PE EIE[R-Rg RESEARCH ON - HJ Andrews Experimental Forest

in the restrictions of the physical environment
are being tackled . Since the
four lakes in this study have evolved to
their present structure in the presence of
different nutrient stresses we might
expect them to exhibit various capacitie s
to conserve and cycle nutrients .
4. Effect of community structure on productivity
and distribution of energy : Th e
production of herbivores (zooplankton )
cannot be explained entirely by production
of primary producers (phytoplankton).
The physical form of the production
(i.e., size distribution or colonia l
form of algal cells) may preclude consumption
by zooplankton . However ,
zooplankton may in fact contribute to
changes in the physical form of primar y
production by being size-selective
feeders. Since changes in the form an d
species composition of phytoplankto n
communities are indices of pollution an d
eutrophying environments this process i s
being investigated .
In the same way that changes in th e
physical form of phytoplankton production
may control the production of zoo -
plankton, the community structure, siz e
distribution, and spatial distribution o f
zooplankton control the feeding behavior
and subsequent production o f
predators .
The terminal link in the food web of three
of the study lakes is the community of fis h
species . Much literature has been devoted to
models which try to explain the populatio n
dynamics of these organisms without incorporating
their interaction with the environment
. The communities of fish can influenc e
the nature of production by altering th e
community structure of other vertebrate an d
invertebrate communities upon which the y
feed and indeed may alter the entire community
(Hurlbert et al . 1972). Their own production
dynamics are related to the structure
and abundance of the prey communities an d
also to mortality dynamics which are deter -
mined by the state of the physical environment
at critical life stages . Three projects wil l
bear upon the questions related to the fis h
community .
Presently, a three submodel system (figs . 6
and 7) is being used to develop the propose d
field studies ; these are organized around water
column, bottom related, and higher consumer
processes . These subsystems were chose n
because the couplings within each are mor e
tightly linked and the span-of-time resolution s
OVERALL SYSTE M
Figure 6 . Overall system categories.
LAKE SUBSYSTEM (C)
NIGHE R
CONSUME R
DYNAMIC S
(C? ,
Figure 7. Lake subsystem categories.
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