Succession and management - Ecological Applications: Toward a Sustainable World - page 218

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

3 26 46 149

Successional stages (years)

Bothriochloa ischaemun
Lespedeza davurica
Artemisia gmelinii

Seraria viridis
Stipa bungeana
Artemisia scoparia

Fig. 8.2 Variation in relative importance of six species on four plots abandoned by farmers
for known periods of time (3, 26, 46 and 149 years) during a secondary succession on the
Loess Plateau in China. In the fi rst stage of succession Artemesia scoparia and Seraria viridis
were most characteristic; at 26 years Lespedeza davurica and S. viridis dominated; at 46 years
Stipa bungeana , Bothriochloa ischaemun , A. gmelinii and L. davurica were most important;
fi nally at 149 years B. ischaemun and A. gmelinii were dominant. The early-successional
species were annuals and biennials with high seed production. By 26 years, the perennial
herb L. davurica had outcompeted A. scoparia . The 46-year-old plot was characterized by the
highest species richness. The dominance of the 'climax' grass B.ischaemun at 149 years was
related to its perennial nature, ability to spread by vegetative means and its high competitive
ability. (After Wang, 2002.)

occur very frequently, succession cannot proceed far beyond the pioneer stage and few species
are represented. By contrast, if disturbances are very infrequent much of the mosaic will consist
of late-successional species that have outcompeted and excluded the pioneers - species richness
is again likely to be relatively low. But in situations where disturbances occur at an intermediate
frequency, species from all successional stages are represented and the area's species richness
can be expected to be at a maximum. This is the essence of the intermediate disturbance hypothesis
(Connell, 1978).

8.2 Managing
succession for
restoration

The restoration of natural communities demands a thorough understanding of the
theory of succession (Box 8.1). First, managers need to be aware of the timetables
of natural recovery of plant and animal communities (Sections 8.2.1, 8.2.2). But just
as important is recognition of the underlying successional process, something that
varies from case to case: competition-colonization trade-off (Section 8.2.3), succes-
sional niche (Section 8.2.4), facilitation (Section 8.2.5), interactions with enemies
(Section 8.2.6).

8.2.1 Restoration
timetables for plants

In many parts of the world fi res are now less frequent but more intense, blazing over
larger spatial scales than was the case before human infl uence. By taking active steps
to reduce the likelihood of forest or grassland fi res, highly fl ammable 'fuels' have
been allowed to build up (including living biomass and the dead organic matter that
accumulates beneath vegetation), so that when a fi re is started by lightning or a
carelessly discarded cigarette it burns long and hard.