Stability

STABILITY Definitions: • • •

dynamic equilibrium of population, community or ecosystem size & structure the ability of populations & communities to withstand environmental perturbation & to accommodate change The system respond to temporary slight disturbances by returning to its original position

3 basic types of stability: xi. Constancy A lack of change in some parameter of a system, eg. no. of species, taxonomic composition, life-form structure of a community, size of a population or some feature of the environment

ii. Resilience The ability of a system to recover & continue functioning even though its composition & structure may have changed substantially Community is able to continue functioning as a viable system iii. Inertia The ability of a system to withstand or resist perturbations

Term

Constancy

Concept A lack of change in some parameter of a system

Inertia

The ability of a system to resist external perturbations

Resilience

The ability to continue functioning after perturbation

Persistence

The survival time of a system or some component of it

Elasticity

The speed with which the system returns to its former state following a perturbation

Amplitude

The area over which a system is stable

Cyclical stability

The property of a system to oscillate around some central point or zone

Trajectory stability

The property of a system to move towards some final end point or zone despite differences in starting point

Stability of Communities Stability in structure of the community: • a constancy of trophic form of food web design • a resilience in the mode & balance of the community’s operation • interactions between populations influence the stability of the community • evidence for the actual resilience or constancy of an existing community come from the community which has been disturbed but not entirely destroyed • eg. vertebrate at logging area in West Msia: Trophic structure of the mammal returned towards its original state; Species composition & number changed, but the relative balance of numbers in different trophic categories suggest some recovery towards the original structure

• complexity of community structure

stability

• species diversity • The environmental stability permits the development of high diversity & ensure the continued stability of a high-diversity system A complex system: • greater potential to accommodate change through minor adjustments within its structure • redirecting the community relationships to absorb the perturbation • community resilience as a function of the diversity of energy-exchange pathways within the community

• a positive link between the diversity of energy exchange pathways within a web & the resilience of that system • in a stable community species are generally limited in the number of links in which they may engage •