Network trophic dynamics: the tempo of energy movement and availability in ecosystems

Energy moves with varying temporality in ecosystems, and as a result becomes unevenly aged. This paper examines the time dependency of energy-matter flux in ecosystems modeled as flow-storage networks. The temporality of passage is governed by storage, which can be viewed as transport delay, a process contributing to the availability of energy to ecosystem compartments over time. Availability is a prior condition for utilization, which nevertheless is measurable from flow considerations alone. Combined flow-storage analyses are required to determine the temporality of substance availability; flow-only analyses are sufficient to specify utilization. The relations between the two are developed. What we term “tempo” involves the transport and delay as standing stocks of variously aged substance over the direct and indirect pathways of ecosystem networks. Our concept of “mode” refers to utilization alone, without regard for timing or the age distribution of flowing substance. Temporal analysis highlights the importance of turnover time, and thus body size and mass of individual organisms, in the dynamics of energy dependencies in ecosystems.