Central Andean Puna (general)
UNESCO described the puna as an entire phytogeographical area comprising the vegetation of both the altiplano and the neighbouring mountain slopes. It is general described as dry highland vegetation of the Central Andes, while its northern counterpart, the paramo, is generally regarded as wet highland vegetation of the Northern Andes. Nevertheless, puna can still be broadly divided into dry, moist and wet puna. Grasses such as Deyeuxia, Festuca and Poa typically dominate, with prevalence in the dryer areas of Festuca orthophylla and several species of Stipa. Low standing grasses of Muhlenbergia and Distichlis humilis together with halophytic shrubs cover much of the extended salt plains, while local fresh water cushion peat bogs or fens (bofedales or ciénagas) are dominated by the plant families Juncaceae, Cyperaceae and Asteraceae. Few trees besides Polylepis and Buddleja are present today.
Central Andean Dry or Tola Heath Puna
Found at elevation ranging from 3,500-5,000 m, the rainfall in these zones is very seasonal with dry seasons lasting up to eight months. This unique vegetation extends from the Peruvian Western Cordillera crossing the central altiplano in northern Bolivia and then gets restricted to the eastern edge of the altiplano in southern Bolivia. The sparse vegetation is typically dominated by shrubs up to 1 m high often characterized by tola (Parastrephia lepidophylla), but there are also small stands of Polylepis, the only arborescent genus that occurs naturally at these high elevations. Vast areas are also covered by bunch grasses, typically dominated by Festuca orthophylla especially in the slightly wetter areas, and cushion plants may also be present. Other typical plant genera include Aciachne, Adesmia, Margyricarpus and Tetraglochin, and there are various species of Andean camelids. All of the flora and fauna are highly adapted to the extreme conditions.
Central Andean Moist Puna
This seems to be synonymous with humid or grass puna, which covers vast areas from central Peru, where it spans the entire width of the Andes, to the central parts of the Bolivian altiplano where it is confined to a northerly exposed zone adjacent to montane forest. The zone widens again near Santa Cruz but then gradually disappears north of Tarija. The vegetation has well developed ground cover and largely consists of tussock grasses of the genera Calamagrostis, Festuca and Stipa. In between the tussocks are various delicate grasses and herbs. Also present are various rosette plants and cushion plants of the genera Azorella, Aciachne, Distichia, Plantago and the endemic Pycnophyllum (Caryophyllaceae). Cacti are generally rare but large cushion of the wooly Tephrocactus lagopus and T. floccosus can be conspicuous. Around the margins of Lake Titicaca, the humid puna is characterized tussocks of Stipa Ichu and Festuca together with various species of Baccharis, while the mountainous hinterland includes low bushes of Adesmia miraflorensis, Calceolaria parvifolia, Mutisia orbignyana, Satureja boliviana, Tetraglochin cristatum and several species of Senecio.
Central Andean Wet Puna
Wet puna is mainly found in northern Peru, where it is influenced by moist air from both the Amazon Basin and the Pacific Ocean, and along the Eastern Cordillera, where most of the moist air comes from the Amazon Basin. On the altiplano it occurs at elevations ranging from 3,700 to 4,200 m. On the Eastern Cordillera the vegetation is characterized by several species of Cortaderia. Between the tussocks there are often other grasses, sedges and low-growing forbs, together with ferns such as Jamesonia and lycopods such as Lycopodiella. Mosses and lichens are also common.
Central Andean Cushion Plant Formations
At high elevations over 4,000 m, cushion bogs or bofedales can be found with floating and submerged cushion plants (see below). The larger cushion plants include Distichia muscoides, Oxychloe andina and Plantago rigida, while other genera include Gentiana, Hypsela, Isoetes, Lilaeopsis, Ourisia, and Scirpus. In the less wet areas other cushion plant species occur such as the endemic Azorella compacta (Araliaceae) and Werneria aretioides (Asteraceae). In fact, Azorella compacta extends over vast areas between 4600-5200 m particularly on exposed slopes covered by rocky outcrops.
Central Andean Peat Bogs (Bofedales)
Peat is basically the remains of partially decayed plant material that accumulates in waterlogged situations. It is prevented from decaying fully by acidic and anaerobic conditions. However, peat bog are mainly associated with the more humid parts of the world, so it is rather strange that they occur here in one of the most arid parts of the world just east of the Atacama desert. It seems that groundwater is the prominent source of water and they generally lie in the bottoms of narrow, glacially modified alpine valleys or alpine basins at altitudes ranging from 3200-5000 m. Not surprisingly the vegetation of these remarkable peat bogs stands out in marked contrast to the surrounding vegetation. Much of it is composed of compact cushion plant formations (see above) mainly Oxychloe andina and Patosia clandestina while grasses such as Distichia filamentosa and D. muscoides dominate the ‘lawn’ and hummock formations. Sphagnum moss is also characteristic especially in northern peatlands. Wet peripheral areas typically include Deschampsia caespitosa, Deyeuxia velutina together with various species of Carex and Eleocharis.
Aquatic Vegetation
In the Nevado Coropuna volcano area of southern Peru the aquatic vegetation often includes Azolla filiculoides and Ranunculus limoselloides, while the marshy areas typically include Distichia muscoides, Lilaeopsis macloviana, species of Carex and the endemic Werneria pygmaea (Asteraceae). Characteristic of the drier marsh margins are Calamagrostis ovata together with species of Astragalus and Lupinus. The aquatic vegetation of Lake Titicaca is characterized by Elodea potamogeton Juncus arcticus subsp andicola, Myriophyllum quitensis and Schoenoplectus californicus subsp. tatora. Growing in the shallow margins of high-Andean lakes in the centre-north of the eastern ranges of Bolivia are swards characterized by Lachemilla diplophylla and Lilaeopsis macloviana. These areas often become completely dry towards the end of the dry season. Other species here include Alopecurus hitchcockii, Cotula mexicana, Deyeuxia jamesonii, Distichia muscoides, Oritrophium limnophilum and Plantago tubulosa.
Central Andean Shrubland Steppe
From east to west the vegetation gradually changes from shrubland steppe with xerophilous shrubs such as Adesmia, Baccharis, Fabiana, and Senecio to grassy steppe with grasses of the genera Calamogrostis, Festuca, and Stipa.Some of the common shrubs are Baccharis incarum, B. boliviensis, Parastrephila lepidophylla and Fabiana densa. These can reach heights of up to 2.5 m. On the Nevado Coropuna volcano in southern Peru there are stands of shrubby vegetation characterised by Mutisia acuminata (Asteraceae), together with species of Fabaceae and Solanaceae. Associated species include various endemics such as Chersodoma arequipensis, Diplostephium tacorense (Asteraceae) and Opuntia corotilla (Cactaceae).
Central Andean Polylepis Forest
Polylepis (Rosaceae) is only found in the South American Andes, and represents the characteristic taxa of the highest forests in the world. Twenty species of Polylepis are trees or shrubs and typically have a very gnarled appearance. The foliage is evergreen with dense, small leaves, and most of the species are exposed to harsh climatic conditions. They belong to the tribe Sanguisorbae, which mainly include herbs and small shrubs, and unique in the rose family in having a tendency towards wind pollination. The most primitive species, including Polylepis lanuginosa, P. multijuga and P. pauta, found in the Ceja se selva (Yungas) forest share traits with the genus Acaena (see the Chacoan BioProvince)..
In the Central Andes, unique forests of Polylepis tomentella and P. tarapacana are found, for example, around the Sajama Volcano at 5000 m above sea level in Bolivia, and there are stands of Polylepis tomentella in the puna belt of the Laguna de Pozuelos Biosphere Reserve in northwest Argentina, while Polylepis besseri (= P. rugulosa) is the main species found on the southern slopes of the Nevado Coropuna volcano in southern Peru. Most forests are encountered at altitudes ranging from about 3700-4600 m and seem to generally occur where there are high incidences of fog or cloud cover or in river gorges. However, in some places they can cover entire slopes where there are no particularly favourable environmental conditions. The trees are often festooned with mosses, vines such as Bomarea, Loasa, Mutisia, and Passiflora, mistletoes (Tristerix) and many epiphytic flowering plants. At ground level, often between moss-covered rocks, there is often a rich herbaceous flora, which on deep soils may include various nitrophilous plants like Cajophora and Urtica and several species of wild potatoes (Solanum). In the more arid stands, however, the undergrowth often hardly differs from the surrounding steppe or semi desert. On the Nevado Coropuna volcano, for example, the undergrowth is characterised by species Baccharis, Chuquiraga, Parastrephia (Asteraceae), Astragalus, Lupinus (Fabaceae) and various cacti. Other species often associated with these high-Andean Polylepis forests include Berberis chrysacantha, Berberis communtata, Berberis rariflora, Bomarea dulcis, Citharexylum punctatum, Colletia spinosissima, Dunalia brachyacantha, Fuchsia apatala, Gynoxis asterotrichia, Ribes brachybotrys, Satureja boliviana and Schinus microphyllus.
Central Andean Saltmarsh
These halophytic or salt-loving communities are mainly found in areas close to salt flats. Some of the typical species include Atriplex atacamensis, Distichlis humilis, Muhlenbergia fastigiata, Parastrephia lucida, Salicornia pulvinata, Senecio pampae, Suaeda foliosa, Tessaria absintoides and Triglochin maritima. On the Uyuni salt flats there are ‘islands’ of low salinity supporting cacti of the genus Oreocereus. In the Lake Titicaca area the saline vegetation has been described as halophytic prairie with stands occurring in both dry and humid puna - examples can be found adjacent to the Desaguadero River. Characteristic species include Anthobryum triandrum, Distichlis humilis, Muhlenbergia fastigiata, Parastrephia lucida, Salicornia pulvinata, Suaeda fruticosa var crassifolia and Triglochin maritima.
Central Andean High Altitude Formations
Above the puna region, at altitudes between about 4200 m and the highest limit of vegetation, grows sparse communities dominated by a few grasses such as Deyeuxia, Poa, together with endemics such as Anthochloa lepidula, Dielsiochloa floribunda, Dissanthelium calycinum, D. trollii and D. macusaniense and a large number of cushion plants, rosette and dwarf shrubs (Azorella, Xenophyllum and the endemic Pycnophyllum, Nototriche, and Werneria,). At slightly lower altitudes denser grass swards develop with Agrostis, Deyeuxia (e.g Deyeuxia minima), Poa and Stipa. Associated taxa include Luzula racemosa, species of Gentianella and Trichophorum and the endemic Oreobolopsis tepalifera (Cyperaceae), together with various perennial herbs. Most common plant families include Asteraceae, Caryophyllaceae, Geraniaceae and Malvaceae.
Further information required (especially regarding endemic plants).
References
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