A Critical Evaluation of the Trophic Level Concept. I. Ecological Efficiencies

A scheme of ecological efficiencies is presented in the interest of equating the terminology of various authors. Some efficiency ratios are calculated from the data of natural communities, and it is shown that a rigorous analysis indicates that several widely held assumptions about trophic dynamics, such as the existence of p rogressive efficiencies of energy utilization at higher tropic levels, cannot be substantiated. The ideas of c ommunity efficiency and c ommunity productivity are discussed, and several new ways of calculating these, based upon a consideration of the net productivities of all trophic levels or populations, are suggested.