward flux of CO2 through the smaller openings. These two counteracting effects, combined with the change in precipitation, determine the net change of biological productivity. Here, a vegetation sensitivity approximation (VSA) is introduced, in order to understand and estimate the combined effect of changed temperature, CO2 and precipitation to first order. The VSA is based on the physical laws of gas flux through the stomatal openings, and is only valid under water-limited conditions. It assumes that the temperature depends logarithmically on the CO2 concentration with a given climate sensitivity. Precipitation is included by assuming that it is proportional to the transpiration. This is reasonable underwater-limited conditions, when transpiration is often a large fraction of the precipitation. The VSA is compared to simulations with the dynamic vegetation model LPJ. The agreement is reasonable, and the deviations can be understood by comparison with Koppen's definition of arid climate: in an arid climate growth increases more according to LPJ than according to the VSA, and in non-arid conditions the reverse is true. Both the VSA and the LPJ simulations generally show increased growth with increasing CO2 levels and the resulting temperature increase, assuming precipitation to be unchanged. Thus, in this case the negative temperature effect is more than compensated by the positive effect of CO2.
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| 34. |
- Elhabashy, Ahmed, et al.
(författare)
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Water quality modeling of a eutrophic drinking water source: Impact of future climate on Cyanobacterial blooms
- 2023
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 477
-
Tidskriftsartikel (refereegranskat)abstract
- Cyanobacterial blooms are becoming more frequent in freshwater sources, causing concern throughout the world. Cyanobacterial blooms affect human health and the entire environment. Numerical modeling is an effective tool for investigating aquatic systems. In this study, a 3D hydrodynamic and water quality (ecological) model was used to simulate eutrophication of a drinking water source, Lake Vomb, in Sweden under present and future scenarios. The hydrodynamic model was set-up in MIKE 3 FM software based on meteorological, hydrological, and water quality data. The hydrodynamic model performance was satisfactory in terms of the water temperature simulation, with root-mean-square-error (RMSE) ranging from 0.38 to 1.2 °C. In the ecological model, Chlorophyll-a (Chl-a) was used as a proxy for Cyanobacteria, and the model proved acceptable in simulating the Chl-a concentrations, with a Nash-Sutcliffe efficiency (NSE) of 0.93 and 0.87 for calibration and validation respectively. The findings revealed that external nitrogen loading and internal phosphorus loading had significant impact on the nutrient concentrations in Lake Vomb. The findings also showed a correlation between Chl-a levels and total phosphorus levels in the lake. To simulate future water quality in the lake, two Representative Concentration Pathways (RCP) for the year 2050 were used to make projections for changes in air temperature and precipitation. Under the projected future climate, the simulations showed a considerable rise in Cyanobacteria biomass independent of the changes in external nutrient loading. The model findings can assist water managers in planning mitigation strategies by identifying major nutrient sources.
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| 35. |
- Elliott, J.A., et al.
(författare)
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Phytoplankton modelling of Lake Erken, Sweden by linking the models PROBE and PROTECH
- 2007
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 202:3-4, s. 421-426
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Tidskriftsartikel (refereegranskat)abstract
- A phytoplankton community model (PROTECH) and a lake physical model (PROBE) were linked, for the first time, to simulate the phytoplankton community of Lake Erken (Sweden). This allowed the physical effects of ice formation to be incorporated into the calculations of PROTECH. This is the highest latitude lake simulated by PROTECH thus far and was a further test of its biological application to lake ecosystems in general. A new cyanobacteria species was added to the PROTECH model: Gloeotrichia echinulata (Smith) Richter which had functional characteristics never before simulated in PROTECH and was an order of magnitude larger than species previously simulated. The biological outputs of total chlorophyll a were successfully validated against quantitative observations from the lake (EF = 0.76). The addition of G. echinulata to the model notably improved this fit, particularly in the period from July to October. Key taxa biomass were also simulated, with good fits for diatoms (EF = 0.70) and cyanobacteria (EF = 0.83). Furthermore, the characteristic periodic blooms of Gloeotrichia were captured, thus supporting its assigned model parameters and suggesting that PROTECH's growth equations can be applied to this significantly larger species. Furthermore, it appears that Gloeotrichia's simulated seasonal pattern of growth was greatly dependent upon the water temperature.
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| 36. |
- Erlandsson Lampa, Martin, et al.
(författare)
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Effects of whole-tree harvesting on soil, soil water and tree growth - A dynamic modelling exercise in four long-term experiments
- 2019
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 414
-
Tidskriftsartikel (refereegranskat)abstract
- Whole tree harvesting (WTH) following final felling of productive forests is increasingly promoted as a method to extract biomass for energy purposes. Despite its importance, there is a limited number of experimental studies investigating the impacts of WTH on forest ecosystem sustainability. Modelling studies have previously been carried out to complement and explain empirical observations from four long-term WTH experiments in Sweden. The literature shows a significant discrepancy between these studies, and open questions remain as to the fate of the base cations that are not removed in the absence of WTH. This study uses the integrated ecosystem model ForSAFE, which simulate a forest ecosystem's biogeochemical processes and the feedbacks between these processes, to trace the fate of base cations for the said four long-term WTH experiments. The study shows that the model generally captures the observed effects of WTH on the stocks of base cations in the biomass and in the soil. The modelled results were also used to map how the base cations removed through WTH would otherwise (if left at the site) have been distributed in the ecosystem. The results indicate that the soil organic pool may be more important to the long-term base cation balance than the exchangeable pool, and should receive more attention in future research.
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| 37. |
- Evans, Luke C., et al.
(författare)
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Quantifying the effectiveness of agri-environment schemes for a grassland butterfly using individual-based models
- 2019
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 411
-
Tidskriftsartikel (refereegranskat)abstract
- The intensification of agricultural practices throughout the twentieth century has had large detrimental effects on biodiversity and these are likely to increase as the human population rises, with consequent pressure on land. To offset these negative impacts, agri-environment schemes have been widely implemented, offering financial incentives for land-owners to create or maintain favourable habitats that enhance or maintain biodiversity. While some evidence is available on the resulting species richness and abundance for groups such as natural predators, pollinating insects including butterflies and moths, this is costly to obtain and it is difficult to predict the effects of specific habitat designs. To alleviate this problem we here develop an individual-based model (IBM), modelling the detailed movement behaviour, foraging, and energy budget of a grassland butterfly Maniola jurtina Linn. in patches of varying dimensions and quality. The IBM is successfully validated against data on M. jurtina densities, movement behaviour, resource use, fecundity and lifespan in habitats of varying quality. We use the IBM to quantify the benefits for life-history outcomes of M. jurtina of increasing the quantity and the quality of field margins within agricultural landscapes. We find that increasing the quantity of field margin habitat from 1 to 3 ha per 100 ha, as recommended in agri-environment schemes, increases the average number of eggs laid across a two-week period by 60% and adds an extra day to the average lifespan. Similar effects are reported for variation in the quality of field margins. We discuss the implications of the result for modelling butterfly responses to management scenarios.
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| 38. |
- Farahbakhshazad, Neda
(författare)
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Modeling nitrate leaching with a biogeochemical model modified based on observations in a row-crop field in Iowa
- 2006
-
Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 196:1-2, s. 116-130
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Tidskriftsartikel (refereegranskat)abstract
- Prediction of nitrate leaching from cropland is crucial for preventing surface or ground water degradation. Accurate modeling of nitrate leaching requires simulations of both soil hydrological and biogeochemical processes. This paper reports an attempt to improve an existing biogeochemical model, Denitrification-Decomposition or DNDC, for estimation of nitrate leaching from crop fields with tile drainage system. DNDC was equipped with detailed biogeochemical processes of nitrogen turnover but a simple module for one-dimensional movement of soil water. Observations from nine drainage tiles with three different fertilizer treatments in 4 years (1996-1999) at an experimental field in Iowa were used for model modifications. Preliminary comparisons with observed tile discharge flow indicated that the original DNDC lacked the water leaching recession character. To correct this deviation, new water retention features were added to DNDC by: (1) adopting a recession curve to regulate the gravity drainage flow in the explicitly simulated soil profile (0-50 cm) and (2) introducing a virtual water pool for the space between the bottom of the modeled soil profile (50 cm) and the tile lines depth of placement (145 cm) to control the tile discharge flow. With these modifications, model prediction of water leaching fluxes from the tile drainage lines was improved. An adsorbed N pool was created in DNDC to simulate the buffering effect of soil on the amount of nitrate available for leaching. The Langmuir equation was adopted to simulate adsorption and desorption of ammonium ions on the soil absorbents. This modification enhanced the model capacity for simulating free ammonium dynamics, nitrification, and nitrate leaching. Sensitivity tests of the modified DNDC showed that the modeled impact of differences of precipitation, soil texture, soil organic carbon content, and fertilizer application rates on nitrate leaching rates were consistent with observations reported by other researchers. This study indicated that a biogeochemical model with limited modifications in hydrology could serve nitrate leaching prediction and be useful for sustainable agricultural management.
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| 39. |
- Gaudio, Noemie, et al.
(författare)
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Combined effect of atmospheric nitrogen deposition and climate change on temperate forest soil biogeochemistry: A modeling approach
- 2015
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 306, s. 24-34
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric N deposition is known to severely impact forest ecosystem functioning by influencing soil biogeochemistry and nutrient balance, and consequently tree growth and overall forest health and biodiversity. Moreover, because climate greatly influences soil processes, climate change and atmospheric N deposition must both be taken into account when analysing the evolution of forest ecosystem status over time. Dynamic biogeochemical models have been developed to test different climate and atmospheric N deposition scenarios and their potential interactions in the long term. In this study, the ForSAFE model was used to predict the combined effect of atmospheric N deposition and climate change on two temperate forest ecosystems in France dominated by oak and spruce, and more precisely on forest soil biogeochemistry, from today to 2100. After a calibration step and following a careful statistical validation process, two atmospheric N deposition scenarios were tested: the current legislation in Europe (CLE) and the maximum feasible reduction (MFR) scenarios. They were combined with three climate scenarios: current climate scenario, worst-case climate scenario (A2) and best-case climate scenario (B1). The changes in base saturation and inorganic N concentration in the soil solution were compared across all scenario combinations, with the aim of forecasting the state of acidification, eutrophication and forest ecosystem recovery up to the year 2100. Simulations highlighted that climate had a stronger impact on soil base saturation, whereas atmospheric deposition had a comparative effect or a higher effect than climate on N concentration in the soil solution. Although deposition remains the main factor determining the evolution of N concentration in soil solution, increased temperature had a significant effect. Results also highlighted the necessity of considering the joint effect of both climate and atmospheric N deposition on soil biogeochemistry.
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| 40. |
- Grabarnik, Pavel, et al.
(författare)
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Modelling the spatial structure of forest stands by multivariate point processes with hierarchical interactions
- 2009
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Ingår i: Ecological Modelling. - 0304-3800. ; 220, s. 1232-1240
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Tidskriftsartikel (refereegranskat)abstract
- A stochastic model is applied to describe the spatial structure of a forest stand. We aim at quantifying the strength of the competition process between the trees in terms of interaction within and between different size classes of trees using multivariate Gibbs point processes with hierarchical interactions introduced by Högmander and Särkkä (1999). The new model overcomes the main limitation of the traditional use of the Gibbs models allowing to describe systems with non-symmetric interactions between different objects. When analyzing interactions between neighbouring trees it is natural to assume that the size of a tree determines its hierarchical level: the largest trees are not influenced by any other trees than the trees in the same size class, while trees in the other size classes are influenced by the other trees in the same class as well as by all larger trees. In this paper, we describe a wide range of Gibbs models with both hierarchical and non-hierarchical interactions as well as a simulation algorithm and a parameter estimation procedure for the hierarchical models. We apply the hierarchical interaction model to the analysis of forest data consisting of locations and diameters of tree stems.
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| 41. |
- Grandin, Ulf
(författare)
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Assessment of ecosystem integrity and service gradients across Europe using the LTER Europe network
- 2015
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 295, s. 75-87
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Tidskriftsartikel (refereegranskat)abstract
- Better integration of knowledge from ecological, social and economic science is necessary to advance the understanding and modelling of socio-ecological systems. To model ecosystem integrity (El) and ecosystem services (ES) at the landscape scale, assessment matrices are commonly used. These matrices assign capacities to provide different services to different land cover types. We revised such an existing matrix and examined the regional heterogeneity in El and ES provision in Europe and searched for spatial gradients in their provision to elucidate their suitability for large-scale El and ES mapping in Europe. Overall, 28 sites belonging to the Long-Term Ecological Research network in Europe participated in this study, covering a longitudinal gradient from Spain to Bulgaria and a latitudinal gradient from Italy to Sweden. As a primary outcome, an improved and consolidated El and ES matrix was achieved with 17.5% of all matrix fields updated. For the first time, this new matrix also contains measures of uncertainty for each entry. El and ES provision assessments were more variable for natural and semi-natural than for more anthropogenically dominated land cover classes. Among the main types of El and ES, cultural service provision was rated most heterogeneously in Europe, while abiotic provisioning services were more constant. Longitudinal and latitudinal El and ES gradients were mostly detected in natural and semi-natural land cover types where temperature and precipitation are major drivers. In anthropogenically determined systems in which cultural services play a dominant role, temperature and precipitation gradients were less important. Our results suggest that this matrix approach to assess El and ES provision principally works on broad spatial scales; however, local assessments for natural systems seem to be less generalizable than assessments from anthropogenically determined systems. Provisioning and regulating services are more generalizable than cultural services. Particularly in natural and semi-natural systems, spatial gradients need to be considered. We discuss uncertainties associated with this matrix-based El and ES assessment approach and suggest that future large-scale studies should include additional land cover information and ecosystem disservices and may determine ES fluxes by differentiating between ES provision and consumption. (C) 2014 Elsevier B.V. All rights reserved.
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| 42. |
- Granvik, Madeleine
(författare)
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Assessing, valuing and mapping ecosystem services at city level: The case of Uppsala (Sweden)
- 2018
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 368, s. 411-424
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Tidskriftsartikel (refereegranskat)abstract
- Urbanization is an important driver of environmental changes causing an increasing demand of ecosystem services while altering natural ecosystems. Yet, the sustainable management of urban areas can support the long-term provision of goods and services typical of healthy and resilient ecosystems and essential for human well-being. In this study, multiple ecosystem services generated by forest, agricultural (cropland and grassland), and urban areas in the municipality of Uppsala (Sweden) were first assessed in biophysical terms and then valued in money units. Afterwards, the economic value of provisioning and regulating services was spatialized using Geographic Information Systems (GIS). The economic value of all investigated services amounted to 1.81 billion Swedish Kronor (SEK) or 198 million (sic) per year, of which: 80% generated by forest areas, 19% by agricultural areas, and 1% by green urban areas. Considering the size of different land uses, the average economic value of green urban areas was the highest (20,000 SEK ha(-1) or 2200 (sic) ha(-1)), followed by forest areas (11,387 SEK ha(-1) or 1250 (sic) ha(-1)), and agricultural areas (6398 SEK ha(-1) or 703 (sic) ha(-1)). The integration between the assessment of the biophysical and economic value of several ecosystem services provided by different land uses as well as their spatial analysis allowed a deeper understanding on the ecological life-support system to the urban area of Uppsala. In conclusion, we maintain that the interplay between nature services and human settlements can be better explored by using an interdisciplinary approach providing ecological and economic information integrated in support of policy makers and urban planners. (C) 2017 Elsevier B.V. All rights reserved.
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| 43. |
- Grelle, Achim
(författare)
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Vegetation-specific model parameters are not required for estimating gross primary production
- 2014
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 292, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Models of gross primary production (GPP) based on remote sensing measurements are currently parameterized with vegetation-specific parameter sets and therefore require accurate information on the distribution of vegetation to drive them. Can this parameterization scheme be replaced with a vegetation-invariant set of parameters that can maintain or increase model applicability by reducing errors introduced from the uncertainty of land cover classification? Based on the measurements of ecosystem carbon fluxes from 168 globally distributed sites in a range of vegetation types, we examined the predictive capacity of seven light use efficiency (LUE) models. Two model experiments were conducted: (i) a constant set of parameters for various vegetation types and (ii) vegetation-specific parameters. The results showed no significant differences in model performance in simulating GPP while using both set of parameters. These results indicate that a universal of set of parameters, which is independent of vegetation cover type and characteristics can be adopted in prevalent LUE models. Availability of this well tested and universal set of parameters would help to improve the accuracy and applicability of LUE models in various biomes and geographic regions. (C) 2014 Elsevier B.V. All rights reserved.
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| 44. |
- Grönlund, Erik, 1964-, et al.
(författare)
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Donor values in emergy assessment of ecosystem services
- 2015
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 306, s. 101-105
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Tidskriftsartikel (refereegranskat)abstract
- There are currently many definitions of ecosystem services in use. Common for them is an aim to visualize contributions, assets and costs not traditionally covered by market valuations, thus often giving the ecosystems much lower value than their importance to economy. Emergy accounting, with its approach of donor values in contrast to receiver or market values, is one approach to assess contributions from the ecosystems and increase our understanding of the values of ecosystem services.Other authors have connected the donor-side approach with a user side approach for ecological services. In this paper, we investigate the donor-side more in depth, and put up an emergy model with two possible main paths to assess the values for the ecosystem services: (1) the emergy values of the natural driving forces (DrivEES), such as sun, rain, wind and land cycle and (2) the emergy values delivered directly to the human society and economy (FuncESS, ecosystem function ecosystem services). The first approach can be assessed with the common calculation procedure of emergy accounting; the second includes more challenging feedback flows of different types. The implications of these different feedback flows are discussed in this paper. The Millennium Ecosystem Assessment terminology of supporting, providing, regulating and cultural ecosystem services relate primarily to the emergy FuncESS flows.
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| 45. |
- Hakanson, L
(författare)
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A general method to define confidence limits for model predictions based on validations
- 1996
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Ingår i: ECOLOGICAL MODELLING. - : ELSEVIER SCIENCE BV. - 0304-3800. ; 91:1-3, s. 153-168
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An algorithm has been derived to calculate 95% confidence limits for values predicted by, e.g., ecosystem models. The approach uses a validation procedure involving: regression of values predicted by the model against independent empirical data, not uncer
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| 46. |
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| 47. |
- Hakanson, L, et al.
(författare)
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A practical approach to predict the duration of the growing season for European lakes
- 2001
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Ingår i: ECOLOGICAL MODELLING. - : ELSEVIER SCIENCE BV. - 0304-3800. ; 140:3, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the first practically useful models to estimate the duration of the growing season (CS in days) for European lakes. GS is a fundamental parameter in limnology, where it is used, e.g., to calculate lake characteristic annual primary prod
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| 48. |
- Hakanson, L
(författare)
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A simple model to predict the duration of the mercury problem in Sweden
- 1996
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Ingår i: ECOLOGICAL MODELLING. - : ELSEVIER SCIENCE BV. - 0304-3800. ; 93:1-3, s. 251-262
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- There are about 83 000 lakes in Sweden; about 40 000 lakes have fish (here = 1 kg pike) with Hg-concentrations above the guideline of 0.5 mg Hg/kg ww; about 10 000 lakes have pike with Hg-concentrations higher than the 'blacklisting' limit of 1.0 mg Hg/kg
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| 49. |
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| 50. |
- HAKANSON, L
(författare)
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MODELS TO PREDICT ORGANIC CONTENT OF LAKE-SEDIMENTS
- 1995
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Ingår i: ECOLOGICAL MODELLING. - : ELSEVIER SCIENCE BV. - 0304-3800. ; 82:3, s. 233-245
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study is to quantify and rank variables of significance to predict mean organic content (IG, loss on ignition) of surficial (0-1 cm) lake sediments in small glacial lakes. Various hypotheses concerning the factors regulating IG in lakes we
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