How much of the storage in the ecosystem is due to cycling?

•Finn׳s cycling index (FCI) computes the cycled ecosystem flow.•Develop a new storage-based cycling index (SCI).•SCI utilizes both flow and residence time.•SCI is vastly different from FCI for most systems.•SCI is a preferable index for quantifying cycling.

Cycling is the process of reutilization of matter or energy in the ecosystem. As it is not directly measurable, the strength of cycling is calculated based on mathematical models of the ecosystem. For a storage-flow type ecosystem model, throughflow is the total amount of material flowing through all system compartments per unit of time, while storage represents the total standing stock in the system. Finn׳s cycling index (FCI) is widely used to measure the cycled throughflow, the proportion of throughflow generated by cycling. Thus, although originally named after its author J.T. Finn, FCI can also be called a “flow-based” cycling index. In addition to flow, storage plays an important role in generating network properties, and therefore should be taken into account in measuring cycling. In this paper, we investigate how much of the total standing stock of matter or energy in the ecosystem is due to cycling, and formulate a storage-based cycling index (SCI), by utilizing an individual-based method to simulate the system. SCI utilizes flow values used for FCI and takes into account residence time as well. Therefore, SCI is a preferable index for quantifying cycling in ecosystems.