The Y-shaped energy-flow model of an ecosystem was proposed by:

Concept: In ecosystem ecology, an energy-flow model traces the route taken by the energy that producers fix during photosynthesis. A single-channel model follows one linear grazing route through successive trophic levels. A two-channel model instead recognises that the fixed energy divides at the producer base into two parallel chains — one beginning with living plant tissue and one beginning with dead organic matter — which stay linked further along, so the diagram forks like the letter Y.

Application: The Y-shaped (two-channel) energy flow model of an ecosystem was pioneered by Howard T. (H.T.) Odum in 1956. Eugene P. Odum later presented a generalized double-channel treatment as a more realistic alternative to the single-channel picture. In it, net primary production splits into a grazing food chain (green plants → herbivores → carnivores) and a detritus food chain (dead organic matter → detritivores and decomposers → their predators). The two chains share the same producer base and remain connected downstream, because organisms of the grazing chain keep adding faeces and dead tissue to the detritus pool.

Why the fork matters: in most terrestrial ecosystems only a small fraction of net primary production is actually grazed, while the bulk of it passes into the detritus chain. A single-channel model cannot represent that split, which is exactly what the Y-shaped model was designed to show.

Cross-check: the other ecologists named here are associated with different ideas.

• Raymond Lindeman — the trophic-dynamic aspect of ecology (1942) and the ten-percent law of energy transfer between successive trophic levels; that is a single-channel, linear treatment of energy flow.

• Frederic Clements — plant succession and the monoclimax theory, which treats the plant community as a developing super-organism; this describes community development over time, not the routing of energy.

Since the Y-shaped energy flow model is credited to exactly one of the ecologists named in the choices, the composite and exclusion choices do not apply. The pioneering attribution is to H.T. Odum.