Practice question

Odum’s classic strategy of ecosystem development proposes that nutrient cycles become increasingly closed, or “tighter,” as succession proceeds. Early communities have small nutrient pools in biomass, weak retention, and relatively large losses through runoff or leaching. As vegetation, roots, decomposers, and soil organic matter develop, nutrients released by decomposition are captured more efficiently and reused within the community. Longer food chains and greater biological regulation can further slow their escape. Mature systems therefore tend to conserve limiting elements, although disturbance can abruptly reopen cycles. The model also predicts rising biomass, structural complexity, and diversity, not decreases. Early stages are commonly associated with rapidly reproducing, dispersive species, whereas later stages favour more competitive and persistent strategies. Total entropy production is not summarized by a simple statement that entropy merely increases with time. Odum’s scheme is an idealized set of tendencies rather than a universal law; actual trajectories depend on climate, soils, and disturbance. Still, improved internal nutrient retention directly explains why tighter cycling is the expected developmental trend.