Plants are tough creations of nature. They will happily photosynthesize above 21,000 feet, but higher altitudes also create some challenges. From long-lasting snow blankets and intense solar radiation to howling winds and brutally low temperatures, plants face rigorous conditions at high elevations. Let’s learn more about how high altitude affects plants.
Light intensity
The intensity of light and radiation levels are stronger at higher altitudes because of a thinner atmosphere. Plants at high elevations also get more hours of sunlight as compared to lower altitudes. Combined with low air density and particulate matter, you get high solar radiation levels.
More exposure to sunlight generally increases photosynthesis and enhances plant growth. But the higher you go, the more protection your plants will need from the scorching sun. Ultraviolet rays can cause major tissue damage in plants. Some of the most intense UV-B exposure occurs in the spring, when there are fewer clouds, more direct sunlight, and plentiful snow that reflects the sun.
All this results in enhanced irradiance that is naturally countered by cloudiness and less atmospheric scattering higher up. In such environmental conditions, plants naturally evolve with adaptations like silver or lighter leaves that reflect the light. These leaves are thick and small to pack more ultraviolet-absorbing pigments such as flavonoids in the tissue.
Temperature
A high altitude means lots of wind, air movement, and low air pressure, which all results in a lower air temperature overall. The air is thin at high elevations – meaning fewer air molecules, and less movement that would otherwise create some warmth.
Generally, an optimum temperature for plant growth is somewhere between 10-25 ℃. The higher the temperature within this range, the faster your plants will grow, provided that they’re getting nutrients, good light, and appropriate water and carbon dioxide levels.
Most plants require a certain temperature to grow at their best, but some adapt to colder temperatures at higher altitudes. Hardy subalpine conifers, for example, are capable of surviving brutally low, subzero temperatures.
High-country temperatures can get extremely cold, especially in middle and high latitudes during winter. Colder air and colder soil slow plant growth. Some plants even stop growing altogether in the winter. The low temperature and drier winds at high altitudes also lead to a short growing season.
During winters, moisture in the soil freezes and robs exposed leaves of moisture, causing excessive drying. Most confiners protect themselves from drying with reduced stomata, the organs responsible for transferring air and water across the leaf, and their waxy coatings. Deciduous species including larches and birches also effectively shut down during cold seasons to survive.
For example, the taiga ecosystem in arctic latitudes produces hardy taiga biome plants that show numerous adaptations for the ferocious subarctic climate.
Air pressure
Higher elevations always experience lower air pressure. This lowered air pressure can influence plant life in many ways:
- Plants need carbon dioxide to grow, and lower air density and atmospheric pressure at high altitude produces lower carbon dioxide levels and a slower transpiration rate
- Slow transpiration and limited carbon dioxide slow down the rate of photosynthesis and growth
- Ultimately, air pressure will also affect the size and quality of plants growing in high elevations
Wind
Most high-elevation areas, especially mountains, experience high wind speeds compared to lower elevations. These high-altitude winds never slow down because there is less tall vegetation to break it up. This wind has a number of effects on plants.
- High-speed wind breaks branches and stems, increases evaporation, and batters plants with windborne grit.
- Plants speed up or slow down their transpiration rates depending on how humid the air is. In windy conditions, the humidity level decreases, and plants lose water faster. This causes moisture stress, particularly on higher-latitude mountains in winters when frozen soil won’t let plants replace lost water via their roots.
- The wind makes plants stocky. They develop stronger, shorter stems and trunks due to increased rocking. Trees on windswept areas or slopes tend to show a “flagging” effect where they grow longer and denser leeward boughs and sparse, stubby growth on the windward side.
- Some plants, such as the alpine plants, have evolved with leaf hair that protects them from wind by keeping humidity around the leaf.
Drainage
Good drainage is important for most plants. And gardening up high means water easily runs downhill as you’ll likely always be on a slope. But this generous drainage system can also cause problems in the summer, when the soil dries out quicker than it should and absorbs or holds a very low amount of water for the plants.
Less water slows plant growth and decreases the quality of plant life. If you’re maintaining a garden in a high-altitude area, you’ll need sufficient supplemental water to keep your plants healthy and happy.
Oxygen levels
High altitudes mean lower atmospheric oxygen levels, which affects root growth. A healthy root system needs oxygen for aerobic respiration, a process that breaks down food into packs of energy for the plant.
A study at the University of Nottingham states that plants are adapting to altitude by “sensing” oxygen levels. This evolution has led them to control the chlorophyll synthesis pathway and match it with the surrounding oxygen levels. These genetic changes will save plants as climate change and global warming advance.
Precipitation
High altitudes receive more precipitation than lower elevations. Cold air doesn’t retain moisture well, so it releases the moisture as rain.
Another important factor that influences precipitation at high elevations is the orographic effect. It’s a process where mountains and hills practically induce precipitation when air directed upward by terrain is cooled to its condensation point. This results in increased cloud formation and precipitation.
High precipitation can actually help vegetation grow better, lusher, and denser. You might not even have to water your plants since the water coming from higher up the hill and retained in the ground due to continuous precipitation will keep your plants happy.
Plants in high altitudes also get a lot of dew in the mornings as the water around creates a highly humid environment. Plants go through a process called guttation where they release excess water from their leaves, which adds to the humidity levels.
Snowpacks
Snow lasts longer in high, mountainous mid- and high-latitude regions than it does in the lowlands. Snowpacks can both be good and bad for plants.
Pros of high-elevation snow include:
- It insulates and protects low tree branches, shrubs, and saplings from severe winter temperatures and unkind, drying winds.
- When the snow melts off in the spring and summer, it offers plenty of much-needed moisture to the plants below. This results in thicker, lusher vegetation and the overall health of plants.
Cons of snowpacks in high altitude areas:
- Snowfields linger well into late spring and early summer (or maybe longer). This prolongs the inactive period for plants and may result in weaker roots.
- Persistent snowdrifts and snowpacks limit the growing season in locations and keep most plant species from achieving a foothold.
Nutrient availability
Low temperature at high altitudes limits plant growth and nutrient supply. Plants are unable to absorb the required amount of nutrients for growth.
Nutrient content tends to significantly decrease with increasing elevation. A statistical analysis of over 150 plant species from all major climatic zones revealed the presence of Kjeldahl nitrogen in all of them, K, Mn, Mg, and Ca only in the Alps, and phosphorus in half of the samples.
FAQ
A: High altitude is considered 4,900 to 11,000 feet above sea level.
Three of the main things to know about gardening at high altitudes are to A) know the length of your growing season, B) choose plants that thrive in cooler, windier conditions, and C) start plants from seedlings indoors to give them a chance to establish.
If you’re setting up a garden someplace high, always trust our lawn love pros to assist you with all your gardening and maintenance needs.
Main photo credit: Wikimedia | CC-BY-4.0
