Summary: Ecological Modelling 165 (2003) 221229
Steady state of ecosystem flow networks: a comparison
between balancing procedures
Stefano Allesina, Cristina Bondavalli
Department of Environmental Sciences, University of Parma, Parco Area delle Scienze, 33/A, 43100 Parma, Italy
Received 9 August 2002; received in revised form 30 January 2003; accepted 19 February 2003
When modelling real ecosystems, a number of techniques need steady state condition to proceed in their analysis. In ecosystem
network models this means that energy entering the system exactly balances the output. Steady state, however, is not a straight-
forward outcome of network construction and, to have this condition satisfied, network analysis uses balancing procedure. This
operation leads to restructuring the weighted network, changing the values of some network flows; this can affect drastically
the results of the analysis. Presently, two algorithms are used for balancing ecosystem networks: input-based approach and
output-based approach. In the former input flows are kept constant while outputs and transfer coefficients are manipulated; the
latter requires that inputs and intercompartmental flows are modified. This paper discusses the effects of these algorithms on
some products of network analysis, in particular system level indices such as total system throughput (TST) and ascendency.
Also it suggests four new procedures that, while balancing the networks, can minimise changes on measured flows and distortion
on results of the analysis.
© 2003 Elsevier Science B.V. All rights reserved.
Keywords: Balancing algorithms; Ecological networks; Ecosystems; Simulation; Steady state