ABSTRACT
Stability as applied to an ecosystem is a particularly elusive concept. The greater the number of species the greater would be the number of species interactions and, hence, the smaller would be the change in the system as a result of the disturbance in any one biotic or a biotic component. Two other terms—perturbation and stress—are frequency used as synonyms of disturbance; or with perturbation meaning either an experimentally applied or anthropogenic disturbance and with stress applied to factors which produce large negative impacts on organisms. The reaction of an ecosystem to disturbance depends, on the one hand, on the type and degree of disturbance, i.e. the disturbance regime; and, on the other, on the vulnerability of the ecosystem to disturbance. Organisms vary in their tolerance or adaptation to varying disturbance regimes—so that disturbance in the first instance is a selective ecological agent.
