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Tundra vegetation is composed of dwarf shrubs, sedges, grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline. The tundra soil is rich in nitrogen and phosphorus. [2]
Cladonia rangiferina often dominates the ground in boreal pine forests and open, low-alpine sites in a wide range of habitats, from humid, open forests, rocks and heaths. It grows on humus, or on soil over rock. It is mainly found in the taiga and the tundra. A specific biome in which this lichen is represented is the boreal forests of Canada. [14]
The shortest growing season is found at the northern taiga–tundra ecotone, where the northern taiga forest no longer can grow and the tundra dominates the landscape when the growing season is down to 50–70 days, [22] [23] and the 24-hr average of the warmest month of the year usually is 10 °C (50 °F) or less.
Compared to the tundra, boreal forest has a longer and warmer growing season and supports increased species diversity, canopy height, vegetation density, and biomass. Unlike the tundra, which is characterized by a lack of trees and tall vegetation, [ 45 ] boreal forests support a number of different tree species. [ 46 ]
Both plant species and animal species have become endangered. The Aleutian shield fern is a plant species that have been endangered due to caribou tramping and grazing, slumping from growing substrate, and human foot traffic. [9] Animal species that are endangered in the tundra include the Arctic fox, caribou, and polar bears.
Not only do conifer trees thrive in acidic soils, they actually make the soil more acidic. Acidic leaflitter (or needles) from conifers falls to the forest floor and the precipitation leaches the acids down into the soil. Other species that can tolerate the acidic soils of the taiga are lichens and mosses, yellow nutsedge, and water horsetail.
Plant communities in this vegetation zone are also known to include thickets that are mainly composed of shrubby or woody vegetation, including species from the genera Ilex, Ageratina, and Baccharis. Fragmented forests can appear in the subpáramo due to microclimatic or edaphic conditions, yet the more abrupt changes are generally due to ...
[15] There are three types of tundra: Arctic tundra, [16] alpine tundra, [16] and Antarctic tundra [17] In tundra, the vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some tundra. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or ...