Food web framework for size-structured populations
(2010)cite arxiv:1004.4138.Аннотация
We present for the first time a generic food web framework suitable for
modelling systems where the populations have a large difference between size as
offspring and size at maturation. In such systems individuals encounter
predators and prey from different trophic levels as they grow (life history
omnivory) -- an ecological fact that traditional unstructured food web models
ignore. The population dynamics of each population is calculated from
individual level processes, and each species is characterised by the trait:
size at maturation (m*). Parameters are made species independent through
scaling with individual body size and m*. Their values are determined from
cross-species analysis in the literature of marine ecosystems. Emphasis is put
on the rule for allocation of energy between somatic growth and reproduction to
ensure realistic growth trajectories of individuals. By assuming that the
community spectrum follows a perfect power law we can simplify the model and
find the equilibrium solution analytically (equilibrium size-spectrum theory,
EQT). Using the full model we create a large ensemble of communities and find
that the emerging average community structures fit EQT predictions. Model
predictions allow us to pose an extended Sheldon hypothesis: `The total biomass
of individuals ordered in logarithmically spaced groups of m* is approximately
constant'. Only species size spectra are found to differ from the EQT
prediction as they do not follow power laws. Through comparison with EQT we
find that individuals are exposed to an additional density dependence
continuously distributed throughout their life. This density dependence
decreases survival probability continuously throughout life and is important
for mediating coexistence in the dynamic model. ...
Описание
Food web framework for size-structured populations