Agriculture Reference
In-Depth Information
Cape Region of South Africa
The species diversity of South African fynbos is relatively high in the absence of
fire and shows only modest increases with fire (
Table 11.2
). Increased diversity
after fire arises largely from geophytes present as dormant rhizomes, bulbs or
corms in the soil that are triggered to resprout by fire. Geophytes are an important
component of all MTC floras, and most are stimulated to flower by fire. Such
stimulation can be seen dramatically in large expanses of
Watsonia
that can arise
from rhizomes after fynbos fires. The Cape
Cyrtanthus ventricosus
is the only
clearly fire-dependent geophyte known from MTC regions. This “fire-lily” shows
an extraordinary relationship to fire, with bulbs possessing preformed flower buds
that remain dormant until smoke triggers flowering, usually within days of a fire,
regardless of season (Keeley
1993b
).
The absence of a dramatic postfire increase in diversity is in part due to the fact that
there are many geophytes present in mature fynbos, although their presence becomes
more obvious due to increased flowering after fire (Le Maitre & Brown
1992
). Often
overlooked are a small number of diminutive annuals in families such as the Scro-
phulariaceae and Campanulaceae that have smoke-stimulated germination and are
largely restricted to burned sites (C.J. Fotheringham unpublished data).
Western and South Australia
The postfire changes in species diversity of southwest Western Australia heath-
lands share many features with the Cape region shrublands, with relatively high
prefire diversity and modest increases after fire (Russell & Parsons
1978
; Bell &
Loneragan
1985
). Although resprouting of geophytes and other herbaceous per-
ennials comprises much of the increased postfire diversity, there are some
fire
ephemerals
(Bell
et al.
1984
; Pate
et al.
1985
). As in the Cape postfire flora, these
annuals comprise a relatively minor proportion of postfire biomass with most
being diminutive plants, usually less than a gram dry weight per plant. The low-
fertility soils likely play an important role in limiting the importance of annuals
due to the difficulty that fast-growing annuals have in sequestering sufficient
nutrients to reach reproductive maturity on infertile soils.
Eucalyptus
-dominated woodlands and forests comprise a mixed collection of forest
types with diverse fire regimes; however most are highly resilient to understory
surface fires. Compared with California conifer forests, the relatively open canopies
of eucalypt woodlands and forests allow the development of a rich understory flora
that persists either from resprouting or seed germination after fires (Bell & Koch
1980
; Wardell-Johnson
et al.
2007
). InWestern Australian forests as many as 5-10%
of the species are postfire ephemerals (Burrows & Wardell-Johnson
2003
).
Insights from Community Species-Area Relationships
Regional species-area curves (e.g.
Fig. 11.1a
,
b
) often differ between landscapes
and statistical coefficients of these curves are thought to reveal
important
