<P> Alpine tundra does not contain trees because the climate and soils at high altitude block tree growth . Alpine tundra is distinguished from arctic tundra in that alpine tundra typically does not have permafrost, and alpine soils are generally better drained than arctic soils . Alpine tundra transitions to subalpine forests below the tree line; stunted forests occurring at the forest - tundra ecotone (the treeline) are known as Krummholz . </P> <P> Alpine tundra occurs in mountains worldwide . The flora of the alpine tundra is characterized by dwarf shrubs close to the ground . The cold climate of the alpine tundra is caused by the low air temperatures, and is similar to polar climate . </P> <P> Tundra climates ordinarily fit the Köppen climate classification ET, signifying a local climate in which at least one month has an average temperature high enough to melt snow (0 ° C (32 ° F)), but no month with an average temperature in excess of 10 ° C (50 ° F). The cold limit generally meets the EF climates of permanent ice and snows; the warm - summer limit generally corresponds with the poleward or altitudinal limit of trees, where they grade into the subarctic climates designated Dfd, Dwd and Dsd (extreme winters as in parts of Siberia), Dfc typical in Alaska, Canada, parts of Scandinavia, European Russia, and Western Siberia (cold winters with months of freezing), or even Cfc (no month colder than − 3 ° C (27 ° F) as in parts of Iceland and southernmost South America). Tundra climates as a rule are hostile to woody vegetation even where the winters are comparatively mild by polar standards, as in Iceland . </P> <P> Despite the potential diversity of climates in the ET category involving precipitation, extreme temperatures, and relative wet and dry seasons, this category is rarely subdivided . Rainfall and snowfall are generally slight due to the low vapor pressure of water in the chilly atmosphere, but as a rule potential evapotranspiration is extremely low, allowing soggy terrain of swamps and bogs even in places that get precipitation typical of deserts of lower and middle latitudes . The amount of native tundra biomass depends more on the local temperature than the amount of precipitation . </P>

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