Post by cjm on Jan 3, 2016 16:12:33 GMT
A good basic introduction which often gets lost in abundantly illustrated books like this.
Manning: Fynbos, Struik (2007), pp 8-23
THE WORLD OF FYNBOS
Fynbos is famous not only for the diversity and
unusual composition of its plant species but also
for the sheer beauty of many of its wildflowers.
This unique vegetation is synonymous with
the southern tip of Africa, where it occupies a
crescent of country at the toe of the continent.
reaching from the plateau above Vanrhynsdorp
in the northwest to the city of Port Elizabeth in
the southeast. Long recognised as the smallest of
the six floral kingdoms of the world, this region is
now more properly known as the Cape Florstic
Region and is home to one of the world's richest
floras. Gathered within an area of 90 000 km2 are
almost 9 000 species of flowering plants, two-
thirds of which are found nowhere else on Earth.
lt is small wonder that Conservation International
(a United States-based organisation concerned
with conserving the Earth's living heritage) has
identified the Cape Floristic Region as one of
the +- 30 critical biological hotspots on Earth.
Pre-eminent among the botanical riches of the
region is fynbos.
History of fynbos
The first inkling of this extraordinary flora from
Africa to reach scientists arrived in the form of
a dried flowerhead of Protea neriifolia, gathered
from the slopes above False Bay by the crew of a
passing Dutch East Indiaman. European botanists
were understandably baffled by its resemblance
to a thistle, but this first tentative harbinger was
soon followed by the arrival of bulbs of several
species of Amaryllis, Hyacinth and Iris. The
flowering of these bulbs in Holland in the first
years of the 17th century ignited a passion for
fynbos flowers that has shown no sign of abating
Early botanical visitors to Cape Town were
overwhelmed by the local flora. Swedish
naturalist Andrew Sparrman, who visited the
region in the latter half of the 18th century,
was among the first to experience its wonders.
His journal entry for April I772 records his
excitement: 'At first almost every day was a rich
harvest of the rarest and most beautiful plants;
at every step we made one or more new
discoveries’ - and this was written in autumn,
when relatively few species are in flower. Other
early botanical visitors to Cape Town were
similarly entranced. 'All that I had pictured to
myself of the riches of the Cape in botany, was
far surpassed by what I saw in this day's walk. At
every step a different plant appeared; and it is
not an exaggerated description, if it should be
compared to a botanic garden so great was
the variety everywhere to be met with,’ enthused
the English explorer William Burchell in his
journal entry for the last week of November 1810.
By contrast. the early Dutch residents at the
Cape were too preoccupied with more mundane
matters to take much interest in the local vegeta-
tion, surpnsing Burchell with their indiscriminate
and rather dismissive reference to the 'glorious
heaths’ of the area as mere bosjes (bushes).
The term fynbos (or fynbosch), recorded in
the Tsitsikamma area by John Noble in 1868,
was first formally used only in the early 20th
century, when ecologist John Bews cited it
as 'applied by the inhabitants of the Cape to
any sort of small woodland growth that does
not include timber trees’. Well into the 20th
century, Cape botanists continued to describe
the vegetation either as macchia (borrowing
the term from the Mediterranean basin), or as
sclerophyll bush or shrub. it was only in the latter
half of the century that the term fynbos gained
international currency as the appropriate name
for the distinctive vegetation of the southwestem
Cape, taking its place alongside kwongan,
matorral, Chaparral and maquis (macchia), the
locally derived names for analogous heathland
communities in southwestern Australia,
Chile, California and the Mediterranean basin
respectively.
Fynbos is one of the more distinctive of the
many vegetation types that occur in southern
Africa, an observation that amateur South African
botanist Harry Bolus made as early as 1874. 'l
believe that there exist few botanical boundaries
as rigid [as that which separates the Cape flora
from that of the interior]‘, he wrote to Sir Joseph
Hooker, President of the Royal Society. His
suggested boundary for the Cape flora conforms
closely to that still used today to delimit the Cape
Floristic Region.
Fynbos distribution
As the dominant vegetation of the southwestern
Cape, fynbos occurs in several bands along the
west and southern Cape coasts. from north of
Clanwilliam in the west to Port Elizabeth in the
east (see map below). These bands. or belts,
conform largely to the parallel sandstone and
quartzite formations of the Cape Fold Mountains.
and also clothe more or less extensive exposures
of sand and limestone along the coastal shelves
By far the greatest portion of fynbos vegetation
is contained within the boundaries of the Cape
Floristic Region but suitable soils support smaller
enclaves of fynbos well beyond its borders.
Along the West Coast, coastal sands and their
associated communities of sand-plain fynbos
extend for some distance northwards. almost to
the Namibian border and outcrops of quartzitic
rock along the southern Cape coast allow grassy
fynbos to thrive as far east as Grahamstown.
Beyond this, outlying fynbos communities occur
on sandstone outcrops in southern KwaZulu.
Natal near Port Edward, and scattered patches
can be found on outcrops of sandstone, quartzite
and basalt along the edge of the Drakensberg
Mountains and eastern Escarpment, northwards
into eastern Zimbabwe. The fynbos communities
of the eastern seaboard, although structurally
similar to the true Cape fynbos of the Cape
Floristic Region and Namaqualand, differ from it
floristically and are distinguished from it as Afro-
montane and Afro-alpine fynbos. In this book we
consider only Cape fynbos.
Defining fynbos
Much of the distinctive character of fynbos is the
result of the predominance of a relatively small
number of plant groups. Indeed, almost half of
the total species are accounted for by just 33
Cape floral elements, or lineages - defined as
those groups that appear to have originated in
the Cape and most of whose descendants are still
there. The remaining species derive from groups
that are more widespread outside of the Cape.
Although generally easy to recognise, fynbos
is not as readily defined. Not only does it contain
a diversity of plant communities itself, but fynbos
also shares the Cape Floristic Region with several
other vegetation types, including renosterveld,
karroid shrubland, various thicket types and
forest. ln addition, fynbos-like communities occur
outside of the boundaries of the Cape Floristic
Region, most especially along the edge of the
interior escarpment to the north and northeast.
As a whole, fynbos is most inclusively defined
as an evergreen, hard-leafed shrubland occurring
on nutrient-poor soils, especially those derived
from heavily leached sandstones or limestones;
dominated by small- and leathery-leafed shrubs
associated with evergreen, grasslike perennials;
and comprising essentially members of plant
groups that are characteristic of the Cape Floristic
Region. This definition includes both true Cape
fynbos, recognised particularly by the presence
of restios, as well as the outlying Afro-montane
fynbos communities, which lack restios.
Fynbos mostly occurs on acidic (pH 4.4-7.0),
coarse-grained soils that are poor in nutrients,
especially nitrogen and phosphorus. It rarely
develops where the annual rainfall is less than
400 mm per annum or where droughts are
common. In its adaptation to relatively infertile
soils, fynbos is analogous to the heathlands of
other Mediterranean regions.
The fynbos definition excludes renoster shrub
land - another evergreen, fine-leafed vegetation
type, dominated by the shrubby, granular-
leafed renosterbos, Elytropappus rhinocerotis
(Asteraceae), that once covered large tracts of
the more fertile clay soils of the coastal forelands
and intermontane valleys in the southwestern
Cape, but has now largely disappeared under the
plough. Renosterveld is especially rich in bulbs
but otherwise poor in typical fynbos plant groups
- most significantly proteas, ericas and restios
It replaces fynbos on richer soils with a higher
pH and a rainfall or around 600 mm per annum,
but both give way to karroid shrublands under
conditions of lower winter rainfall, around 250 -
300 mm per annum. With increasing summer
rainfall, fynbos is supplanted by other vegetation
types, including thicket, savanna and grassland,
except on nutrient-poor soils.
Fynbos is not strictly a Mediterranean
vegetation, in that it is not confined to regions
of winter rainfall. The real determinants of
fynbos vegetation appear to be limitations both
on growth and on the annual replacement of
leaves. These are most obviously the result of
an absolute shortage of nutrients in intrinsically
poor soils, such as the sandstones of the Cape
Fold Mountains. Nutrient deficiencies also occur
in richer soils where nutrients have either been
leached out of the surface layers by heavy rains
or are just not available to the plants for other
reasons, such as low temperatures or soil acidity.
This explains why patches of fynbos vegetation
occur on nutrient-poor soils in subtropical
southern KwaZulu-Natal, as well as on the highly
leached basalt soils in the high Drakensberg.
The dominance of fynbos in the southwestern
Cape, in both strictly Mediterranean as well as
temperate maritime climates, is primarily the
result of the extensive exposures of nutrient-poor
soils in the region.
Recognising fynbos
Fynbos is characteristcally a hard-leafed,
relatively open shrubland, about 1-3 m tall, often
with scattered taller bushes protruding above
the canopy. Fynbos shrubs vary greatly in height
and density but are mostly richly branched, with
twisted trunks. True trees are virtually absent. The
...
Fynbos diversity
Cape fynbos plant communities cover over
41 000 km2,or a little under half the total area
of the Cape Floristic Region, but are estimated
to contribute 70-80 per cent of the region's
flora, making fynbos easily the most diverse
vegetation type in this part of the world.
The entire Cape Floristic Region averages
94 unique species per 1 000 km2, making it
much more diverse than many other parts
of the world. California and southwestern
Australia, two other Mediterranean regions,
have respective average diversities of 14 and
just under 12 unique species per 1 000 km2 ,
and southern Africa as a whole averages just
8 unique species per 1 000 km2. Within the
Cape Floristic Region, fynbos alone may contain
between 150 and 170 unique species per
1 000 km2, an astonishing two or three times
that measured for tropical rainforests. How is
this extraordinary diversity possible? The secret
lies in the scale at which it is measured.
At the local scale, the number of species
occurring in a single plot of, say, one square
kilometre, can be counted and compared with
counts from similar plots in other vegetation
types.This gives us a measure of local diversity
(known technically as alpha diversity), which
averages around 65 species per km2 for Cape
fynbos.This is slightly lower than available
figures for renoster shrublands (84 species
per km2) but compares well with figures for
Australian kwongan heathlands; Californian
chaparral communities, at 30 species per km2,
are much less diverse. At this scale, tropical
rainforests are easily the most diverse habitats
on Earth, with a local richness ranging between
130 and 190 species per km2. On this basis,
fynbos, although diverse, is not extraordinarily
so. How then do we explain the enormous
diversity for the vegetation type as a whole?
Botanists have now established that the
main source of fynbos diversity lies not in
the absolute number of species found at any
particular site but in the proportion of species
that is shared between sites, either nearby but
with a different ecology, or distant and with a
similar ecology (measures known respectively as
beta and gamma diversity). Measured in this way,
the diversity of Cape fynbos is far higher than
other vegetation types -the result of the high
rate at which species give way to others across
environmental and geographical gradients. Put
another way,Cape fynbos is characterised by
exceptionally high numbers of highly localised
species - those that are restricted to a single,
small area, sometimes less than one square
kilometre. In sites that are as little as 25 km apart,
for instance, between half and two thirds of the
species have been replaced by different ones.
This is in sharp contrast to tropical forests, where
individual species are widely scattered,and is
one of the reasons it is so difficult to identify
fynbos species: each locality is likely to have a
large proportion of different species.
This fynbos characteristic was already
evident to the indefatigable Lady Anne
Barnard, wife of the Secretary to the First British
Administration of the Cape, soon after her
arrival. ln her diary entry for 10 October 1799,
she notes'... l was more than ever confirmed
in the opinion that a botanist here must live a
year or two in the country for he must be in
many places at once as the plains, the marshy or
dry soils, the tops of mountains or the gullies all
produce very different flowers from each other
in the same season'.
Quite why nutrient-poor soils should foster .
such a high diversity of species is not clear.
One suggestion is that even slightly differing
ratios of limiting soil nutrients constitute
14
microenvironments that are sufficiently different
to permit a greater variety of plant species to
occupy a given area than is the case in more
fertile soils, where minor differences in nutrient
ratios are not significant. While this is an attractive
explanation for the relatively high levels of local
diversity in fynbos, it does not explain the rapidity
with which many species give way to others over
short distances, or the high proportion of local
species. Certainly, the diversity of microclímates
that characterises the Cape Floristic Region as a
result of its varied topography, soils and rainfall
patterns is important in stimulating the evolution
of different species. The role of fire in disrupting
the succession of species and in providing
opportunities for different survival strategies must
also not be overlooked (see below). ln addition,
the particular distribution of nutrient-poor and
nutrient~richer soils relative to one another is
probably important in fostering the evolution of
new species. It is likely that one of the key factors
in the floristic diversity of the Cape is that bands
of these soils, each bearing their own distinctive
fynbos or renosterveld communities alternate
so regularly with one another. The relative
isolation of the deposits or outcrops of sandstone
within a surrounding sea of shale is likely to have
encouraged the evolution of different species on
each of the sandstone islands.
Fire and fynbos
Fynbos is a fire-adapted vegetation and evidence
suggests that, in the absence of regular fires,
all but the drier fynbos types would become
dominated by trees. fynbos can thus be viewed
as a fire-dependent vegetation type, along with
grasslands and savannas.
The infertility of fynbos soils means that the
recycling of soil nutrients is essential for fynbos
survival. Fire is the motor that drives this cycle,
and fires at appropriate intervals are not only
an integral, but also an essential part of fynbos
ecology. Fires are more common in fynbos than in
any of the other heathlands around the world. This
is a result of the extreme flammabilityof the dried,
often intricately branched shrubs and restioids,
and it is rare to find stands of fynbos vegetation
that are more than 20 years old. Fires rejuvenate
the vegetation by removing moribund growth
and recycling precious nutrients back into the soil.
They also remove the choking canopy that has
grown up during the intervening years, allowing ,
light to reach the soil surface.
...
15
...
The origins of fynbos
Although the appearance of the first flowering
plants dates back to around 150 million years
ago or more, their real flowering began about
90 million years ago, and it took another 10
million years before they began to dominate
the fossil pollen record. Until then, flowering
plants appear to have eked out an existence in
the understorey of temperate coniferous forests
and among the fields of ferns that covered the
Earth, where they were probably restricted to1
disturbed habitats.
Most of southern Africa until around 60
million years ago was blanketed by subtropical
forest, although there are sure to have been
pockets of arid-adapted vegetation in dry valleys
and on shallow soils. More recent pollen samples
from the West Coast and Cape Peninsula
corroborate the occurrence of distinctly
tropical vegetation here, including palms
and other tropical trees and shrubs, as recently
as 10 million years ago, and these warm,
humid conditions appear to have
extended into the central Karoo. However,
the discovery of fossil pollen of fynbos
families, such as restios, proteas and ericas,
from deposits in Namaqualand that
have been dated to between 71 and 64 million
years ago, indicates that these typical Cape
elements were already present at this early time,
probably as part of the forest itself.
Around 30 million years ago, the climate
in southern Africa became drier and more
seasonal as a result of the establishment of the
South Atlantic high-pressure cell, which drives
our modern climate. The evolution of corms
from rhizomes in the southern African members
of the Iris family, as an obvious adaptation
to seasonal climates, appears to date from
this time. Prior to this. the climate around
the world had been largely warm and humid.
The elevation of the central southern African
plateau around 10 million years ago and the
more or less concomitant establishment of the
Benguela Current along the West Coast further
increased the aridity in the western half of the
subcontinent and initiated the establishment
of present weather patterns in the subregion.
The development of the modern winter-rainfall
climate in southern Africa, which led to the
current expansion of fynbos vegetation, is
21
thus a relatively recent event dating back a
mere three to five million years. More recently,
the southern African climate has undergone
several modest oscillations coinciding with
the recurrent ice ages that devastated the
flora and fauna of the northern hemisphere.
Although relatively small, these oscillations
have been enough to push the boundary of
the winter-rainfall region far to the northwest
at times, most recently as 17 000-15 000 years
ago. This would have allowed temperate plant
communities such as fynbos to expand their
range considerably beyond their current limits.
Indirect dating of the start of the
diversification of the Cape lineages for which
sufficient data is available from DNA studies,
gives dates ranging from 18 million years ago
for Pelargonium to eight million years ago
for Phylica. This evidence, although scant,
suggests that climatic changes, especially
increasing aridity, were instrumental in the
evolution of fynbos. As for the ancestors of
fynbos, it would appear that several of the
earliest, dating to around 80 million years
ago, were drawn from groups that are shared
with Australasia. These include the Protea, Iris,
Restio and Geissoloma families. At this time,
Antarctica and Australia were still more or less
contiguous, forming a great southern landmass
that could well have been the ancestral home
of these families. Dispersal to southern Africa
across the nascent Indian Ocean would not
have posed the problems that it does today.
Other fynbos families, such as the Penaea and
Stilbe families, seem to have been derived
from lineages that originated in tropical Africa,
with only a few, such as Palmiet. having their
nearest relatives in South America. Many of the
Cape elements found today in the mountains
of tropical Africa appear to have migrated
northwards to their current location rather
than southwards from there, as was originally
postulated for the genus Protea. In summary,
therefore, there is no single source from which
the ancestors of Cape fynbos were drawn.
Much of the richness at the species level must
be of recent age, having evolved since the
establishment of the modern climate in the
past few million years, and arising in an 'orgy
of speciation' that was almost certainly assisted
by the periodic pulses that characterise our.
current climate.
22
Fynbos conservation
The high diversity of fynbos and the large number
of local endemics dramatically increase the danger
of extinction for a substantial proportion of its
plants. In general terms, small areas with a great
diversity of plant species are most likely to have the
greatest number of rare and endangered species.
This is a consequence of the high proportion of
very localised species in such regions. Fynbos is
especially vulnerable, and the Cape Peninsula is
a typical example, with 161 species of flowering
plants endemic, or restricted, to it.
Worldwide, around 10 per cent of all
plant species are rare or endangered. In the
southwestern Cape, where two thirds of the
species are endemic, nearly one-third are rare
or endangered. This amounts to more than
2 000 fynbos species.
The number of species threatened with
extinction in South Africa has risen dramatically
since the last survey of rare and threatened
plant species was completed in 1997. ln the
Protea family, for instance, the number of
threatened species has risen from 22 per cent to
60 per cent, or almost two-thirds of the species.
Similar trends are evident in other families.
The greatest threat to the plants of the
southwestern Cape is the transformation of
habitat for urban development, agriculture
and silviculture. While species from lowland
habitats are most threatened, the increasing
cultivation of crops such as rooibos is
putting pressure on upland species as well.
Urban sprawl around Cape Town has caused
the extinction of several species in recent
years. Another major threat to fynbos is the
encroachment of alien vegetation, especially
Australian wattles and hakea. Fires at too-
frequent intervals pose a threat to the local
survival of fynbos species that are unable to re-
establish under such a regime. Still others are
under threat from the collection of wild plants
for traditional medicinal use.
The responsibility for conservation rests
with the individual, and everyone can make
a difference. Join local interest groups
in your neighbourhood concerned with
conservation, or adopt and protect a small
site with threatened species on it. With so
many species surviving precariously on tiny
fragments, fynbos needs all the help it can
get to survive.
...
THE WORLD OF FYNBOS
Fynbos is famous not only for the diversity and
unusual composition of its plant species but also
for the sheer beauty of many of its wildflowers.
This unique vegetation is synonymous with
the southern tip of Africa, where it occupies a
crescent of country at the toe of the continent.
reaching from the plateau above Vanrhynsdorp
in the northwest to the city of Port Elizabeth in
the southeast. Long recognised as the smallest of
the six floral kingdoms of the world, this region is
now more properly known as the Cape Florstic
Region and is home to one of the world's richest
floras. Gathered within an area of 90 000 km2 are
almost 9 000 species of flowering plants, two-
thirds of which are found nowhere else on Earth.
lt is small wonder that Conservation International
(a United States-based organisation concerned
with conserving the Earth's living heritage) has
identified the Cape Floristic Region as one of
the +- 30 critical biological hotspots on Earth.
Pre-eminent among the botanical riches of the
region is fynbos.
History of fynbos
The first inkling of this extraordinary flora from
Africa to reach scientists arrived in the form of
a dried flowerhead of Protea neriifolia, gathered
from the slopes above False Bay by the crew of a
passing Dutch East Indiaman. European botanists
were understandably baffled by its resemblance
to a thistle, but this first tentative harbinger was
soon followed by the arrival of bulbs of several
species of Amaryllis, Hyacinth and Iris. The
flowering of these bulbs in Holland in the first
years of the 17th century ignited a passion for
fynbos flowers that has shown no sign of abating
Early botanical visitors to Cape Town were
overwhelmed by the local flora. Swedish
naturalist Andrew Sparrman, who visited the
region in the latter half of the 18th century,
was among the first to experience its wonders.
His journal entry for April I772 records his
excitement: 'At first almost every day was a rich
harvest of the rarest and most beautiful plants;
at every step we made one or more new
discoveries’ - and this was written in autumn,
when relatively few species are in flower. Other
early botanical visitors to Cape Town were
similarly entranced. 'All that I had pictured to
myself of the riches of the Cape in botany, was
far surpassed by what I saw in this day's walk. At
every step a different plant appeared; and it is
not an exaggerated description, if it should be
compared to a botanic garden so great was
the variety everywhere to be met with,’ enthused
the English explorer William Burchell in his
journal entry for the last week of November 1810.
By contrast. the early Dutch residents at the
Cape were too preoccupied with more mundane
matters to take much interest in the local vegeta-
tion, surpnsing Burchell with their indiscriminate
and rather dismissive reference to the 'glorious
heaths’ of the area as mere bosjes (bushes).
The term fynbos (or fynbosch), recorded in
the Tsitsikamma area by John Noble in 1868,
was first formally used only in the early 20th
century, when ecologist John Bews cited it
as 'applied by the inhabitants of the Cape to
any sort of small woodland growth that does
not include timber trees’. Well into the 20th
century, Cape botanists continued to describe
the vegetation either as macchia (borrowing
the term from the Mediterranean basin), or as
sclerophyll bush or shrub. it was only in the latter
half of the century that the term fynbos gained
international currency as the appropriate name
for the distinctive vegetation of the southwestem
Cape, taking its place alongside kwongan,
matorral, Chaparral and maquis (macchia), the
locally derived names for analogous heathland
communities in southwestern Australia,
Chile, California and the Mediterranean basin
respectively.
Fynbos is one of the more distinctive of the
many vegetation types that occur in southern
Africa, an observation that amateur South African
botanist Harry Bolus made as early as 1874. 'l
believe that there exist few botanical boundaries
as rigid [as that which separates the Cape flora
from that of the interior]‘, he wrote to Sir Joseph
Hooker, President of the Royal Society. His
suggested boundary for the Cape flora conforms
closely to that still used today to delimit the Cape
Floristic Region.
Fynbos distribution
As the dominant vegetation of the southwestern
Cape, fynbos occurs in several bands along the
west and southern Cape coasts. from north of
Clanwilliam in the west to Port Elizabeth in the
east (see map below). These bands. or belts,
conform largely to the parallel sandstone and
quartzite formations of the Cape Fold Mountains.
and also clothe more or less extensive exposures
of sand and limestone along the coastal shelves
By far the greatest portion of fynbos vegetation
is contained within the boundaries of the Cape
Floristic Region but suitable soils support smaller
enclaves of fynbos well beyond its borders.
Along the West Coast, coastal sands and their
associated communities of sand-plain fynbos
extend for some distance northwards. almost to
the Namibian border and outcrops of quartzitic
rock along the southern Cape coast allow grassy
fynbos to thrive as far east as Grahamstown.
Beyond this, outlying fynbos communities occur
on sandstone outcrops in southern KwaZulu.
Natal near Port Edward, and scattered patches
can be found on outcrops of sandstone, quartzite
and basalt along the edge of the Drakensberg
Mountains and eastern Escarpment, northwards
into eastern Zimbabwe. The fynbos communities
of the eastern seaboard, although structurally
similar to the true Cape fynbos of the Cape
Floristic Region and Namaqualand, differ from it
floristically and are distinguished from it as Afro-
montane and Afro-alpine fynbos. In this book we
consider only Cape fynbos.
Defining fynbos
Much of the distinctive character of fynbos is the
result of the predominance of a relatively small
number of plant groups. Indeed, almost half of
the total species are accounted for by just 33
Cape floral elements, or lineages - defined as
those groups that appear to have originated in
the Cape and most of whose descendants are still
there. The remaining species derive from groups
that are more widespread outside of the Cape.
Although generally easy to recognise, fynbos
is not as readily defined. Not only does it contain
a diversity of plant communities itself, but fynbos
also shares the Cape Floristic Region with several
other vegetation types, including renosterveld,
karroid shrubland, various thicket types and
forest. ln addition, fynbos-like communities occur
outside of the boundaries of the Cape Floristic
Region, most especially along the edge of the
interior escarpment to the north and northeast.
As a whole, fynbos is most inclusively defined
as an evergreen, hard-leafed shrubland occurring
on nutrient-poor soils, especially those derived
from heavily leached sandstones or limestones;
dominated by small- and leathery-leafed shrubs
associated with evergreen, grasslike perennials;
and comprising essentially members of plant
groups that are characteristic of the Cape Floristic
Region. This definition includes both true Cape
fynbos, recognised particularly by the presence
of restios, as well as the outlying Afro-montane
fynbos communities, which lack restios.
Fynbos mostly occurs on acidic (pH 4.4-7.0),
coarse-grained soils that are poor in nutrients,
especially nitrogen and phosphorus. It rarely
develops where the annual rainfall is less than
400 mm per annum or where droughts are
common. In its adaptation to relatively infertile
soils, fynbos is analogous to the heathlands of
other Mediterranean regions.
The fynbos definition excludes renoster shrub
land - another evergreen, fine-leafed vegetation
type, dominated by the shrubby, granular-
leafed renosterbos, Elytropappus rhinocerotis
(Asteraceae), that once covered large tracts of
the more fertile clay soils of the coastal forelands
and intermontane valleys in the southwestern
Cape, but has now largely disappeared under the
plough. Renosterveld is especially rich in bulbs
but otherwise poor in typical fynbos plant groups
- most significantly proteas, ericas and restios
It replaces fynbos on richer soils with a higher
pH and a rainfall or around 600 mm per annum,
but both give way to karroid shrublands under
conditions of lower winter rainfall, around 250 -
300 mm per annum. With increasing summer
rainfall, fynbos is supplanted by other vegetation
types, including thicket, savanna and grassland,
except on nutrient-poor soils.
Fynbos is not strictly a Mediterranean
vegetation, in that it is not confined to regions
of winter rainfall. The real determinants of
fynbos vegetation appear to be limitations both
on growth and on the annual replacement of
leaves. These are most obviously the result of
an absolute shortage of nutrients in intrinsically
poor soils, such as the sandstones of the Cape
Fold Mountains. Nutrient deficiencies also occur
in richer soils where nutrients have either been
leached out of the surface layers by heavy rains
or are just not available to the plants for other
reasons, such as low temperatures or soil acidity.
This explains why patches of fynbos vegetation
occur on nutrient-poor soils in subtropical
southern KwaZulu-Natal, as well as on the highly
leached basalt soils in the high Drakensberg.
The dominance of fynbos in the southwestern
Cape, in both strictly Mediterranean as well as
temperate maritime climates, is primarily the
result of the extensive exposures of nutrient-poor
soils in the region.
Recognising fynbos
Fynbos is characteristcally a hard-leafed,
relatively open shrubland, about 1-3 m tall, often
with scattered taller bushes protruding above
the canopy. Fynbos shrubs vary greatly in height
and density but are mostly richly branched, with
twisted trunks. True trees are virtually absent. The
...
Fynbos diversity
Cape fynbos plant communities cover over
41 000 km2,or a little under half the total area
of the Cape Floristic Region, but are estimated
to contribute 70-80 per cent of the region's
flora, making fynbos easily the most diverse
vegetation type in this part of the world.
The entire Cape Floristic Region averages
94 unique species per 1 000 km2, making it
much more diverse than many other parts
of the world. California and southwestern
Australia, two other Mediterranean regions,
have respective average diversities of 14 and
just under 12 unique species per 1 000 km2 ,
and southern Africa as a whole averages just
8 unique species per 1 000 km2. Within the
Cape Floristic Region, fynbos alone may contain
between 150 and 170 unique species per
1 000 km2, an astonishing two or three times
that measured for tropical rainforests. How is
this extraordinary diversity possible? The secret
lies in the scale at which it is measured.
At the local scale, the number of species
occurring in a single plot of, say, one square
kilometre, can be counted and compared with
counts from similar plots in other vegetation
types.This gives us a measure of local diversity
(known technically as alpha diversity), which
averages around 65 species per km2 for Cape
fynbos.This is slightly lower than available
figures for renoster shrublands (84 species
per km2) but compares well with figures for
Australian kwongan heathlands; Californian
chaparral communities, at 30 species per km2,
are much less diverse. At this scale, tropical
rainforests are easily the most diverse habitats
on Earth, with a local richness ranging between
130 and 190 species per km2. On this basis,
fynbos, although diverse, is not extraordinarily
so. How then do we explain the enormous
diversity for the vegetation type as a whole?
Botanists have now established that the
main source of fynbos diversity lies not in
the absolute number of species found at any
particular site but in the proportion of species
that is shared between sites, either nearby but
with a different ecology, or distant and with a
similar ecology (measures known respectively as
beta and gamma diversity). Measured in this way,
the diversity of Cape fynbos is far higher than
other vegetation types -the result of the high
rate at which species give way to others across
environmental and geographical gradients. Put
another way,Cape fynbos is characterised by
exceptionally high numbers of highly localised
species - those that are restricted to a single,
small area, sometimes less than one square
kilometre. In sites that are as little as 25 km apart,
for instance, between half and two thirds of the
species have been replaced by different ones.
This is in sharp contrast to tropical forests, where
individual species are widely scattered,and is
one of the reasons it is so difficult to identify
fynbos species: each locality is likely to have a
large proportion of different species.
This fynbos characteristic was already
evident to the indefatigable Lady Anne
Barnard, wife of the Secretary to the First British
Administration of the Cape, soon after her
arrival. ln her diary entry for 10 October 1799,
she notes'... l was more than ever confirmed
in the opinion that a botanist here must live a
year or two in the country for he must be in
many places at once as the plains, the marshy or
dry soils, the tops of mountains or the gullies all
produce very different flowers from each other
in the same season'.
Quite why nutrient-poor soils should foster .
such a high diversity of species is not clear.
One suggestion is that even slightly differing
ratios of limiting soil nutrients constitute
14
microenvironments that are sufficiently different
to permit a greater variety of plant species to
occupy a given area than is the case in more
fertile soils, where minor differences in nutrient
ratios are not significant. While this is an attractive
explanation for the relatively high levels of local
diversity in fynbos, it does not explain the rapidity
with which many species give way to others over
short distances, or the high proportion of local
species. Certainly, the diversity of microclímates
that characterises the Cape Floristic Region as a
result of its varied topography, soils and rainfall
patterns is important in stimulating the evolution
of different species. The role of fire in disrupting
the succession of species and in providing
opportunities for different survival strategies must
also not be overlooked (see below). ln addition,
the particular distribution of nutrient-poor and
nutrient~richer soils relative to one another is
probably important in fostering the evolution of
new species. It is likely that one of the key factors
in the floristic diversity of the Cape is that bands
of these soils, each bearing their own distinctive
fynbos or renosterveld communities alternate
so regularly with one another. The relative
isolation of the deposits or outcrops of sandstone
within a surrounding sea of shale is likely to have
encouraged the evolution of different species on
each of the sandstone islands.
Fire and fynbos
Fynbos is a fire-adapted vegetation and evidence
suggests that, in the absence of regular fires,
all but the drier fynbos types would become
dominated by trees. fynbos can thus be viewed
as a fire-dependent vegetation type, along with
grasslands and savannas.
The infertility of fynbos soils means that the
recycling of soil nutrients is essential for fynbos
survival. Fire is the motor that drives this cycle,
and fires at appropriate intervals are not only
an integral, but also an essential part of fynbos
ecology. Fires are more common in fynbos than in
any of the other heathlands around the world. This
is a result of the extreme flammabilityof the dried,
often intricately branched shrubs and restioids,
and it is rare to find stands of fynbos vegetation
that are more than 20 years old. Fires rejuvenate
the vegetation by removing moribund growth
and recycling precious nutrients back into the soil.
They also remove the choking canopy that has
grown up during the intervening years, allowing ,
light to reach the soil surface.
...
15
...
The origins of fynbos
Although the appearance of the first flowering
plants dates back to around 150 million years
ago or more, their real flowering began about
90 million years ago, and it took another 10
million years before they began to dominate
the fossil pollen record. Until then, flowering
plants appear to have eked out an existence in
the understorey of temperate coniferous forests
and among the fields of ferns that covered the
Earth, where they were probably restricted to1
disturbed habitats.
Most of southern Africa until around 60
million years ago was blanketed by subtropical
forest, although there are sure to have been
pockets of arid-adapted vegetation in dry valleys
and on shallow soils. More recent pollen samples
from the West Coast and Cape Peninsula
corroborate the occurrence of distinctly
tropical vegetation here, including palms
and other tropical trees and shrubs, as recently
as 10 million years ago, and these warm,
humid conditions appear to have
extended into the central Karoo. However,
the discovery of fossil pollen of fynbos
families, such as restios, proteas and ericas,
from deposits in Namaqualand that
have been dated to between 71 and 64 million
years ago, indicates that these typical Cape
elements were already present at this early time,
probably as part of the forest itself.
Around 30 million years ago, the climate
in southern Africa became drier and more
seasonal as a result of the establishment of the
South Atlantic high-pressure cell, which drives
our modern climate. The evolution of corms
from rhizomes in the southern African members
of the Iris family, as an obvious adaptation
to seasonal climates, appears to date from
this time. Prior to this. the climate around
the world had been largely warm and humid.
The elevation of the central southern African
plateau around 10 million years ago and the
more or less concomitant establishment of the
Benguela Current along the West Coast further
increased the aridity in the western half of the
subcontinent and initiated the establishment
of present weather patterns in the subregion.
The development of the modern winter-rainfall
climate in southern Africa, which led to the
current expansion of fynbos vegetation, is
21
thus a relatively recent event dating back a
mere three to five million years. More recently,
the southern African climate has undergone
several modest oscillations coinciding with
the recurrent ice ages that devastated the
flora and fauna of the northern hemisphere.
Although relatively small, these oscillations
have been enough to push the boundary of
the winter-rainfall region far to the northwest
at times, most recently as 17 000-15 000 years
ago. This would have allowed temperate plant
communities such as fynbos to expand their
range considerably beyond their current limits.
Indirect dating of the start of the
diversification of the Cape lineages for which
sufficient data is available from DNA studies,
gives dates ranging from 18 million years ago
for Pelargonium to eight million years ago
for Phylica. This evidence, although scant,
suggests that climatic changes, especially
increasing aridity, were instrumental in the
evolution of fynbos. As for the ancestors of
fynbos, it would appear that several of the
earliest, dating to around 80 million years
ago, were drawn from groups that are shared
with Australasia. These include the Protea, Iris,
Restio and Geissoloma families. At this time,
Antarctica and Australia were still more or less
contiguous, forming a great southern landmass
that could well have been the ancestral home
of these families. Dispersal to southern Africa
across the nascent Indian Ocean would not
have posed the problems that it does today.
Other fynbos families, such as the Penaea and
Stilbe families, seem to have been derived
from lineages that originated in tropical Africa,
with only a few, such as Palmiet. having their
nearest relatives in South America. Many of the
Cape elements found today in the mountains
of tropical Africa appear to have migrated
northwards to their current location rather
than southwards from there, as was originally
postulated for the genus Protea. In summary,
therefore, there is no single source from which
the ancestors of Cape fynbos were drawn.
Much of the richness at the species level must
be of recent age, having evolved since the
establishment of the modern climate in the
past few million years, and arising in an 'orgy
of speciation' that was almost certainly assisted
by the periodic pulses that characterise our.
current climate.
22
Fynbos conservation
The high diversity of fynbos and the large number
of local endemics dramatically increase the danger
of extinction for a substantial proportion of its
plants. In general terms, small areas with a great
diversity of plant species are most likely to have the
greatest number of rare and endangered species.
This is a consequence of the high proportion of
very localised species in such regions. Fynbos is
especially vulnerable, and the Cape Peninsula is
a typical example, with 161 species of flowering
plants endemic, or restricted, to it.
Worldwide, around 10 per cent of all
plant species are rare or endangered. In the
southwestern Cape, where two thirds of the
species are endemic, nearly one-third are rare
or endangered. This amounts to more than
2 000 fynbos species.
The number of species threatened with
extinction in South Africa has risen dramatically
since the last survey of rare and threatened
plant species was completed in 1997. ln the
Protea family, for instance, the number of
threatened species has risen from 22 per cent to
60 per cent, or almost two-thirds of the species.
Similar trends are evident in other families.
The greatest threat to the plants of the
southwestern Cape is the transformation of
habitat for urban development, agriculture
and silviculture. While species from lowland
habitats are most threatened, the increasing
cultivation of crops such as rooibos is
putting pressure on upland species as well.
Urban sprawl around Cape Town has caused
the extinction of several species in recent
years. Another major threat to fynbos is the
encroachment of alien vegetation, especially
Australian wattles and hakea. Fires at too-
frequent intervals pose a threat to the local
survival of fynbos species that are unable to re-
establish under such a regime. Still others are
under threat from the collection of wild plants
for traditional medicinal use.
The responsibility for conservation rests
with the individual, and everyone can make
a difference. Join local interest groups
in your neighbourhood concerned with
conservation, or adopt and protect a small
site with threatened species on it. With so
many species surviving precariously on tiny
fragments, fynbos needs all the help it can
get to survive.
...
