A systems perspective of disturbance
Current hierarchical concepts of ecosystems provide a holistic perspective on disturbance phenomena. Organised systems function with constraints (feedbacks) that may be characterised by their process rates. Slower-acting processes constrain faster-acting processes to limit system behaviour. in the manner of a hierarchical framework. Disturbances arise when a change in process rates destabilises the system at one or more points.
The degree of disturbance impact and the nature of impact depends firstly on the process rate of the disturbance agent itself. It also depends on the temporal and spatial scales of the system. A disturbance over the short term. or in small space. may not constitute disturbance in the longer term or in larger space. A disturbance event is therefore not an absolute phenomenon but a relative phenomenon. changing with different observer perspectives. When account is taken of observation parameters. the phenomenon can be characterised more clearly.
The characterisation of disturbance will be illustrated by numerous ecological examples.