Practice question

The intermediate disturbance hypothesis predicts a hump-shaped relationship between disturbance and species diversity. At very low disturbance, strong competitors can monopolize limiting resources and exclude inferior competitors, reducing coexistence. At very high disturbance, mortality or biomass destruction occurs so frequently or intensely that only rapid colonizers and highly tolerant species persist. Intermediate disturbance can prevent complete competitive exclusion while allowing enough time for slower-growing species to establish, so early and late successional taxa coexist. Disturbance may be fire, grazing, floods, storms, treefall, or physical disruption, and both frequency and intensity matter. The hypothesis is not universal: empirical studies often find monotonic, weak, or context-dependent patterns because productivity, spatial scale, dispersal, disturbance type, and evolutionary history alter outcomes. “No disturbance” is effectively the low-disturbance extreme rather than a separate route to maximum diversity. The mechanism is a balance between exclusion and environmental filtering, not a claim that moderate damage always benefits ecosystems. When applying IDH, investigators must define disturbance quantitatively and distinguish richness from evenness, since different diversity components may peak at different disturbance levels.