trié(s) par (Pertinence décroissant(e), Titre croissant(e)) 

Environmental biology of a tropical treeline species, Polylepis sericea / G. Goldstein

Public in Tropical alpine environments : plant form and function / Philip Rundel (1994) Titre : Environmental biology of a tropical treeline species, Polylepis sericea Type de document : texte imprimé Auteurs : G. Goldstein, Auteur ; F.C. Meinzer, Auteur ; F. Rada, Auteur Importance : pp. 129-149 Langues : Anglais (eng) Résumé : "It is likely that Polylepis (Rosaceae) occurs naturally at higher elevations than any other arborescent angiosperm genus in the world. The 15 species (Simpson 1979) are confined to the South American Andes where they occur primarily in tropical alpine environments. Some Polylepis species tend to form discrete forest stands reaching elevations over 5000 m, well above the upper continuous forest limit (timberline). Throughout their high altitude distribution most members of this genus are exposed to rigorous climatic conditions in which diurnal temperature variations by far exceed seasonal ones and night frosts are frequent. The genus is exclusively arborescent (trees or shrubs), with individuals ranging in height from 1 m to no more than 30 m. The trees tend to have twisted, crooked stems and branches, particularly in open, exposed habitats. The form and branching pattern of some individuals resembles those of krummholz trees found in temperate alpine regions. The bark is deep red in color and consists of several layers of thin, exfoliating sheets. Although the exfoliating bark is particularly thick at the base of the stem or large branches, the insulating effect is by no means comparable to that of the marcescent leaves that surround the stem of the adjacent giant rosette plants (Smith 1979; Goldstein & Meinzer 1983). The leaves are compound and alternate but often appear whorled owing to the compression of internodes at the branch tips. The leaflets are small, dark green above and are covered with dense, silvery trichomes on the underside in several species." (source : auteurs) Type de publication : article de livre Référence biblio : Goldstein G., Meinzer F.-C., Rada F., 1994 - Environmental biology of a tropical treeline species, Polylepis sericea. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 129-149. ID PMB : 7614 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7614

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Pàramo microclimate and leaf thermal balance of Andean giant rosette plants / G. Goldstein

Public in Tropical alpine environments : plant form and function / Philip Rundel (1994) Titre : Pàramo microclimate and leaf thermal balance of Andean giant rosette plants Type de document : texte imprimé Auteurs : G. Goldstein, Auteur ; F. Rada, Auteur Importance : pp. 45-59 Langues : Anglais (eng) Résumé : "General climatic features of tropical alpine regions have been discussed in Chapter 1 of this volume. To reiterate, the nearly complete lack of temperature seasonality in tropical alpine zones is a key feature in distinguishing them from temperate alpine zones. The Andean páramo zone and similar zones in other tropical high mountains are characterized by high inputs of solar radiation in the presence of low inputs of thermal energy. This characteristic might be expected to present special circumstances from the standpoint of regulation of leaf thermal balance, in contrast to temperate alpine and desert habitats where both solar radiation and thermal energy inputs may be seasonally high. It has been suggested that some of the prominent morphological features found in giant rosette plants (see Chapter 1) represent adaptations for regulation of thermal balance under the special microclimatic conditions encountered in tropical mountains (Hedberg 1964; Larcher 1975). Numerous studies have dealt with the importance of characteristics such as leaf absorptance to solar radiation, leaf angle and rate of transpirational cooling as determinants of leaf temperature under a given set of environmental conditions (Mooney et al. 1977 Geller & Smith 1982). However, fewer studies have examined the interaction between spatial and temporal changes in environmental variables and plant features thought to be important for regulation of leaf thermal balance (Smith & Nobel 1977; Ehleringer & Mooney 1978)." (source : auteurs) Type de publication : article de livre Référence biblio : Goldstein G., Rada F., 1994 - Pàramo microclimate and leaf thermal balance of Andean giant rosette plants. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 45-59. ID PMB : 7617 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7617

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