Biology 3445F Study Guide - Final Guide: Intermediate Disturbance Hypothesis, Trophic Cascade, Habitat Fragmentation
28 Jul 2017
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Types of disturbances : physical (fire, ice, waves, drought), chemical (pollution), biological (invasive species) Fire is a natural disturbance: creates mosaic landscape, reduces fuel loading, stabilises insect and disease population, recycles nutrients. Heterogeneity in the landscape promotes species richness. Time scale: duration how long it affects the community (press vs pulse, pulse = quick disturbances, frequency how often. Spatial scale spatial extent of the impact relative to size of landscape. Extent of disturbance: large disturbance may eliminate all species, small disturbance may have little or no impact. Duration: press could prevent competitive exclusion, pulse could provide differences among patches in a landscape. Most widespread agents of disturbance are due to human activity. Habitat loss, climate change and land use change. Objective: determine which forest harvest and regenerative practices best maintain biotic communities, spatial patterns of forest structure, functional ecosystem integrity. Regime shift (phase shift) change from one community state to another (communities can shift from one form to another)
