Transcript Arctic and Alpine tundra environments

Arctic and Alpine tundra
environments
Flora and fauna
The biotic
environment
Vegetation
Plants that have adapted to live in very cold conditions, including changes in cell
structures when the temperature falls below freezing, are called hekistotherms. Many
plants also have to adapt to wet conditions, i.e. the bogs and muskegs of Northern
Canada and Siberia. These plants are hygrophytes, e.g. cotton grass or sedge. Those
plants which have to make do without much water because it is either frozen or there
are sandy conditions are xerophytes. In these plants small leaves limit the amount of
water lost through transpiration.
Therophytes are annual plants which
regenerate from seed. These are
absent.
Cryptophytes are adapted to extremes
of heat or cold and persist because they
regenerate from buds, bulbs or
rhizomes that are completely buried in
the soil.
Hemicryptophytes are typical of moist
temperate regions. They die back at the
end of the growing season and buds are
protected by the withered leaves and
soil.
Chamaephytes include small shrubs and
herbs that grow close to the ground.
Snow offers some protection during
cold winter months.
Phanerophytes are trees and small
shrubs. They carry buds on the tips of
branches. They are characteristic of hot
or mild moist environments where
plants are not subject to drought or
frost.
Types of plants found
in the tundra
Rhizomes
A usually elongate and branched modified plant stem which grows horizontally,
below or on the surface of the soil, often appears enlarged by food storage.
Roots, buds and leaves then emerges at different point from the nodes.
Rhizomes are creeping thickened stem (not a root) differ from other storage structures (like: tuber, bulbs,
etc.) by growing horizontally partially or entirely under the surface of the ground, consisting of a series of
nodes with roots. The primary growing point is at one end of the rhizome; additional growing points form
along its sides from the nodes.
Bloom plants
In the short Arctic summer the tundra
becomes a mass of colour. Arctic
poppies, gentians and saxifrage are
typical species.
Crowberry (Empetrum nigrum) above
Arctic foxglove below
Cotton grass (Eriophorum
angustifolium) on wetter ground
Anthocyany
Many of the flowers found
both in the Arctic tundra and
in the Alpine tundra are
coloured purple. In this way
they can absorb more of the
Sun’s energy and grow more
quickly. Such Alpine plants as
the gentian, saxifrage and
that on the right Hedysarum
hedysaroides all show bright
purples.
In the Arctic tundra many of
the heathers (Calluna) and
foxglove species have similar
colours. Such plants are
termed anthocyanic.
Many flowers such as arctic avens (Dryas
integrifolia) and arctic poppy (Papaver radicatum)
have bowl shaped flowers which act as parabolic
reflectors warming the plant. They are also
heliotropic and turn to face the sun as it moves
overhead.
Pollination
Pollination is chiefly achieved through
the help of insects, of which bees and
the ubiquitous mosquito are most
important.
Dwarf Birch (Betula nana)
A shrub layer of dwarf
willows and birches
develops where the
active layer is slightly
deeper. Usually they
grow to heights of 40
– 60 cm, but can
reach 2 – 5 m on
banks of rivers where
a deep snowpack
accumulates
protecting the plant in
the winter.
A much more diverse collection of plants occur
in Alpine tundra environments, partially due to
a wider variety of habitat. Crowberry
(Empetrum nigrum) is dominant at altitudes of
1600 – 2400m. Alpine grasslands are present in
wetter areas, with Alpine meadow grass (Poa
arctica) and mat grass (Nardus stricta) being
very common. They have long been used for
summer grazing. The grasses often form
tussocks and the dead grass helps protect the
living stalks.
Cushion plants such as musky saxifrage
(Saxifraga exerata) and Swiss rock jasmine
(Androsace helvetica) grow on ledges and in
crevices where there is more protection from
grazing and the weather.
Some Alpine plants are still to be found in
Snowdonia, e.g. Snowdon lily (Lloydia
serotina).
Alpine
mountain flora
Alpine meadow grass (Poa arctica)
Fauna
Lemmings
In the Arctic lemmings are the most
important species in terms of herbivory and
the subsequent transfer of energy to higher
consumers. They feed on grasses and sedges
in summer, but may include moss in winter.
Every 3 – 6 years the lemming population
increases sharply. Similar fluctuations occur in
other rodent populations in the Arctic, with
corresponding oscillations in predator species.
As lemmings consume the available food the
population crashes. Heavily grazed areas have
higher soil temperatures, which stimulates
decomposers to release more nutrients from
dead plant and animal tissue. Vegetation
recovers enabling the breeding success of
lemmings to improve. They reproduce 2-4 times
per year with 4-6 young per litter. This consumes
the available food supply and starvation sets in
with a further population crash.
Large
herbivores
of Arctic
tundra
Above left and right, reindeer – found in N Europe and Siberia
Below left, caribou – the N American equivalent Below right, musk ox
Large
herbivores of
Alpine
tundra areas
Above left – the chamois of the Alps
Below left – the tahr of the Himalayas
Above right – the llama of South America
Below right – the yak of the
Himalayas
Carnivores of the tundra
Carnivores are adapted
to the harsh conditions
with thick coats and a
hibernation period.
Arctic fox and
wolf
The importance of
lemmings is reflected
in similar oscillations
of many predator
species.
Brown
bear and
polar bear