Scope and Strategy
11
different species or between different lakes, while less weight will be placed
on detailed simulation of specific seasonal successions or laboratory experiments.
The model development starts out by reviewing some basic ideas on
lakes as open dynamical systems, and their relationship to classical inputoutput models (Chap. 2). The key concepts from classical loading models
are used as the fundament for the formulation of a more general modeling
framework, based on stoichiometric relationships in food webs. In the general framework, flows among plankton compartments are presented without reference to the control mechanisms in the pelagic flow network. Two
separate chapters (Chap. 3 and 4) are devoted to describing processes
regulating population growth and nutrient utilization in specific compartments of the plankton community.
Since primary production constitutes the major autochtoneous energy
input to plankton communities, phytoplankton form the base of the food
web. Phytoplankton also play a major role in the pelagic nutrient cycles
both as exploitative competitors for dissolved nutrients, and as vehicles for
transporting nutrients into higher trophic levels, or out of the pelagic zone.
Chapter 3 presents a simple model incorporating the necessary interrelationships between phytoplankton growth, nutrient uptake, and nutrient
utilization. Emphasis is placed on the observed parameter ranges, and how
this variability may be used to construct abstract model species with different competitive traits, while no attempts are made to model specific data
sets from any particular phytoplankton species.
Zooplankton communities in lakes with low vertebrate predation pressure appear to have a general similarity in the sense that they are usually
dominated by large cladoceran grazers. The simple community structure
makes it possible to narrow down the scope of model development to a
small set of target species, with members of the genus Daphnia as typical
representatives. Chapter 4 presents a set of submodels covering different
aspects of Daphnia biology, on both the individual and the population
level. Individual growth is described in relation to both food abundance
and nutritional quality, while population growth is described as a function
of individual reproductive output and survival probability. The asymptotic
properties of the stable age distribution are utilized to construct a simplified model of zooplankton population dynamics without age stucture.
In Chapter 5, modules from Chapters 3 and 4 are assembled into the general framework of Chapter 2, resulting in a minimal model of pelagic nutrient cycling with only three compartments: phosphorus, algae, and grazers.
With this particularly simple model structure, it is possible to explore the
conditions for local stability, extinction, and persistence by classical analytical and graphical techniques. The analytical results are supplemented by
simulations investigating nonlinear phenomena like bifurcations and periodic orbits. The model predictions are used to construct loading criteria
and trophic state indicators for biomanipulated lakes.
11
different species or between different lakes, while less weight will be placed
on detailed simulation of specific seasonal successions or laboratory experiments.
The model development starts out by reviewing some basic ideas on
lakes as open dynamical systems, and their relationship to classical inputoutput models (Chap. 2). The key concepts from classical loading models
are used as the fundament for the formulation of a more general modeling
framework, based on stoichiometric relationships in food webs. In the general framework, flows among plankton compartments are presented without reference to the control mechanisms in the pelagic flow network. Two
separate chapters (Chap. 3 and 4) are devoted to describing processes
regulating population growth and nutrient utilization in specific compartments of the plankton community.
Since primary production constitutes the major autochtoneous energy
input to plankton communities, phytoplankton form the base of the food
web. Phytoplankton also play a major role in the pelagic nutrient cycles
both as exploitative competitors for dissolved nutrients, and as vehicles for
transporting nutrients into higher trophic levels, or out of the pelagic zone.
Chapter 3 presents a simple model incorporating the necessary interrelationships between phytoplankton growth, nutrient uptake, and nutrient
utilization. Emphasis is placed on the observed parameter ranges, and how
this variability may be used to construct abstract model species with different competitive traits, while no attempts are made to model specific data
sets from any particular phytoplankton species.
Zooplankton communities in lakes with low vertebrate predation pressure appear to have a general similarity in the sense that they are usually
dominated by large cladoceran grazers. The simple community structure
makes it possible to narrow down the scope of model development to a
small set of target species, with members of the genus Daphnia as typical
representatives. Chapter 4 presents a set of submodels covering different
aspects of Daphnia biology, on both the individual and the population
level. Individual growth is described in relation to both food abundance
and nutritional quality, while population growth is described as a function
of individual reproductive output and survival probability. The asymptotic
properties of the stable age distribution are utilized to construct a simplified model of zooplankton population dynamics without age stucture.
In Chapter 5, modules from Chapters 3 and 4 are assembled into the general framework of Chapter 2, resulting in a minimal model of pelagic nutrient cycling with only three compartments: phosphorus, algae, and grazers.
With this particularly simple model structure, it is possible to explore the
conditions for local stability, extinction, and persistence by classical analytical and graphical techniques. The analytical results are supplemented by
simulations investigating nonlinear phenomena like bifurcations and periodic orbits. The model predictions are used to construct loading criteria
and trophic state indicators for biomanipulated lakes.