Environmental Engineering Reference
In-Depth Information
Another example would be where the primary succession is halted by a dominant
environmental property (for example, excessive wetness). This factor maintains the
community in a condition which is subclimax and not yet climax. Over time the influence
of the arresting factor will be lessened or removed, and the subclimax community will
proceed to climax via a subsere. In order to understand fully the complexity of vegetation
patterns which one meets in the real world, it is important to know whether a particular
community is seral, subclimax, plagioclimax or climax. This is the
ecological status
of
the ecological community, and it is not always an easy attribute to discover. However, it
is worth undertaking an analysis of it, as it indicates the relation of a particular
community to the hierarchy of plant communities in the ecological succession.
CLASSIFICATION OF SUCCESSIONS
Ecological processes occurring in successions have received considerable attention from
biogeographers. One classification of seres is based on the nature of the surface from
which the primary succession starts. Those habitats where drought is the main limiting
factor are referred to as
xeroseres
. Two common situations are where bare rock
dominates (new volcanic lava or a recent scree) and where sand dominates (coastal sand
or fluvioglacial sands or aeolian sand). The former cases are
lithoseres
and the
successional processes are directed at the weathering of the bare, consolidated rock, and
the production of a soil upon it (p. 431). In the latter cases successional processes strive
to stabilize the unstable sandy environment so that stable plant and soil communities can
develop; these are
psammoseres
(p. 433). Other seres start with almost the opposite type
of conditions, unfavourable to plant growth. These are habitats dominated by water (lakes
or marshes) and hence are termed
hydroseres
. The fresh-
