Potential of combining Emergy and Ecological Network Analysis for studying ecosystem function

LUCÍA ZARBÁ; MARK T. BROWN

Gainesville

Congreso; Emergy Synthesis 9: Theory and Applications of the Emergy Methodology; 2016

Ecosystem functioning depends in part on system level emergent properties thatcan only be captured through holistic approaches that recognize their complexnature. This is a very challenging endeavor and methods are yet not polished.This study is a pilot exploration of the common ground between EcologicalNetwork Analysis (ENA) and emergy theory, using two trophic networks as casestudies. We suggest that combining ideas from both frameworks can helpovercome some limitations. ENA developed a comprehensive battery of indicesfor describing system?s structure and function based on network patterns ofstocks and flows. However these analyses are constrained by the unit (usuallyenergy) chosen as the medium for the interactions (usually trophic): it dictateswhich elements can be included and the value of their connections. Emergydeveloped a way to transform everything into equivalents of a common unit,making possible quantitative comparisons within a network with diverseinteractions. Also, emergy is conserved through transactions, ensuringcomparative representation of events occurring all along the path. ENAconducted upon an emergy-based matrix showed 1) changes in the distributionof the relative importance along the network, 2) an increased protagonism ofhigher trophic level organisms, and 3) higher values of cycling, average pathlength, and the ratio indirect to direct effects. In addition, correlations (in logscale) between emergy importance value and the ascendency coefficient(r=0.957 and r=0.991) suggest a strong similarity in their essence. The data alsoexhibits an exponential relation between trophic level and transformity.