Optimal size of predictive models

Håkanson, Lars

doi:10.1016/0304-3800(93)e0103-a

Cited by 70 publications

(37 citation statements)

References 5 publications

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“…Optimisation theory has been used mainly for modelling resource or ecosystem management (e.g. Van der Molen and Pintér, 1993;Straškraba, 1994;Håkanson, 1995;Tiwari et al, 1996;Williams, 1996). Our paper illustrates how optimisation theory can be used for the analysis of plasticity in shoot morphology of plants in response to environmental changes, as well as the analysis of diversity in morphology.…”

Section: Discussionmentioning

confidence: 98%

The effect of population density on shoot morphology of herbs in relation to light capture by leaves

Sekimura

Koebernick

Лі

et al. 2000

Ecological Modelling

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Plants change their shapes, depending on their environment, for example, plant height increases with increasing population density. We examined the density-dependent plasticity in shoot morphology of herbs by analysing a mathematical model which identifies a number of key factors that influence shoot morphology, namely (i) solar radiation captured by leaves; (ii) shading from neighbouring plants; and (iii) utilisation efficiency of resource by leaves, stems and veins. An optimisation theory was used to obtain optimal shoot morphology in relation to maximal light capture by leaves, under trade-offs of resource partition among organs. We first evaluated the solar radiation flux per unit leaf area per day for different shoot forms. Our model predicts that the optimal internodal length of the stem that brings about the maximal light capture by leaves increases with plant population density, and this is consistent with experimental data. Moreover, our simple model can also be extended to explain the morphological plasticity in other herbs (i.e. stemless plants) that are different from our model plants with a stem. These findings illustrate how optimisation theory can be used for the analysis of plasticity in shoot morphology of plants in response to environmental changes, as well as the analysis of diversity in morphology.

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Section: Discussionmentioning

confidence: 98%

The effect of population density on shoot morphology of herbs in relation to light capture by leaves

Sekimura

Koebernick

Лі

et al. 2000

Ecological Modelling

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“…The findings of Håkanson (1995) and those of Costanza & Sklar (1985) provide evidence for the long-held belief that predictive power increases quickly with the elaboration of simple models, but the trend is eventually reversed as accumulating errors and process and parameter uncertainty negate any potential benefits of increased detail (Jester et al 1977). Håkanson (1997) provided an additional explanation for the decline in performance with increased detail.…”

Section: Construction Rulesmentioning

confidence: 89%

“…Studies of the effect of model structure that have already taken place indicate that there is a humped form to the relationship between model detail and performance (Costanza & Sklar 1985, Håkanson 1995, Fulton 2001. Too much complexity leads to too much uncertainty and problems with interpretation of the model's dynamics and predictions, while too little detail results in models that cannot produce realistic behaviours.…”

Section: Discussionmentioning

confidence: 99%

“…Botkin 1977), and the conclusions from Håkan-son's (1995) work on predictive multispecies models for lakes and coastal areas. Håkanson (1995) tried to compare empirical and dynamic models by first considering the r 2 values of a number of stepwise multiple-regression models and then by examining the standard deviation of a number of additive and multiplicative models. Once again it was shown that there was a humped relationship between an indicator of performance and the number of variables included, although in this case the peak of the plot was closer to the smaller model sizes (Fig.…”

Section: Construction Rulesmentioning

confidence: 99%

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Effect of complexity on marine ecosystem models

Fulton¹,

Smith²,

Johnson³

2003

Mar. Ecol. Prog. Ser.

272

171

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Ecosystem rather than species management has become an explicit part of policies that feature in international treaties and national legislation. Many of the tools that will be needed to fulfil the requirements of these policies are still in an early stage of development. One such tool is trophic ecosystem modelling. These models have been put forward to aid system-level understanding and provide insight into the potential impacts of human activities. Despite this, there are many gaps in knowledge of their strengths and weaknesses. In particular, little is known about the effect of the level of detail in a model on its performance. There has been some consideration of the effects of model formulation, as well as the effects of the physical, biological and chemical scope of multispecies and ecosystem models on their performance. A review of existing research indicates that there is a humped relationship between model detail and performance for these models, and that there are some guiding principles to consider during model development. This review gives some insight into which model structures and assumptions are likely to aid understanding and management, and which may be unnecessary. Further, it provides some understanding of whether some models can capture properties of real systems that other models cannot. The main recommendation is that the use of a single 'ultimate' ecosystem model is ill-advised, while the comparative and confirmatory use of multiple 'minimum-realistic' models is strongly recommended.

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“…They are driven by readily accessible environmental parameters from European databases and GIS-systems. The models are often based on "collective parameters" (Monte, 1996;Håkanson, 1995). The values of such parameters integrate many compensatory effects occurring in the very complex ecosystem where "everything depends on everything else" (Håkanson and Peters, 1995).…”

Section: The Moira-plus Models For Predicting the Environmental Behavmentioning

confidence: 99%

MOIRA-PLUS: A decision support system for the management of complex fresh water ecosystems contaminated by radionuclides and heavy metals

Monte

Brittain

Gallego

et al. 2009

Computers & Geosciences

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Abstract. The accidental release of radioactive substances into the environment leads to the necessity of applying suitable countermeasures for the restoration of the polluted environment. However, despite their obvious benefits, such interventions may result in detrimental effects of economic, ecological and social nature that must be carefully evaluated.MOIRA-PLUS is a PC-based user-friendly, Computerised Decision Support System (CDSS) that helps decision makers to choose optimal countermeasure strategies for different kinds of aquatic ecosystems and contamination scenarios.CDSS MOIRA-PLUS is based on: a) Validated models to evaluate the behaviour of radionuclides in contaminated water bodies and biota and to assess the effect of countermeasures on the contamination levels; b) Models to assess the radiation dose to people and biota (fish) by the relevant exposure pathways, the effect of countermeasures, and the associated economic impact; c) Multi-Attribute value Analysis (MAA) module to assess the effectiveness of different management strategies by accounting for the social, the ecological and economic detriments and costs in relation to their benefits.The flexible structures of the environmental models implemented in MOIRA-PLUS allow the application of these models to several other types of pollutants, such as heavy metals. The CDSS can be applied to complex water systems comprised of lakes, reservoirs and rivers. The main principles underpinning the functioning of the CDSS MOIRA-PLUS will be described and discussed.

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Optimal size of predictive models

Cited by 70 publications

References 5 publications

The effect of population density on shoot morphology of herbs in relation to light capture by leaves

The effect of population density on shoot morphology of herbs in relation to light capture by leaves

Effect of complexity on marine ecosystem models

MOIRA-PLUS: A decision support system for the management of complex fresh water ecosystems contaminated by radionuclides and heavy metals

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