Tundra

Tundra is a cold, largely treeless biome dominated by low-growing vegetation. Its soils often contain permafrost, a layer that remains frozen for at least two consecutive years.

Permafrost: Ground that remains at or below 0°C for at least two consecutive years. Its shallow seasonal thaw and long-term frozen layer constrain roots and water movement.
Arctic: The polar region surrounding the North Pole, including the Arctic Ocean and adjacent lands. Arctic tundra occupies much of the land within this broader region.
Arctic amplification: The phenomenon in which the Arctic warms faster than the global average. Rapid Arctic warming is transforming tundra temperatures, snow cover, and growing seasons.
Arctic tundra: Treeless ecosystems across the far northern regions of North America, Europe, and Asia. This is the characteristic polar form of tundra, shaped by long winters and permafrost.
Active layer: The surface layer of permafrost terrain that thaws during summer and refreezes in winter. This thin layer is where most tundra plant roots and soil activity occur.
Alpine tundra: Treeless ecosystems above the tree line on high mountains, with cold-adapted vegetation. It shares tundra conditions without depending on polar latitude or permafrost.
Permafrost carbon cycle: The movement and transformation of carbon stored in permafrost soils and released during thaw. Tundra soils hold large carbon stores that can become greenhouse-gas sources as they thaw.
Antarctic tundra: Sparse cold-adapted terrestrial ecosystems in ice-free parts of Antarctica and nearby islands. It shows that tundra-like vegetation occurs in the Southern Hemisphere as well.
Growing season: The part of a year when climatic conditions allow plants to grow. Its brevity limits tundra plant growth and favors species that flower and reproduce quickly.
Tree line: The boundary beyond which trees cannot grow because environmental conditions are too harsh. Tundra commonly begins where cold, wind, or a short growing season prevents tree growth.

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