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S16 Tropical High Montane Scrub & Grassland Subclass
Type Concept Sentence: Tropical High Montane Scrub & Grassland is dominated by herbaceous perennials and small-leaved low woody shrubs or small sub-woody species in high tropical mountains, where freezing and cryogenic processes occur. It occurs in all tropical high mountains worldwide, where it occupies the sub-nival elevations.
Common (Translated Scientific) Name: Tropical High Montane Scrub & Grassland Subclass
Colloquial Name: Tropical High Montane Scrub & Grassland
Hierarchy Level: Subclass
Type Concept: Tropical High Montane Scrub & Grassland is dominated by herbaceous perennials and woody shrubs or small-leaved low sub-woody species in high tropical mountains, where freezing and cryogenic processes occur. It occurs in all tropical high mountains worldwide, where it occupies the sub-nival altitudinal belt. The predominant growth forms are rosulate plants with deep taproots and several plants with densely cespitose root systems and or creeping prostrate habit. The canopy cover varies from very low to open or semi-open. Species have, in general, adapted to sliding or movement of the substrate due to the diurnal alternation of freezing and melting, which is a typical phenomenon of the high tropical mountains. Soils have marked cryogenic phenomena, mainly contraction and expansion, gelifluction and freeze fracture (gelifraction).
Diagnostic Characteristics: Herbaceous perennials and small woody, small-leaved prostrate sub-shrubs, with a predominance of tap roots and creeping or densely cespitose root systems.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: The páramo and the dry and moist puna are not included in this subclass, because they have primarily mesomorphic adaptations, and because the soils are not subject to cryogenic processes. These vegetation types are treated with 2.A.2 ~Tropical Montane Grassland & Shrubland Formation (F017)$$. Nonetheless, although the páramo and the dry and moist puna are not subject to cryogenic soil processes, they are subject to varying levels of freezing. Perhaps the term "cryomorphic" places too great a restriction on the concept of "tropical alpine" vegetation.
Also challenging to place consistently in this class is the South American xerophytic vegetation of the Altiplano region of central and southern Bolivia, northern Argentina, and Chile, because the cryomorphic definition is very similar to xeromorphic; that is to say, they share ecological processes and have similar structures (growth forms) to each other. The vegetation is not Cool Semi-Desert, but is a hot/cold semi-desert, while at the same time is hardly affected by edaphic processes of cryoturbation and geliturbation expected of the cryomorphic class. We find again the diurnal rhythm of ice/thaw of the tropical mountains, but it is marked in these high dry southern areas with very high daily solar temperatures and very low nocturnal temperatures. For example, in the Great Salt Flats of Uyuni (Salar de Uyuni) to 3800 m of altitude, during the day temperatures can rise to 20°C and at night to -20°C. This is an extreme case related to the immense salt flats, but the lands that surround them repeat almost the same features listed above, although with smaller thermal amplitudes (C. Josse pers. comm. 2011). So high-elevation semi-deserts share some characteristics with the tropical high montane vegetation.
Also challenging to place consistently in this class is the South American xerophytic vegetation of the Altiplano region of central and southern Bolivia, northern Argentina, and Chile, because the cryomorphic definition is very similar to xeromorphic; that is to say, they share ecological processes and have similar structures (growth forms) to each other. The vegetation is not Cool Semi-Desert, but is a hot/cold semi-desert, while at the same time is hardly affected by edaphic processes of cryoturbation and geliturbation expected of the cryomorphic class. We find again the diurnal rhythm of ice/thaw of the tropical mountains, but it is marked in these high dry southern areas with very high daily solar temperatures and very low nocturnal temperatures. For example, in the Great Salt Flats of Uyuni (Salar de Uyuni) to 3800 m of altitude, during the day temperatures can rise to 20°C and at night to -20°C. This is an extreme case related to the immense salt flats, but the lands that surround them repeat almost the same features listed above, although with smaller thermal amplitudes (C. Josse pers. comm. 2011). So high-elevation semi-deserts share some characteristics with the tropical high montane vegetation.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Tropical High Montane Scrub & Grassland is dominated by herbaceous perennials and woody shrubs or small-leaved low sub-woody species in high tropical mountains, where freezing and cryogenic processes occur. The predominant growth forms are rosulate plants with deep taproots and several plants with densely cespitose root systems and or creeping prostrate habit. The canopy cover varies from very low to open or semi-open. It occurs in all tropical high mountains worldwide, where it occupies the sub-nival altitudinal belt. Species have, in general, adapted to sliding or movement of the substrate due to the diurnal alternation of freezing and melting, which is a typical phenomenon of the high tropical mountains.
Floristics: No Data Available
Dynamics: No Data Available
Environmental Description: Climate: Diurnal and nonseasonal energy pattern, with seasonal moisture regime consisting of a rainy summer and a dry winter that is a typical pattern of high tropical mountains, in contrast to non-tropical high mountains (temperate, boreal, Mediterranean) where there is a seasonal energy regime and where the rainfall has not matched up with the warmest time of year.
In the Andes, this formation is generally above 4500 m altitude.
Soil/substrate/hydrology: Soils have alterations in structure and texture due to deformation caused by freezing processes (contraction and dilatation) with diurnal periodicity of freezing and thawing. The substrates are mostly fine- to medium-textured, stony on the surface (loose stony pavement), with a muddy matrix that is saturated with meltwater and freezes daily. In tropical mountains, surface layers that freeze may overlie unfrozen subsurface layers. An important effect of frost-heaving is the upward movement of stones in soils and unconsolidated deposits that is more rapid and pervasive in wetter soils with a sparse vegetation cover. The process associated with frost can also cause upward or downward displacement of soil material in mass that can result in slope cryoplanation terraces at several scales. These soils are located in the highest areas of tropical mountains above 4500 m altitude.
In the Andes, this formation is generally above 4500 m altitude.
Soil/substrate/hydrology: Soils have alterations in structure and texture due to deformation caused by freezing processes (contraction and dilatation) with diurnal periodicity of freezing and thawing. The substrates are mostly fine- to medium-textured, stony on the surface (loose stony pavement), with a muddy matrix that is saturated with meltwater and freezes daily. In tropical mountains, surface layers that freeze may overlie unfrozen subsurface layers. An important effect of frost-heaving is the upward movement of stones in soils and unconsolidated deposits that is more rapid and pervasive in wetter soils with a sparse vegetation cover. The process associated with frost can also cause upward or downward displacement of soil material in mass that can result in slope cryoplanation terraces at several scales. These soils are located in the highest areas of tropical mountains above 4500 m altitude.
Geographic Range: This subclass occurs in tropical high montane regions of South America, eastern Africa, and New Guinea. Further review is needed to determine whether it occurs in Central America, Malaysia, and tropical oceanic islands. In the Neotropics, this type occupies the highest elevations of the tropical Andes, above 4500-4600 m altitude, from Venezuela to Argentina, and is well-represented in the central Andes of Bolivia and Perú.
Nations: No Data Available
States/Provinces: No Data Available
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.860231
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 4 Polar & High Montane Scrub, Grassland & Barrens Class | C04 | 4 |
| Subclass | 4.A Tropical High Montane Scrub & Grassland Subclass | S16 | 4.A |
| Formation | 4.A.1 Tropical High Montane Scrub & Grassland Formation | F022 | 4.A.1 |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: < Alpine semi-desert: biome-type 19 (Whittaker 1975) [Whittaker does not separate out tropical from temperate.]
< Tropical Alpine Biome (Quinn 2008) [Quinn includes both the tropical montane and tropical high montane scrub band grassland in her type.]
< Tropical Alpine Biome (Quinn 2008) [Quinn includes both the tropical montane and tropical high montane scrub band grassland in her type.]
- Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, C. Josse, A. Weakley, D. Tart, G. Navarro, B. Hoagland, S. Ponomarenko, J.-P. Saucier, G. Fults, and E. Helmer. 2015c. Classification and description of world formation types. General Technical Report RMRS-GTR-000. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO.
- Josse, Carmen. Personal communication. Senior Ecologist, Latin America. NatureServe, Arlington, VA.
- Quinn, J. A. 2008. Arctic and alpine biomes. Greenwood Press, Westport, CT.
- Whittaker, R. H. 1975. Communities and ecosystems. Second edition. Macmillan Publishing Co., New York. 387 pp.