Ecology and garden wildlife - Principles of Horticulture - page 41

3

(a) (b)

Figure 3.8 Examples of primary succession: (a) a mountain landslide; (b) marram grass on sand dunes

X spread rapidly
X mature quickly
X produce large quantities of seed
X extend the period over which they germinate.
In fact, they have typical weed characteristics. Such
species are often referred to as opportunistic
(Figure 3.9).
The third successional stage involves larger
plants, shrubs and climbers such as bramble and
honeysuckle competing with plants in the previous
stage. Eventually, these stages are kept in check or
shaded out by trees. This final stage is described as
the ' climax ' community. In a cleared garden or newly
prepared border or vegetable plot, the pioneer species

would be annual and ephemeral weeds which emerge
first from the seed bank in the soil while the climax
species would be trees (Figure 3.10).
Through the stages of succession there is usually
an increase in the number of species found, both
plant and animal, meaning an increase in biodiversity.
These form increasingly more complex food webs
although often in the climax community just a few
species dominate. In gardens we constantly intefere
with natural succession. If succession is halted at the
beginning of the sequence, biodiversity will be low.
For example, this could be
X through constant cultivation
X repeated mowing of a lawn.

Figure 3.9 Sedge, an opportunistic species in
succession in damp habitats

Figure 3.10 A mature woodland representing the
natural climax community in Britain and Ireland