DENSE or MIXED TUSSAC GRASS (Parodiochloa flabellata)
typically grows to a height of around 2 metres (although it can
reach 3 or 4 metres), and features a tussock-like growth form around
a fibrous pedestal. The pedestals accumulate slowly within a skirt
of dead leaves, and many of the larger specimens may be 200 or more
years of age. The pedestals provide nesting habitat for birds such
as magellanic penguins, thin-billed prions, sooty shearwaters and
small petrels, which burrow into or beneath it. The leaves, which
can grow up to 2 metres in length, bush out from the living crown,
and provide valuable nesting cover for passerines (eg. wrens, thrushes,
siskins), birds of prey (eg. striated caracara, turkey vulture,
short-eared owl), and coastal birds (eg. kelp geese, flightless
Tolerance or requirements for moist, salt-laden
air allows tussac grass to become dominant around coastal regions,
but more than about 300 metres from the coast, either lack of essential
requirements, or competitive exclusion, prevents tussac growth.
Therefore, with the exception of small islands of less than about
600 metres diameter, tussac tends to form a strip behind the coastal
zone. This natural pattern has been disrupted over the last couple
of hundred years by the introduction of livestock, and the sensitivity
of tussac grass to over-grazing.
Tussac grass can be split into two categories,
Dense Tussac where tussac is the dominant vegetation cover, and
Mixed Tussac where tussac is present in another plant community,
usually Oceanic Heath Formation (Grass or Dwarf Shrub).
Dense tussac grass modifies its own environment
in a number of ways. The leaf litter from tussac grass is slow to
decay, and forms a tussac peat, which can be deep, and high in nitrogen
and phosphorus. The association of tussac grass with nesting seabirds
and hauling-out sea mammals, helps to fertilise the ground with
droppings produced from food taken at sea, and provides a valuable
nutrient input to the tussac ecosystem. The dense leaf canopy which
can form an almost impenetrable growth, and the retention of dead
leaves around the pedestal, helps to insulate the tussac grass community
against extremes of temperature, and allows water retention. This
generates a sheltered micro-climate not only for nesting birds,
but also for invertebrates, which in turn provide food for birds,
along with the tussac seed. The closed canopy provides a hostile
environment for most higher plant species, leaving almost a monoculture
of tussac with just a few lower plant species and lichens capable
of growing in the poor light available. Amongst the higher plant
species which do seem adapted to surviving in tussac grass, are
sword grass (Carex trifida), wild celery (Apium graveolens) and
chickweed (Stellaria media).
GRASS HEATH is dominated by rough
grasses, usually whitegrass (Cortaderia pilosa), and covers the
largest areas of the Falklands mainland. The name whitegrass reflects
the fact that the growing point of the leaf is generally beneath
a longer dead leaf mass, giving the landscape a light buff appearance.
On fairly well drained sites it can adopt a tussock growth form,
and is often associated with pigvine (Gunnera magellanica), lawn
lobelia (Pratia repens) and chickweeds (Cerastium sp.). On poorly
drained plains, such as much of Lafonia, it takes on a more lax,
less tufted form, and tends to be associated with rushes, sedges,
astelia (Astelia pumila) and oreob (Oreobolus obtusangulus). Grass
heath supports many flowering plants, invertebrates and a few birds.
DWARF SHRUB HEATH is dominated by
low growing shrubs, particularly diddle-dee (Empetrum rubrum), and
tends to form on dry, well-drained areas, such as hard peat overlying
rocky ridges. It tends to be associated with tall fern (Blechnum
magellanicum), small fern (Blechnum penna-marina), mountain berry
(Pernettya pumila), teaberry (Myrteola nummularia) and christmas
bush (Baccharis magellanica). Dwarf shrub heath also provides shelter
for invertebrates, some smaller birds, and flowering plants such
as pale maiden (Sisyrinchium jubatum), scurvy grass (Oxalis enneaphylla),
vanilla daisy (Leuceria suaveolens), almond flower (Luzuriaga marginata),
violet (Viola maculata) and dog orchid (Codonorchis lessonii).
FELDMARK FORMATION is dominated by
cushion plants, such as balsam bog (Bolax gummifera) and cushion
plant (Azorella sp.), often in association with tall fern (Blechnum
magellanicum), small fern (B. penna-marina), dwarf shrubs and coarse
grasses. It tends to be found on higher hills and exposed ridges,
where the combination of thin shaley soils and exposure to wind
exclude faster growing species which lack adaptations to cope with
desiccation and nutrient deficiency. Although feldmark does provide
habitat for certain invertebrates and birds, the harsh conditions
and more open nature of this habitat means it generally lacks the
diversity of species found in other habitats such as tussac grass
or oceanic heath.
ROCKY OUTCROP The thin soils and
underlying geology result in many areas of exposed rock, either
as exposed bedrock, or surface stones such as stone runs. Such areas
provide nesting sites for certain birds such as ground tyrants,
red-backed buzzards, crested caracaras and peregrine falcons, and
can be colonised by lichens and specialist plants, such as snakeplant
FEN is an area surrounding ponds,
lakes or streams which features tall freshwater vegetation such
as willow herb (Epilobium ciliatum) and rushes (eg. Scirpus californicus
and Eleocharis melanostachys). Associated plants include marigold
(Caltha sagittata), water-milfoil (Myriophyllum elatinoides), starwort
(Callitriche antarctica) and blinks (Montia fontana). Fen is not
particularly abundant in the Falklands, although where it does occur
it is important as cover for nesting waterfowl, smaller passerines
BOG is a variable habitat type, usually
comprising wet swampy areas of short rushes or astelia (Astelia
pumila), often with low cushions of oreob (Oreobolus obtusangulus)
or patches of sphagnum. Associated plants include sundew (Drosera
uniflora), lawn lobelia (Pratia repens), lilaeopsis (Lilaeopsis
macloviana), blinks (Montia fontana), buttercup (Ranunculus trullifolius)
and pimpernel (Anagallis alternifolia).
FACHINE or BOX There are no
native trees, and only two native species which grow as bushes:
FACHINE (Chiliotrichum diffusum) and BOX (Hebe elliptica). Both
species are sensitive to grazing by livestock, and as such have
declined significantly since human settlement, now being virtually
absent from much of East and West Falkland. As well as supporting
a variety of invertebrates, such bush formations provide shelter
and nesting habitat for several passerines, such as thrushes and
SAND DUNES are areas of loose or
vegetated sand which form behind the littoral zone, and such habitat
is therefore generally restricted to coastal areas. The consolidating
vegetation can be sand grass (Ammophila arenaria), an introduced
species adapted to stabilising highly mobile sand, or other drought-tolerant
species more typical of grass and dwarf shrub heath. Such areas
can provide cover for nesting waders and other shorebirds, and may
well hold specialist invertebrates, although little work has been
conducted to determine this.
ERODED AREAS Such areas feature exposed
soil, as opposed to bedrock, and can be caused by overgrazing, burning
and physical disturbance. If the underlying soil is peaty, it can
be prone to drying out and blowing away, which can lead to a hollow
that may later be filled with water to create a temporary pond.
Such ponds are often devoid of higher lifeforms. Erosion is an increasing
problem, especially on coastal areas, and is usually, although not
always, a result of human activities.
SETTLEMENTS often provide niches
for various species of plants and animals, some of which are dependent
on human habitation (eg. House Sparrow). Other species such as the
black-chinned siskin and thrush, make use of habitats provided by
settlements in the form of planted shrubs and outbuildings. Rats
and mice, although able to survive away from settlements, favour
close proximity with man. Settlements also provide habitat for plant
species which can grow nowhere else. Trees and introduced shrubs
are often planted, along with numerous other garden plants, but
settlements can also provide refuge for native species which are
intolerant of grazing.
PASTURE is characterised by a short
turf of fine grasses, as opposed to the coarse grasses of grass
heath. These fine grasses provide a higher nutritional value for
grazing, but require a more fertile soil to out-compete the coarse
grasses which are adapted to thriving in poor soils. In the case
of pasture, these nutrients are provided by the droppings of livestock,
which tend to be kept at fairly high densities in such areas. Several
plant species with a tolerance of being grazed at ground level,
such as the daisy (Bellis perennis) and clovers (Trifolium sp.)
are associated with pasture, and the nitrogen fixing properties
of the clover will help maintain the nutrifying process. In general
pasture is too short to provide shelter or nesting habitat for birds,
and seems only to be of any real benefit to upland geese and lagomorphs
which graze on the nutritional grass species.
GREENS also consist of a short turf
of fine grasses, however the nutrient input does not come from livestock
but from a variety of natural processes. Coastal greens are often
associated with seabird colonies, where nutrients from food caught
at sea are deposited on land as guano, providing a major nutrient
input to the ecosystem. Similar associations may also result from
the presence of high concentrations of geese or lagomorphs. Alternatively
nutrient input may result from a topography which has a surrounding
catchment area, or from underlying soil or rock with a high mineral
content. Whatever the process involved, such areas tend to attract
grazing geese, which help maintain the green and keep it short.
The associated flora very much depends on the nature of the green,
but will predominantly be plants which are tolerant of being grazed
at ground level, such as those found in pasture.
TREES / GORSE There are no trees
or gorse native to the Falklands, although European Gorse (and some
tree species) have been planted at many settlements over the last
century as a living stock-proof fence, and for amenity and windbreaks.
Although they are introduced species, they can provide roosting
and nesting sites for some native species.
TEMPORARY or PERMANENT PONDS &
STREAMS The nature of ponds and streams varies enormously depending
on edaphic factors, topography, geology, surrounding vegetation,
weather patterns and farming practices. TEMPORARY ponds are subject
to drying out periodically, and can be merely muddy hollows, virtually
devoid of major lifeforms. PERMANENT ponds can provide a greater
stability for aquatic life, and some can be rich in flora and fauna.
Streams, and ponds connected to streams, may contain minnows (Galaxias
sp.) and sometimes the much rarer zebra trout (Aplochiton zebra).
Vegetation is likely to include water-milfoil (Myriophyllum elatinoides),
and around the margins there may be species such as marigold (Caltha
sagittata), starwort (Callitriche antarctica), blinks (Montia fontana),
spike rush (Eleocharis melanostachys) and native rush (Juncus scheuzerioides).
Ducks, geese and grebes are also likely to be found on the more
biologically diverse ponds. Invertebrates have not been examined
in any detail, but it is likely that certain species will have particular
associations with ponds and streams.
LITTORAL HABITAT TYPES
For the purposes of survey work, the littoral
habitat types are divided into the following basic categories.
a) Physical features:
Each section of shoreline can be categorised according to the ONE
definition which best describes its mean high water mark features.
- BOULDER SHORE consisting of stones
with an average diameter of more than 300mm. Boulders provide
cover for marine invertebrates avoiding desiccation at low tide,
and as such attract feeding birds such as black oystercatchers
and black-crowned night herons. Such coastlines are generally
subjected to high energy waves, and do not offer safe nesting
sites for birds, or suitable habitat for plants, except at the
very upper reaches of the shore.
- STONY SHORE consisting of stones
with an average diameter of between 2mm and 300mm. The shifting
nature of beach stones provides a poor substrate for plants to
gain a foothold, and little cover for fauna. Birds such as pied
oystercatchers, gulls and terns may nest on the upper reaches
of shingle beaches, but most other species prefer sites which
offer more seclusion. Elephant seals tend to choose shingle or
sandy beaches for breeding.
- SANDY SHORE consisting of visible
grains with an average diameter of less than 2mm. Sandy shores
can provide important feeding and nesting areas for breeding waders
such as pied oystercatchers and two-banded plovers, and feeding
grounds for visiting white-rumped sandpipers. Sandy shores are
also favoured by Gentoo and King penguins coming ashore to breeding
colonies further inland, as well as by gulls and terns which may
nest above the tide line. Plants such as sea cabbage (Senecio
candicans), thrift (Armeria macloviana) and sand grass (Ammophila
arenaria) are also often associated with the upper reaches of
sandy shores, which are frequently backed by a dune system forming
the transition into the terrestrial zone.
- MUDDY SHORE consisting of soft
sediment with grains too small to be visible with the naked eye.
Such sediments often provide a rich feeding area for waders such
as white-rumped sandpipers, because of the invertebrates living
in the mud. Low-energy, estuarine environments are usually covered
during spring tides, precluding nesting or the establishment of
- ROCKY SHORE of exposed bedrock.
The bedrock can provide secure attachment for marine invertebrates
such as mussels and limpets, and for marine algaes which in turn
support other marine creatures. Rockpools also tend to be numerous
at low tide, trapping small fish and marine creatures. This wealth
of marine creatures provides rich feeding for birds such as black
oystercatchers, black-crowned night herons and gulls. The high
energy waves prevent nesting, or the establishment of terrestrial
plants, except in the upper reaches where species such as native
crassula (Crassula moschata) may be found. Rocky shores are the
preferred breeding sites of fur seal and sea lion.
- CLIFF shoreline with steep slopes
that exceed 8m in height. The steep slopes and deeper water generally
make cliffs unsuitable for most birds as feeding or breeding areas.
Cliffs do however provide suitable nesting sites for rock shags,
rockhopper penguins, albatross and peregrine falcons which seek
out such sites. Birds such as black oystercatchers, kelp geese
and flightless steamer ducks can often be seen feeding along the
waters edge below the cliffs.
b) Biological features:
In addition to the physical nature of the shoreline, any number
of the following biological features may also be present. Despite
the fact that these are all essentially sub-littoral habitats, they
are included because of their importance as food resources for shorebirds.
- GREEN ALGAE Shoreline where green
algae such as sea lettuce (Ulva sp.) is found. Sea lettuce tends
to grow around the mean tide level, but also gets washed further
up shore, and provides a valuable food resource for birds such
as kelp geese.
- KELP BEDS Shoreline where kelps,
such as giant kelp (Macrocystis pyrifera) and tree kelp (Lessonia
sp.) can be seen growing in the waters above the lower shore zone.
Such marine habitats are important for many marine lifeforms.
- MUSSEL BEDS Shoreline where large
numbers of mussels are present. Mussels can be an important food
resource for oystercatchers and gulls, and in the late larval
stage for marine ducks.