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