Tundra vegetation is the hardy plant life adapted to the planet’s coldest biomes. These regions, largely devoid of trees, feature plants that must endure extreme cold, powerful winds, and short growing seasons. This article covers the types of flora that characterize the tundra, the strategies they employ to survive, and their significance within these ecosystems.
Defining Features of Tundra Ecosystems
The tundra biome is shaped by harsh environmental conditions, with a defining characteristic being permafrost. This is a layer of permanently frozen soil and gravel that lies just beneath the surface, acting as an impenetrable barrier for roots. This barrier prevents the establishment of deep-rooted plants like trees, so only a thin top layer of soil, the active layer, thaws during the summer for growth.
This environment experiences long, cold winters where temperatures can plummet to -50°C, and growing seasons are brief, lasting only 50 to 60 days. The tundra is also similar to a desert, receiving low annual precipitation of 150 to 250 mm. This water scarcity is compounded by strong, persistent winds that accelerate moisture loss from plants.
The soil also presents challenges, as cold temperatures slow the process of decomposition. This leads to a limited supply of available nutrients, with dead organic material serving as the main nutrient pool. The primary nutrients, nitrogen and phosphorus, are scarce; nitrogen is supplied through biological fixation and phosphorus through precipitation.
Predominant Plant Types in Tundra Regions
Mosses are a common sight, often forming extensive mats across the landscape. Species like Sphagnum moss are prevalent, contributing to peat formation and insulating the soil. Lichens are also abundant, with organisms like Reindeer moss (Cladonia rangiferina) and map lichens colonizing bare rock and soil where other plants cannot gain a foothold.
Grasses and sedges are common, forming tussocks that help them endure the cold and wind. Cottongrass (Eriophorum) is recognized by its fluffy white seed heads that dot the summer landscape. Tufted hairgrass (Deschampsia cespitosa) is another common species, and these plants provide an important food source for many tundra herbivores.
Dwarf shrubs survive by staying close to the ground, a strategy that protects them from harsh winds. Common species include dwarf birch (Betula nana), various willows (Salix species), and Labrador tea (Rhododendron tomentosum). These woody plants often have small, leathery leaves to minimize water loss, and Crowberry (Empetrum nigrum) is another common low-lying shrub.
Herbaceous flowering plants, or forbs, add seasonal color to the tundra. The Arctic poppy (Papaver radicatum) has cup-shaped flowers that track the sun to maximize heat absorption. Other examples include Mountain avens (Dryas octopetala) and the cushion plant Moss campion (Silene acaulis). Cushion plants grow in dense, low mounds, a form effective at trapping heat and sheltering the plant from wind.
Ingenious Survival Mechanisms of Tundra Flora
Tundra plants exhibit many adaptations to persist in an environment of extreme cold and short growth windows. A primary adaptation is their low-growth form, with plants growing in mats or clumps close to the ground. This protects them from high winds, allows them to absorb warmth radiated from the soil, and lets them be insulated by snow cover during winter.
To cope with the brief growing season, many tundra plants have rapid life cycles, allowing them to grow, flower, and set seed in just a few weeks. Many species are perennials, which allows them to store energy and resume growth quickly when conditions become favorable. Some evergreens can even begin photosynthesizing under the spring snow cover before it completely melts to get a head start on the season.
Other physiological adaptations include:
- Darkly pigmented leaves and stems that help absorb more solar radiation for warmth.
- Fine hairs on stems and leaves to trap heat and reduce water loss from drying winds.
- The ability to perform photosynthesis at very low temperatures and in low light intensities.
- Antifreeze-like compounds within cells to survive freezing temperatures.
- Asexual reproduction through runners and rhizomes, a reliable method when conditions are too harsh for flowering.
Regional Variations in Tundra Plant Communities
Tundra plant communities exhibit significant variations based on geography, with three main types: Arctic, Antarctic, and Alpine. The Arctic tundra, located in the far Northern Hemisphere, is the most extensive. It features vast, treeless plains dominated by low shrubs, sedges, grasses, mosses, and lichens, supporting around 1,700 plant species.
The Antarctic tundra has far less plant diversity due to its extreme cold and isolation. Found primarily on the Antarctic Peninsula and surrounding islands, its flora consists mainly of mosses, lichens, liverworts, and algae. Only two species of flowering plants are native to the continent: Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis).
Alpine tundra is found at high altitudes in mountain ranges across the globe, above the treeline. Unlike polar tundra, its soils are often better drained and the environment is subject to higher levels of ultraviolet radiation. The growing season can be longer, approximately 180 days, but nighttime temperatures still drop below freezing. Alpine flora includes many perennial grasses, sedges, and forbs, along with cushion plants suited to the rocky, high-wind conditions.
Ecological Contributions and Vulnerabilities of Tundra Vegetation
Tundra vegetation forms the foundation of its ecosystem, serving as the primary producers. These plants support herbivores like caribou, reindeer, lemmings, and Arctic hares, which in turn sustain predators like Arctic foxes. The low-lying shrubs and dense mats of moss and lichen also provide habitat and shelter for wildlife, protecting smaller animals from the elements and predators.
Beyond the food web, these plants contribute to soil development and stability. Their root systems bind the thin layer of active soil, preventing erosion from wind and water. In many tundra regions, the slow decomposition of plant matter, particularly Sphagnum moss, has led to the formation of vast peatlands. These soils are a global carbon sink, storing large amounts of carbon in the permafrost.
This vegetation is vulnerable to environmental changes. Rising global temperatures pose a threat by causing permafrost to thaw, which can damage plant roots, destabilize the ground, and release stored greenhouse gases. This release creates a feedback loop that accelerates warming. Tundra plants also have slow recovery rates, making them susceptible to physical disturbances from human activities like resource extraction and increased traffic.