Polylepis is a genus of trees and shrubs restricted to the Andes of South America. The genus belongs to the Rosaceae family and to the tribe Sanguisorbeae. It is wind-pollinated and can be recognized by its pinnate leaves and a multi-layered, papery bark, the latter feature also prompting its scientific name, a combination of Greek and Latin meaning "many-scales".
Polylepis species frequently occur at or above the natural tree line in the Andes.
Polylepis tarapacana is especially remarkable for being the woody plant occurring at the highest elevations worldwide. It forms monotypic stands at 3,800 - 4,500 m.a.s.l. , far above the natural treeline which is typically between 3,200-3,5000 m.a.s.l . These Polylepis forests are separated by the true treeline of the forests of the humid yungas or dry Interandean valles by shrubs or grasses of the puna.
Controversy exists between tropical ecologists whether its currently fragmented distribution is natural or the result of human land-use. Some scientists believe that much of the open grasslands of the Andean altiplano that currently separate isolated Polylepis forests were in fact one continuous forests before early native Andean peoples cleared or burned the ancient forests.
Polylepis forests exist primarily as small, widely isolated fragments, which are being rapidly depleted by rural communities. Remaining Polylepis forests are used for firewood and building material and provide protection against erosion and habitats for endangered animals. In some countries, conservation and reforestation measures are underway.
The genus has a complicated taxonomic history. Researchers have variously regarded it as comprising 15 to more than 30 species. The last treatment recognizes 28 speciesA N. Schmidt-Lebuhn, M Kumarb, M Kessler 2006. An assessment of the genetic population structure of two species ofPolylepis Ruiz & Pav. (Rosaceae) in the Chilean Andes. Flora 201,317.
Bitter, G. (1911). Revision der Gattung Polylepis. Botanische Jahrbucher fur Systematik, Pflanzengeschichte und Pflanzengeographie 45: 564-656.
Kessler, M. & A.N. Schmidt-Lebuhn (2006). Taxonomical and distributional notes on Polylepis (Rosaceae). Organisms, Diversity & Evolution 6: 67-69. Online supplement.
Simpson, B.B., 1979. A revision of the genus Polylepis . Smithsonian Contributions to Botany 43.
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