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Tropical alpine-like vegetation is found in the Andes above the elevational limit of closed-canopy continuous forest and below the permanent snow-line. In Peru and southward this relatively dry altitudinal zone is known as "puna", although the wetter phases in northern Peru also are commonly distinguished as "jalca" (Weberbauer 1945) and near the border with Ecuador as "páramo" (Brack 1986). Because of ambiguity as to floristic boundaries and evaluation of human impacts on the Central Andean flora, this Data Sheet takes an inclusive view of Peruvian puna, including all habitats and vegetation types above 3300 m (see Map 69). The puna thus includes most of the departments Huancavelica, Ayacucho, Apurímac and Puno; large sections of Cajamarca, La Libertad, Ancash, Huánuco, Pasco, Junín, Lima, Ica, Arequipa and Cusco; and smaller portions of Lambayeque, Moquegua and Tacna. Map 69 and most of our discussion exclude the small area of páramo near the border with Ecuador in the northernmost portions of the departments of Piura and Cajamarca (cf. Luteyn 1992).
Puna is found in three geographic subregions in Peru. The main subregion is on the Western Cordillera of the Andes from c. 8°-18°S. This includes part of the Puno plateau and Lake Titicaca; the rest of both are in Bolivia. From 8° to 31°S (c. 2800 km), there is only one pass below 4000 m (Duellman 1979). Topographic relief of the Peruvian puna is moderate compared to the steep escarpments on the eastern and western slopes of the Andes. Most of the puna has a rolling topography, with a wide variety of substrate types and drainage classes. Much of the region is underlain by bedrock of Tertiary and Quaternary volcanics (Peñaherrera 1989). Active volcanoes are present in the south. The highest elevations are rocky, glacially modified horns, some with icecaps; the highest peak is Nevado Huascarán (6745 m).
The Eastern Cordillera is on average lower and narrower than the Western Cordillera and consequently has a smaller area of puna, which extends from c. 7°-15°S. Topography is relatively moderate between 3300-3800 m. Higher elevations are steep rocky cirques. Only in the south are peaks high enough to have icecaps; the highest is Nevado Salcantaya (6271 m). Bedrock is of metamorphized Precambrian and Palaeozoic sedimentary rock. Several deep valleys cut through the puna of the Eastern Cordillera, creating biogeographical barriers.
Northern Peru constitutes the third subregion. The puna (jalca) is quite fragmented among the high elevations of several relatively low mountain ranges. Bedrock is often of Cretaceous metamorphic and sedimentary rocks.
In general, there is great heterogeneity in puna substrates depending on the bedrock underneath. There are also great differences in drainage, with many resulting types of soils - from histosols in boggy sites to well-drained mollisols. Some areas, particularly in northern Peru, have deposits as much as 1 m deep of glacial loess. Glacial moraines and associated landforms are found in almost all of the puna (cf. Clapperton 1993). In cold and arid climatic cycles of the Pleistocene, much of the highlands above 4000 m at times was covered by ice and some glacial tongues descended below 3000 m.
The current climatic regimes apparently date back only several thousand years. The last major deglaciation began 12,000 years ago, and temperatures were apparently warmer than at present until c. 5000 years ago (Hansen, Wright and Bradbury 1984). Median annual temperatures range from c. 8°C at 3300 m to 0°C at snow-line. Temperature conditions are mostly constant during the year, but show considerable diurnal variation (Sarmiento 1986). Temperatures may reach below -2°C at night and between 10°-20°C during daylight. Near Lake Titicaca, the temperature and humidity extremes are moderated by the large lake.
The annual precipitation is widely variable, from c. 150 mm to over 1500 mm. Troll (1968) used the north-to-south decline in precipitation in the Central Andes and strong west-to-east increase in cloud cover and annual rainfall to recognize three types of puna in Peru. We designate them as (1) wet puna, in two major locations: along the Eastern Cordillera, where it is influenced by moist air uplifted from the Amazon Basin, and in northern Peru, where air masses come from both the Pacific Ocean and the Amazon Basin; (2) moist puna, found in most of Peru, particularly on the Western Cordillera; and (3) dry puna, to the south of 15°S on the Western Cordillera. The wet puna receives 800 mm to more than 1500 mm of annual precipitation; the moist puna receives 400-800 mm, and the dry puna less than 400 mm.
The drier phases of puna are very seasonal, with most (70-80%) of the precipitation falling during 4-5 months, usually between December and April. Even the wet to moist puna (jalca) of northern Peru has a pronounced dry season from May to September. Only the wet puna areas of the Eastern Cordillera that are directly exposed to cloud banks on the upper edges of the Amazon Basin are almost aseasonal, with just a short dry season in July or August.
The three types of puna correspond to at least 25 different Holdridge life zones (Tosi 1960; ONERN 1976). Relative air humidity is often less than 30%, except when fog is present. Puna plants (cf. Smith and Young 1987; Cabrera 1968) must have adaptations to resist or avoid desiccation. Plant growth also is cold-limited. Often temperatures drop to near or below freezing at night, particularly if there are no clouds. On cool days, species can continue to photosynthesize if their leaves are in protected microclimates, for example by being near the ground or protected by the plant's pubescence.
From 3300 m to c. 4200 m the predominant vegetation types of puna are grasslands (picture). Bunchgrasses of Calamagrostis, Festuca and Stipa form tussocks that can grow to occupy 0.25-0.75 m² in basal area and reach 1 m in height (if not burned or grazed). In the dry puna, Festuca orthophylla predominates. In wet puna on the Eastern Cordillera, several species of Cortaderia can be important. Spaces around the tussocks are often filled by a number of herbs, including non-tussock-forming grasses and sedges, prostrate or low-growing forbs, lichens, mosses, and ferns and their allies such as Jamesonia and Lycopodiella.
From 3300-3800 m it is common to find patches of Andean forest growing in sites protected from frost and fire. Genera frequently present as trees or shrubs include Baccharis, Berberis, Brachyotum, Chuquiraga, Clethra, Escallonia, Gynoxys, Miconia, Myrsine and Weinmannia. Sometimes Alnus acuminata can be found. From 3600 m to more than 4400 m, especially in the moist puna of the Western Cordillera, are forest patches dominated by Polylepis spp. Trees and shrubs of Gynoxys, Miconia, Myrsine and Ribes are also usually present. In the south, scrub dominated by Buddleja spp. may be present (Tovar-Serpa 1973).
Puna grasslands found in the proximity of these woodlands may be invaded by woody species, if they are not regularly grazed or burned. The frequency of natural fire regimes in Peruvian puna ecosystems is unknown. Generally people burn the puna grasslands every one to five years to renew forage for their livestock. Occasionally shrubs can be locally common in puna grasslands despite frequent burning; the shrubs are species of the microphyllous genera Baccharis, Diplostephium, Hypericum, Loricaria and Parastrephia.
Areas with poor drainage are usually dominated by sedges and rushes. Below 4000 m these genera include Carex, Juncus, Oreobolus and Scirpus. Above 4000 m, vegetation in the wet areas is dominated by floating and submerged cushion plants. Distichia muscoides and Plantago rigida are often conspicuous, forming large cushions. Other genera include Gentiana, Hypsela, Isoetes, Lilaeopsis, Ourisia, Oxychloe and Scirpus. Aquatic plants are common in ponds and streams, including Crassula venezuelensis, Myriophyllum quitense, Potamogeton spp., Ranunculus spp. and Zannichellia andina (León 1993).
Grasses begin to lose their dominance on well-drained substrates above c. 4200 m. The altitudinal zone of 4200-4800 m is what Weberbauer (1945) apparently considered typical puna. The predominant life forms are prostrate, cushion and rosette herbs of genera such as Azorella, Baccharis, Daucus, Draba, Echinopsis (Trichocereus), Gentiana, Geranium, Lupinus, Nototriche, Plettkea, Valeriana and Werneria . Elevations above 4800 m have vegetation types with these same taxa as dispersed individual plants. Often bare ground predominates, especially on scree slopes made unstable by needle-ice.
The dry puna is characterized by sparse vegetation and typically dominated by shrubs. Bunchgrasses and cushion plants are also present. Plant genera include Aciachne, Adesmia, Margyricarpus, Parastrephia and Tetraglochin.
Approximately 1000-1500 species comprise the vascular flora of Peru's puna. Many species are endemic to one or more of the puna's subregions, and many genera have their centres of diversity here, e.g. Culcitium, Perezia and Polylepis. Endemic genera include Alpaminia and Weberbauera (Brassicaceae) and Mniodes (Asteraceae) (Rivas-Martínez and Tovar-Serpa 1983).
About 10% of the flora is represented by pteridophytes. Conspicuous or speciose genera include Elaphoglossum, Jamesonia, Huperzia and Lycopodium. In wetlands and lakes, Isoetes spp. often are present.
Monocotyledons account for perhaps 30-40% of the flora. Grasses are very conspicuous, especially genera such as Agrostis, Calamagrostis, Festuca, Paspalum and Stipa, and in more humid areas Chusquea and Cortaderia. Also conspicuous are the sedges, such as Carex, Oreobolus and Scirpus; and the bromeliad Puya. Present, although usually inconspicuous, are orchids of the genera Aa, Odontoglossum, Pleurothallis, Pterichis and Trichoceros. Several species of Bomarea and Sisyrinchium are usually present. Excremis coarctata is common on the Eastern Cordillera (Young and León 1990), whereas several Orthrosanthus species are found on the Western Cordillera (Sagástegui-Alva 1988).
The dicotyledons are represented by more than 175 genera. Particularly diverse or conspicuous families include Asteraceae (Baccharis, Bidens, Culcitium, Chaptalia, Diplostephium, Gnaphalium, Hieracium, Liabum, Oritrophium, Senecio, Stevia, Werneria); Brassicaceae (Cardamine, Draba, Weberbauera); Campanulaceae (Lysipomia); Caryophyllaceae (Arenaria, Cerastium, Pycnophyllum); Rosaceae (Acaena, Alchemilla, Potentilla); Rubiaceae (Arcytophyllum, Galium); and Scrophulariaceae (Agalinis, Bartsia, Calceolaria).
Many of the herbs have adaptations to the cold: prostrate and rosette life forms, considerable pubescence and/or small leaves. Often they have surfaces that discourage grazing animals, such as prickles, spines or thorns on Chuquiraga, Opuntia and Puya. Plants that resprout after being grazed are also preadapted to survive repeated fires (Young and León 1991), which presumably explains the success of bunchgrasses in the Peruvian puna.
Native grasslands in Peru are used mainly for the grazing of cattle (picture), horses, sheep and South American camelids. More than 70 native fodder species are recognized in the puna; among the more important are Bromus spp., Calamagrostis spp., Festuca spp., Muhlenbergia spp., Nasella spp., Poa spp. and Stipa spp. (Ruiz-Canales and Tapia-Núñez 1987; Becker, Terrones-H. and Tapia 1989). Also consumed by the livestock are Alchemilla spp., Hypochoeris spp., Luzula spp. and Nototriche spp., and some aquatics such as Elodea potamogeton and Myriophyllum quitense.
The lower elevations of puna are often used for growing native and introduced crops. Native Andean crops include tubers, represented by several kinds of potatoes (Solanum acaule, S. andigenum, S. curtilobum, S. juzepczukii, S. tuberosum), "ollucos" (Ullucus tuberosus), "oca" (Oxalis tuberosa); and pseudo-cereals (Amaranthus caudatus, Chenopodium quinoa, C. pallidicaule). Other Andean species are planted in mixed fields with tubers and cereals. These species, such as Lupinus spp., Phaseolus spp. and Vicia spp., may represent a potential source for new commercial crops.
Besides traditional Andean crops, many native species are harvested for food as fruits, e.g. Ribes brachybotris and Salpichroa hirsuta, or as part of a dietary complement, such as the algae Nostoc spp. Some of the puna plants are used as spices (Hypochoeris, Tagetes). Medicinal plants from the puna are highly appreciated in Peru. Common medicinals include the pteridophytes Huperzia and Jamesonia, and dicotyledons such as Baccharis, Perezia, Tagetes (Asteraceae); Draba, Lepidium (Brassicaceae); Gentianella (Gentianaceae); and Lepechinia, Minthostachys, Salvia, Satureja (Lamiaceae).
Most of the highland residents use fuelwood for cooking and heating. Several species of shrubs are commonly exploited, including Baccharis tricuneata and Parastrephia lepidophylla (Reynel 1988). Species of Azorella are used for fuel in Arequipa's puna (Hodge 1948). In the central and northern part of the puna region, fuel sources include the cushion plant Distichia muscoides and the small trees Escallonia spp. and Kageneckia lanceolata. In the south, boats and houses are constructed using Scirpus californicus subsp. tatora.
Social and environmental values
The long experience of the Andean people in selecting and maintaining crops is the basis for their rich agricultural heritage. In addition, the puna is a genetic storehouse due to the presence of wild relatives of present-day and potential subsistence and commercial crops (Altieri, Anderson and Merrick 1987). However, because of social and economic conditions, many rural communities in or near the puna are being abandoned in favour of migration to the cities.
Land-use practises date from pre-Inca times (e.g. Schjellerup 1992). During the Inca empire terracing and irrigation were widely used below 4000 m, thus dramatically changing the landscape (Seibert 1983). Most of the puna supports intensive grazing. The highest elevations are mainly grazed by llamas and alpacas, whereas at lower elevations these animals share pastures with sheep, and to a lesser extent, cattle.
Tourism is limited to archaeological sites, with the partial exception of Huascarán National Park, which receives many hikers and alpinists.
Thirty-five bird species of restricted range occur in the woodlands of Polylepis, Weinmannia, Gynoxys and Escallonia and the puna vegetation throughout the Peruvian Andes. Two Endemic Bird Areas (EBAs) have been defined. Many of the species restricted to the patchy high-altitude woodlands and puna in the High Peruvian Andes EBA (B27) have very specific ecological requirements; due to the widespread degradation of this zone, no less than 15 of them are considered threatened. The Junín puna EBA (B28) covers two discrete areas of central Peru in a region that was ice-free during the last glaciation; five bird species are confined to the area around Lago (Chinchaycocha) de Junín (about 11°S, 76°30'W).
The puna of Peru is used by 4-6 million people, at least indirectly. Today, four large cities with a long history are located in the puna: Cajamarca, Cerro de Pasco, Cusco and Puno (Map 69). Puna is one of the critical resource zones for the rural people of the Central Andes (cf. Winterhalder and Thomas 1978). Scenery and archaeological or cultural attractions confer a high potential value for tourism. However, development of tourism in the region should be accompanied by improvement of living standards for the involved rural communities. Some native animals of the puna, such as the vicuña (Lama vicugna), represent a possibly sustainable resource.
Introduced crop species include barley (Hordeum vulgare), oats (Avena sativa), rye (Secale cereale), wheat (Triticum) and broad beans (Vicia faba). Introduced fodder species include Dactylis glomerata, Festuca pratensis, Lolium perenne, Medicago sativa, Phalaris tuberosa and Trifolium pratense (Ruiz-Canales and Tapia-Núñez 1987). Several introduced plants have become naturalized in lower elevations of puna. These include Brassica spp., Lolium perenne, Medicago spp. and Trifolium spp. Pennisetum clandestinum and Taraxacum officinale are among the worst weedy plants in the country.
The puna is one of the most heavily altered natural regions in Peru. The long history of human settlement goes back some 10,000 years. Recent social and economic conditions in the country have damaged preservation of genetic material of native Andean crops. Degradation of habitats at present is mostly related to overgrazing and contamination from mining.
Overgrazing increases soil erosion, especially in areas where drought has impacted in recent decades, as in the Department of Puno. Overgrazing has been related to cultural factors that cause over-stocking and to the lack of alternative sources for forage (e.g. Le Baron et al. 1979). Grassland burning associated with this grazing affects populations of native non-fodder plants, including for example the few existing stands of the giant bromeliad Puya raimondii (Cerrate de Ferreyra 1979).
Pollution by mining activities can be seen most clearly in water bodies and poorly drained areas. Aquatic and semi-aquatic vegetation is affected, thus threatening populations of geographically restricted plants, such as species of Isoetes (Young and León 1993).
The scarcity of fuelwood causes high pressure on the native vegetation: trees of Polylepis spp. and Buddleja spp. are cut for this purpose. Reforestation programmes have relied heavily on introduced species, mainly eucalypts (Eucalyptus), which has probably also adversely affected the local fauna and flora.
Puna is officially protected in three National Parks. The vegetation within Huascarán National Park (3400 km²) consists exclusively of puna (Smith 1988); the NP is the core of Huascarán Biosphere Reserve (3992 km²), which is recognized by UNESCO-MAB. There are 184 km² classified as puna in Río Abiseo NP (picture) and 796 km² in Manu NP. Other protected areas with puna include five National Reserves (Calipuy, Junín, Pampa Galeras, Salinas Aguada Blanca, Titicaca), three national sanctuaries (Huayllay, Calipuy, Ampay) and three historical sanctuaries (Chacramarca, Pampas de Ayacucho, part of Machu Picchu).
These designated areas total approximately 9500 km² of puna and represent c. 4% of the general area of puna, or just 0.7% of the area of Peru. However, actual protection of puna in these parks and reserves is sadly deficient; there is a lack of infrastructure and personnel. In addition, there has been no attempt to preserve pristine habitat types or restore them.
Outside of the reserved areas, there need to be many more programmes that seek to alleviate the causes of over-grazing and soil erosion. For example, environmental impact assessment and mitigation should be carried out for mining operations located in puna. Reforestation programmes should incorporate more native species and be directed toward appropriate fuel species.
Map 69. Peruvian Puna, Peru (CPD Site SA33)
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This Data Sheet was written by Dr Kenneth R. Young (University of Maryland Baltimore
County, Department of Geography, Baltimore, MD 21228, U.S.A.), Dra. Blanca León (Museo de
Historia Natural, Apartado 14-0434, Lima- 14, Peru) and Asunción Cano (Museo de Historia
Natural, Apartado 14-0434, Lima-14, Peru) and Olga Herrera-MacBryde (Smithsonian
Institution, SI/MAB Program, S. Dillon Ripley Center, Suite 3123, Washington, DC
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