Agriculture Reference
In-Depth Information
Fig. 7.8
Strandveld vegetation along the coast of the Western Cape, South Africa. (Photo by Jon
Keeley.)
Less Fire-tolerant Ecosystems: Strandveld, Thicket, Forest
As discussed above, the fire-prone shrublands of the Cape region, fynbos and
renosterveld, generally have much lower biomass than expected for the level of
annual precipitation. These fire-prone formations often abut taller scrub and
forest vegetation that occur in fire refugia such as river valleys, deep ravines, scree
slopes (
Fig. 7.4
; Geldenhuys
1994
) and adjacent to the ocean as with strandveld
(
Fig. 7.8
) There are striking differences in floristic composition, structure, and
functional attributes between the fire-prone and less flammable formations. The
latter are dominated by broadleaf species that, unlike fynbos shrubs, cast dense
shade. Also unlike fynbos, vertebrate-dispersed fruits are common and fire-stimu-
lated recruitment traits are absent (Manders
et al.
1992
). Seeds are short lived,
there are no serotinous species, and no fire-stimulated flowering. Analogous
vegetation is known as
vine thicket
or
rainforest
in Australia (Bowman
2000
).
Analogues are less obvious in other MTC regions but would include closed forest
formations such as temperate forests where fire is an irregular event and unim-
portant for recruitment. These formations would have been considered
climax
vegetation in older literature because they are self-maintaining, at equilibrium
with the climate, and cannot be invaded except after catastrophic disturbance
(Phillips
1931
).
Forest and thicket patches do occasionally burn but fires seldom penetrate more
than 50-100 m. However, under extreme weather conditions, fires may burn larger
forest patches. Following weeks of bergwinds (see
Box 1.3
), an extreme fire event
occurred in the late 1860s and is said to have destroyed extensive forest patches in
the southern Cape region, the largest forested area in South Africa (Phillips
1931
).
