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#Odum's model

2 public questions tagged with this topic.

Ecosystem Efficiency and Decomposition

Which component represents energy stored in Odum's model?

In simplified versions of Odum’s universal energy-flow model, S denotes energy stored as biomass or accumulated organic matter. Incoming assimilated energy is partitioned among respiration, production, storage, and exported or unassimilated pathways. Storage is a stock measured at a time, whereas production and respiration are rates over time. Recognizing that distinction prevents confusing standing biomass with productivity: a system may have a large S because biomass persists even when its current production rate is modest. Mass loss alone cannot identify mechanism, because leaching, fragmentation, respiration, assimilation, and stabilization can produce different fates for carbon and nutrients. The distinction between gross transformation and net nutrient release is important: simultaneous microbial uptake can conceal substantial biochemical turnover. Environmental effects are often nonlinear; drought suppresses microbial access to substrates, waterlogging restricts oxygen, and extreme heat can reduce activity despite faster kinetics. Substrate stoichiometry links carbon processing to nutrient demand, so identical mass loss can accompany mineralization in one litter type and immobilization in another.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3

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Ecosystem Efficiency and Decomposition

In Odum's model, the energy used to build new tissue is:

“P” for in odum's model, the energy used to build new tissue is. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The remaining alternatives—“R”, “A”, “I”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3

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