Math Archives Homepage

NETWRK4: A Package of Computer Algorithms to Analyze Ecological Flow Networks

Robert E. Ulanowicz
University of Maryland
Center for Environmental & Estuarine Studies
Chesapeake Biological Laboratory
Solomons, MD 20688-0038

Sometime during the mid-1970's it became apparent that ecological modeling in the form of a set of coupled, deterministic differential equations was not going to be the panacea for analyzing whole ecosystems. In the search for alternative methods of describing the behavior of total ecosystems, various computations performed on the underlying network of flows have figured prominently (SCOR, 1981). The intention in writing these subroutines has been to collect the various algorithms into a single large program which allows an investigator to choose that analysis which best serves his needs. It is also hoped that by comparing the results of different methods (sometimes operating at different levels of aggregation) new insights will appear which would not have been possible by confining one's attention to a single approach.

Four types of analyses are performed by this routine. The outputs are presented in ascending degree of network aggregation. First, input-output structure matrices are calculated, allowing one to look in detail at the effects any particular flow or transformation might have on any other given species or flow. Next, the graph is mapped into a concatonated trophic chain (after Lindeman). Then all the simple, directed biogeochemical cycles are identified and separated from their supporting dissipative flows. Finally, global variables describing the state of development of the network are presented.

(Adapted from the documentation)
Download [125 KB].

Look at the readme file from the program.