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This project has been funded with support
from the European Commission.
Plants’ Adaptation To High
Altitude Environment
Students: Livia Murariu, Cristian Mazilu
Coordonating teacher: Cornelia Țăbârnac
Cuprins
1. Introduction
2. Air pressure
3. Air humidity and temperature
4. Soil temperature and humidity
5. Soil pH
6. Conclusions
Introduction
There are a number of factors that influence plants’ growth and
evolution on both short and long terms. This paper will, hopefully, clarify the
relation of these factors with the altitude that certain plants grow at. Considering
what instruments were available for our research and how much of an influence
certain factors had on the flora in the Bucegi National Park, we decided to study
the following physical, chemical, and biological characteristics of the
environment, as they evolve with the rising altitude of our trip:
•
Air pressure
•
Air temperature
•
Air humidity
•
Soil temperature
•
Soil humidity
•
Soil pH
In the following few pages, there will be information about each of these
environment characteristics, how they are influenced by altitude and how they
influence the vegetation. Moreover, information about our methods of
measurement will be provided, alongside possible sources of errors and how to
reduce their effects.
Air Pressure
Air pressure decreases as altitude increases,
due to the decrease of gravitational pull and the
amount of molecules above that push downwards.
This means a lower amount of air is available in the
same unit of volume, leading to less oxygen and less
carbon dioxide, substances that plants require in order
to survive. Moreover, a thinner atmosphere enforces
less resistance to ultraviolet light, which can damage
DNA, impair photosynthesis, damage cells membrane,
and thus decrease productivity.
One of the most consistent morphogenic
responses of plants to solar UVR (ultraviolet radiation)
is synthesis and accumulation of UV absorbing
compounds, such as a variety of phenolic substances
synthesised in vascular plants (like Fagus Sylvatica and
members of the Pinaceae or Betulaceae families)
some of which are found in the Bucegi National Park.
But storing these substances in the most vulnerable
parts of the plants, the leaves, means that they
needed to get thicker, also leading to a better
management of water and better resistance to
draught.
(1) The leaves of Fagus Sylvatica(both the European and American species); as
we can observe, the leaves are thicker and the European one is also ciliate, in
order to protect themselves from the UVR
Air humidity and temperature
Although vastly variable, both humidity and
temperature of the air, alongside wind currents,
determine what kind of precipitation falls in the
environment. First case scenario, let’s consider an
winter situation, where heavy snowfalls are frequent
and the thickness of the snow layer is significantly
larger than in lower altitude areas. This can cause a
heavy deposit of snow on trees branches, which,
assisted by wind, can lead to their inevitable break.
As a response, high altitude vegetation has
adapted to these conditions either by letting leaves
fall during the cold seasons, which allows the snow
to fall directly on the ground, or by engineering the
leaves in such a way that they allow for the snow to
fall past them. This is seen in plants like Abies, Larix,
Pinus, whose leaves are needle-like shaped,
decreasing the amount of snow that piles up on
them. Moreover, the flexibility of the branches and
the cone-like shape of the evergreens lets the snow
slide from branch to branch, until it hits the ground
(2) Larix – we can observe the shape of the branches, designed to
let the snow fall from them; the leaves are evergreen
Air humidity and precipitation are a rather
important factor to the amount of water in the
more rocky soil, further from groundwater. This
means that plants need to survive the droughty
periods of time frequent in the warm seasons.
One type of adaptation to this type of rocky,
draughty, cold environment is the plants’ growth in
so-called cushions.
A cushion plant is not a plant from any
particularly family or genus – cushion refers to the
growth form the plant takes. And species of plants
over a very wide range of groups (at least 30
families) have adapted this growth mode in cold,
short seasoned climates, in and around alpine
regions worldwide, as well as the arctic and
Antarctic (examples in Bucegi Natural Park:
Saxifraga oppositifolia, Silene acaulis,
Rhododendron kotschyi). If you get high up almost
any mountain range, both above and approaching
timberline, you will notice that many of the small
forbs you begin to see tend to grow very close to
each other in clumps. These clumps are usually
vaguely circular and often appear puffy, like a
pillow, though not more than a few inches above
the soil.
(3) Silene acaulis – they grow very close to each other, taking the shape
of a cushion; thus, they protect themselves from wind and cold
The benefits of a cushion-like growth form at high altitudes go beyond just heat retention and wind
protection – they also extend to increasing soil moisture and nutrition in the area beneath the cushion.
Cushion plants, like most alpine plants, have a large, deep taproot. Because alpine soils often drain
quickly and are poor in nutrients, a long root system is important for the plant to be able to reach enough
water and nutrition. Most alpine plants are perennial and die back to their roots in fall, having to exist on
stored resources throughout the 10 month dormant season, and a thick taproot can help with that. Some
research has shown that soil moisture in cushion sites can be increased up to 70% above non-cushion
sites, and available nitrogen up to 90%.
As the winds can get very powerful at high altitude, plants need very strong roots in order to avoid
being pushed down. These strong, deep roots are a common characteristic both in trees and in smaller
flora. Larix Decidua, Betula Pendula and Fagus Sylvatica have turning roots in the first few years of their
growth, followed by side roots that extend both sideways and downwards. Betula Pendula has a special
way of growing roots, by extending them sideways, where it forms adventive buds, from which a new set
of roots oriented downwards develops. Moreover, Fagus Sylvatica has adapted to merge its roots to with
the roots of nearby trees, to improve stability in windy situations.
Soil temperature and humidity
As soil has a much greater heat capacity, it stays
warmer during winter and colder during summer, so
plants have adapted to store water and nutritious
substances underground, where they are less likely to
freeze to death during winter, allowing them to survive
during the cold season, and to restart growing when
temperatures rise again.
A great example found in Bucegi National Park is
Aconitum Anthora, which has multiple underground
bulbs, protected from outside winter weather. These
organs also play the role of a back-up water source for
draughty times.
(4) Aconitum Anthora – its bulbs work as back-up
containers
Soil pH
The soil PH rarely affects plants growth, as
long as it stays in the normal range, which is
between 6.5 to 7.5, primarily neutral soil.
However, the alpine soil can reach PH values as
low as 4.5, which allow the Al3+ ion to dissolve,
intoxicating plant roots. It is beyond the reach of
this paper to explain the exact mechanism of Al
tolerance in certain plants, but it can be pointed
out that Phosphorus plays an important role in
plants’ resistance to Al.
Moreover, exudations of organic acid anions
from plant roots play a central role in Al tolerance
mechanisms. In Bucegi National Park, Saxifraga
Oppositifolia grows in acidic soils, the preferred
soil acidity for this plant ranging between 4.5 to
5.5.
(5) Saxifraga Oppositifolia – growing in an acidic soil
Conclusions
Plants needed to evolve a relatively large number of adaptations in order to survive in the harsh
environment of high elevation areas, the most notable obstacles being:
High levels of ultraviolet radiation
Heavy snow deposits on branches (for trees)
Draughty year periods
Rocky soils
Low temperatures
Strong winds
Low soil PH
In response, the main characteristics vegetation developed, in order to cope with these conditions are:
Production of phenols for UV protection
Thick leaves for better water management
Elastic branches for preventing snow from piling up
Growth in cushion-like groups
Deep, merged roots for better stability
Underground storage organs to prevent freezing
Production of special substances to prevent Aluminum intoxication
Thank you for your
attention! 