Vegetation development and succession - Fundamentals of the Physical Environment - page 643

Whilst the broad principles of Clements's theories of succession form the basis of our
understanding, several amendments of his basic model are now accepted. Three
alternative models are illustrated in Figure 21.4. The facilitation model mostly follows
Clements and envisages the establishment of plant communities which modify the
physical conditions so that they become favourable to late successional species. In the
tolerance model successive stages in the succession depend upon the competitive
abilities and life spans of the plants, so that, for example, the longer-lived species
associated with later stages will persist in the community. The third alternative, the
inhibition model , envisages the initial plant cover modifying the physical habitat so that
it is less favourable to colonization by other species, and succession can occur only when
the inhibitory species are removed.
The classical views of succession are thus becoming modified as it is realized that it is
a more complex process

Figure 21.3 The classification of priseres according to dry
(xero-) and wet (hydro-) starting points.
Source: After Eyre (1968).

Table 21.1 Fundamental successional processes

Term Process

Nudation Initial creation of bare surface

Immigration Arrival of available propagules

Ecesis Establishment of propagules

Reaction Interaction of plants and of plants and habitat

Stabilization Creation of equilibrium communities

Source : After Clements (1916).