<P> In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below 0 ° C are treated as 0 ° C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 and 3 ° C (34.7 and 37.4 ° F), Holdridge quantifies the climate as alpine . </P> <P> Because the habitat of alpine vegetation is subject to intense radiation, wind, cold, snow, and ice, it grows close to the ground and consists mainly of perennial grasses, sedges, and forbs . Perennial herbs (including grasses, sedges, and low woody or semi-woody shrubs) dominate the alpine landscape; they have much more root and rhizome biomass than that of shoots, leaves, and flowers . The roots and rhizomes not only function in water and nutrient absorption but also play a very important role in over-winter carbohydrate storage . Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems . Other common plant life - forms include prostrate shrubs, graminoids forming tussocks, cushion plants, and cryptogams, such as bryophytes and lichens . </P> <P> Relative to lower elevation areas in the same region, alpine regions have a high rate of endemism and a high diversity of plant species . This taxonomic diversity can be attributed to geographical isolation, climate changes, glaciation, microhabitat differentiation, and different histories of migration or evolution or both . These phenomena contribute to plant diversity by introducing new flora and favoring adaptations, both of new species and the dispersal of pre-existing species . </P> <P> Plants have adapted to the harsh alpine environment . Cushion plants, looking like ground - hugging clumps of moss, escape the strong winds blowing a few inches above them . Many flowering plants of the alpine tundra have dense hairs on stems and leaves to provide wind protection or red - colored pigments capable of converting the sun's light rays into heat . Some plants take two or more years to form flower buds, which survive the winter below the surface and then open and produce fruit with seeds in the few weeks of summer . </P>

The biome at the top of a very high mountain at the equator would be