Energy flow and partitioning in selected man-managed and natural ecosystems

Abstract

Energy-flow studies in many terrestrial ecosystems have been characterized by emphasis on grazing pathways. In this paper, we demonstrate the preponderance of energy-flow in detrital-saprophagic pathways, even in those systems exploited for grazing by man (e.g., grassland ecosystems). When examining a full spectrum of terrestrial ecosystem types, ranging from agro-ecosystems to herbaceous to forested ecosystems, the costs for belowground primary (root) production and maintenance are high, and predominate in several natural ecosystems studied so far. Surprisingly, agro-ecosystems remain the ecological units we know the least about, for total-system energy-flow. Making a few estimates of more realistic heterotrophic energy costs, we suggest P/R ratios for highly productive ecosystems may be <2 (1.8-2.0), and closer than had been previously claimed to some man-managed ecosystems, which have P/R ratios of from 1.2 to 1.3. Because total-system energy budgets are known for so few habitats, many more studies are needed for the developing science of ecosystem management.