1. Plants’ Adaptation To High Altitude Environment
This project has been funded with support from the European Commission.
Students: Livia Murariu, Cristian Mazilu
Coordonating teacher: Cornelia Țăbârnac

2. Cuprins Introduction Air pressure Air humidity and temperature
Soil temperature and humidity
Soil pH
Conclusions

3. 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.

4. 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

5. 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

6. 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

7. 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.

8. 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

9. 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

10. 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

11. 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

12. Thank you for your attention! 