Northern Andean Vegetation

Plant Formations in the Northern Andean BioProvince

Peter Martin Rhind

Northern Andean Páramo (general) Although páramo is generally described as high-altitude, wet tropical grassland above the tree line in the Andes of Venezuela, Colombia, Ecuador and northern Peru, it is extremely rich in biodiversity and contains a high level of endemism. One of the most distinctive features is the giant rosette of the Espeletia endemic complex. This includes over 100 species that belong to the sunflower family (Asteraceae). These plants are found only at high elevations of the northern Andes Mountains of Venezuela, Colombia and Ecuador. The centre of diversity is the Venezuelan Andes, while the eastern cordillera of Colombia also has a large number of species. The range of the complex extends from the coastal Caribbean mountains of Venezuela, north along the Sierra de Perijá to the Sierra Nevada de Santa Marta of Colombia, and south into northern Ecuador. The southernmost extent of the range is a disjunct population in an isolated páramo of central Ecuador known as the Serranía de Llanganates. Originally these were all classed as members of the genus Espeletia but this was elevated to a sub tribe, the Espeletiinae, and the species separated into eight separate genera, including Espeletia, Coespeletia, Espeletiopsis, Ruilopezia, Libanothamnus, Tamania, Carramboa and Paramiflos. Recent molecular studies, however, suggest that at least some of these genera may not be natural (monophyletic) groups. Many are characterized by an unbranched stem, often covered in a thick layer of dead leaves, topped by a rosette of spirally arranged, wooly leaves. Unlike most plants in the páramo, which tend to be short grasses, small herbs and shrubs, the giant rosettes of the Espeletia complex can grow to 5 meters tall and live for more than 100 years. Many of the morphological and physiological traits are thought to be adaptations to the harsh tropical montane climate. The spiral arrangement leaves and their dense layer of hairs together with the retained dead leaves help to provide both thermal insulation and protection against UV radiation. Of considerable interest, however, is the fact that the giant rosette growth form has evolved independently in plants from a variety of similar habitats across the world, with Espeletias being comparable with the silverswords of Hawaii and giant senecios and lobelias of Africa. This provides compelling evidence that this growth form is an adaptation to tropical montane conditions. In addition to the giant rosette, the evolutionary radiation of the Espeletia complex has resulted in a remarkable diversity of morphological forms, ecological specializations and life history traits. Species are found from the montane forests at about 2800 m, to the edge of the glaciers at 4600 m, and have adapted to a wide range of environmental conditions, from steep talus slopes and xeric rock outcrops, to wet marshes and bogs. Growth forms range from tiny, mat-forming sessile rosettes less than 5 cm tall, to giant rosettes, to branched shrubs and even large trees over 15 m tall.

Northern Andean Shrub Páramo Shrub dominated páramo occurs at altitudes ranging from about 3000-4000 m. However, species composition is extremely variable depending on factors such as geographical position, altitude, humidity, land form and soil type. In the Colombian Cordillera Orientale the characteristic plant families are Asteraceae, Ericaceae and Melastomataceae. The most characteristic shrub genus is the endemic Bacquetia (family?), which includes species such as Bacquetia glutinosa and B. vernicosa. Other characteristic shrubs include the endemic Eupatoria (Ageratina) tinifolium (Asteraceae) and Purpurella grossa (family?), but of particular interest are members of the endemic genus Espeletiopsis (Asteraceae) such as Espeletiopsis corymbosa, E. garciae, E, jimenez-quesadae, E. miska and E. pleiochasia. These species usually occur on steep slopes with moderately acid soils. Other Copyright © 2010 Peter Martin Rhind associated species include the endemic Clethra fimbriata (Clethraceae) and Gaultheria rigida (Ericaceae). On well-drained slopes, the endemic or near endemic shrub Senecio vaccinioides (Asteraceae) may predominate. In the more humid areas the ground layer beneath these Senecio stands are often dominated by bryophytes such as Pleurozium schreberi and Thuidium peruvianum. In other places, particularly in the more humid zones, such as around the headwaters of the Rio Casanare, well developed stands of the endemic Eupatoria tinifolia (Asteraceae) occur. Here the associates include various endemic species such as Baccharis prunifolia (Asteraceae), Escallonia myrtilloides (Escalloniaceae), Hypericum laricifolium (Hypericaceae), Miconia salicifolia (Melastomataceae) and Vallea stipularis (Elaeocarpaceae).

Northern Andean Dwarf Shrub Páramo Ranging in altitude from about 3000-3800 m this vegetation is mostly characterized by the bryophyllous rubiaceous dwarfshrub Arcytophyllum nitidum. If undisturbed it can reach about 1.2 m in height and have a percentage ground cover up to 80%. Locally, however, other woody species, such as the endemic Lobelia tenera (Campanulaceae) and Sporobolus lasiophyllus (Poaceae) can make a significant contribution to ground cover, while less common species include the endemic Castratella piloselloides (Melastomataceae) and Paepalanthus paramensis (Eriocaulaceae). Structurally the vegetation can be divided into two tiers: a dwarf shrub layer, and a herb-graminoid layer mainly dominated by bryophytes. Typical herb layer species include the endemic Oreobolus obtusangulus subsp. rubrovaginatus (Cyperaceae) and Rhynchospora paramorum (Cyperaceae). Among the many other accompanying species are the endemic Geranium multiceps (Geraniaceae), and several other endemic taxa such as Epidendrum chioneum (Orchidaceae), Lourteigia (Eupatorium) microphylla (Asteraceae), Masdevallia coriacea (Orchidaceae) and Spiranthes vaginata (Orchidaceae) reach their maximum extent within the dwarf shrub zone.

Northern Andean Bamboo Páramo Páramo dominated by the endemic bamboo Swallenchloa tesselata (Poaceae) is confined to a relatively narrow belt in the more humid zones. In the Colombian Cordillera Orientale, it ranges in altitude from about 3300-4150 m. The common associates include various endemic taxa such as Calamagrostis effusa (Poaceae), Carex pichinchensis (Cyperaceae), Hypericum lancioides (Hypericaceae), Oritrophium peruvianum (Asteraceae), and several species of the curious endemic genus Espeletia (Asteraceae). In some of the more boggy areas, such as on sloping valley floors Swallenochloa can also be found in association with peat mosses such as Breutelia allionii and Sphagnum magellanicum. Here various herbs occur such as the endemic Eriocaulon microcephalum (Eriocaulaceae), Lachemilla nivalis (Rosaceae), Luzula gigantea (Juncaceae), Niphogeton lingula (Apiaceae), Valeriana plantaginea (Valerianaceae) and a variety of Espeletia species including E. grandiflora, E. incana, E. lopezii, E. murilloi and E. summapacis. The peat in these zones has been dated at up to 5000 years old. On relatively steep slopes species such as the endemic Eryngium humile (Apiaceae) become more conspicuous together with further espeletias such as E. annemariana, E. curialensis, E. cleefii and E. discoidea. In the better-drained areas another suite of species may be encountered. Here the endemic bunchgrass Calamogrostis effusa (Poaceae) may become co dominant with or even dominant over Swallenchloa. The associated flora is again dominated by endemic taxa such as Calamagrostis bogotensis (Poaceae), Castratella piloselloides (Melastomataceae), Paepalanthus andicola (Eriocaulaceae), Sisyrinchium pusillum (Iridaceae) and various espeletias like E. congestiflorus (Asteraceae).

Northern Andean Bunchgrass Páramo Páramo characterized by bunches or tussocks of the endemic grass Calamagrostis effusus (Poaceae) ranges in altitude from about 2900-4500 m on moderately acid soil and where foggy conditions often prevail. It generally includes a scattering of stem rosettes of the endemic genera Espeletia and Espeletiopsis (Asteraceae). In fact, several species such as Espeletia barclayana, E. brachyaxiantha, E. jaramilloi and Espeletiopsis corybosa, E. guacharaca, E. muiska and E. colombiana are more or less restricted to bunchgrass páramo. Other common species may include the endemic Castratella piloselloides, C. rosea (Melastomataceae), Cortaderia sericantha (Poaceae), Gnaphalium antennarioides, Hieracium avilae (Asteraceae) and Lobelia tenera (Lobeliaceae), many of which are sessile rosettes or tufted species. At the highest parts of this zone (3900-4500 m) Calamagrostis effusus can attain ground cover percentages of over 50%. Here the common stem rosette species are Espeletia lopezii, E. cleefii, E. azucarina and Espeletiopsis colombiana, E. guacharaco and E. santanderensis, and they are typically accompanied by the endemic dwarf shrubs like Diplostephium colombianum (Asteraceae) and Loricaria complanata (Asteraceae).

Northern Andean Super Páramo The super páramo is the highest vegetation belt of the tropical northern Andes ranging in altitude from about 3500-4800 m. The zone includes a rich collection of endemic vascular plants. For example, there is a particularly diverse assemblage of endemic species of Senecio (Asteraceae). Many of these, such as the herbaceous Senecio cocuyanus, S. adglacialis, S. supremus, S. pasqui-andinus and the shrubby S. cleefii and S. guicanensis can be found in the Sierra Nevada del Cocuy, but several species are confined to a single summit or range. Senecio santanderensis, for example, is only known from the Páramo de Santurbán and the Páramo de Almorzadero. Other endemic species have their distributions centred on certain areas. Cerastium imbricatum (Caryophyllaceae), Diplostephium rupestris (Asteraceae), Geranium multiparitum (Geraniaceae), Ourisia muscosa (Plantaginaceae), Rumex tolimensis (Polygonaceae) and Werneria humilis (Asteraceae), for example, are centred on Colombian and Ecuadorian super páramos, while endemics such as Distichia muscoides (Juncaceae), Floscaldasia hypsophila (Asteraceae) and Werneria crassa (Asteraceae) have wider distributions.

In the lower super páramo up to about 4500 m, an open dwarf scrub formation dominated by the endemic Loricaria complanata (Asteraceae) can be found on well-drained soils and rocky outcrops. In the Colombian Cordillera Oriental, associated species include the endemic Agrostis haenkeana (Poaceae), Aciachne pulvinata (Poaceae), Carex pygmaea (Cyperaceae), Lachemilla nivalis (Rosaceae), Puya triane (Bromeliaceae) and Senecio cocuyanus (Asteraceae). In other places particularly on terminal moraines in the Sierra Nevada del Cocuy, a low scrub dominated by Senecio vaccinioides and the endemic Diplostephium rhomboides (Asteraceae) may be encountered. Common associates are the endemic Espeletia lopezii (Asteraceae), Luzula racemosa (Juncaceae) and Senecio formosus (Asteraceae). In undisturbed areas, a thick layer of the possibly endemic acrocarpous moss Zygodon pichinchensis covers many of the branches and trunks of this association. Also found locally in the more humid areas of the lower super páramo of the Sierra Nevada del Cocuy, for example, are stands dominated by stem rosettes of the endemic Espeletia cleefii and Espeletiopsis colombia (Asteraceae). Common associates are the endemic Agrostis breviculmis (Poaceae), Castilleja fissifolia (Orobanchaceae) and Gnaphalium antennarioides (Asteraceae). In places there are extensive areas of unstable gravel screes, which are regularly moving due to the action of freeze and thawing. Here the endemic, rosette species Senecio niveo-aureus (Asteraceae) is often the most

Copyright © 2010 Peter Martin Rhind characteristic plant. Associates include the giant Lupinus alopecuroides, but many other ecological zonal can be found in the lower super páramo. For example, a zone dominated by the endemic Draba pamplonensis (Brassicaceae) has been recorded in the Sierra Nevada de Mérida, Venezuela, but so far this has not been found the Colombian páramos. The upper super páramo (about 4500-4800 m) shows a distinct reduction in vascular plants, but a few, such as the endemic Luzula racemosa (Juncaceae) and Senecio niveo- aureus (Asteraceae), have been found in sheltered places in the Colombian Cordillera Oriental. Close to the snowline the only life forms include a few lichens such as Stereocaulon vesuvianum and bryophytes like as Racomitrium crispulum.

Northern Andean Aquatic Quillwort (Isoetes) Vegetation These comprise communities of low nutrient páramos lakes dominated by endemic species of Isoetes (Isoetaceae) and aquatic bryophytes. These range in height from a few centimeters (e.g Isoetes socia) to about 60 cm in the giant Isoetes cleefii. Other species include Isoetes andicola, I. boyacensis, I. glacialis, I. karstenii and I. palmeri. All of these species belong to the section Laeves, which appears to have evolved in the neotropics and most are endemic to the tropical Andes. Isoetes karstenii forms a more or less closed community in some of the highest super páramos lakes (up to altitudes of 4425 m), which are often devoid of all other vascular plants. Typical bryophytes include Blindia magellanica, Isotachis serrulata and Fontinalis bogotensis. The tiny plants of Isoetes socia dominate shallow lakes of the high páramo. Here the few vascular plants include Elatine chilensis and the endemic Crassula bonariensis (Crassulaceae) and Ranunculus mandonianus (Ranunculaceae). Isoetes andicola, on the other hand, is completely different. It forms long boggy hummocks up to 80 cm thick along mineral shores in high altitude lakes. Few other species can be found here but the endemic Oritrophium limophilum (Asteraceae) and Plantago rigida (Plantaginaceae) may be present. Isoetes cleefii is also unusual in forming high (20-60 cm) dense communities in clear lakes of the high grass páramo with few other species, although bryophytes such as Calypogeia andicola may be present. Isoetes palmeri is charactersitic of peaty páramo lakes surrounded by boggy areas. A number of herbaceous amphiphytes, such as Eleocharis acicularis and Hydrocotyle ranunculoides are also charactersitic of these lakes. Isoetes glacialis, as the name suggests, occurs in high glacial lakes. These stands are often so dense that virtually all other species are excluded. Finally Isoetes boyacensis is a common dominant in pools on the calcareous slopes of the Páramo de Almorzadera.

Northern Andean Aquatic Vegetation with Tillaea paludosa Vegetation dominated by the endemic Tillaea paludosa (Crassulaceae) is generally found in the shallow small páramo lakes and pools or along the shores of large, deep páramo lakes. Many of these are mesotrophic as opposed to the more nutrient poor (oligotrophic) condition of the ‘Isoetes’ lakes. Other aquatic herbs include Limosella australis and the endemic Juncus ecuadoriensis (Juncaceae), Lilaeopsis schaffneriana (Apiaceae) and Ranunculus limoselloides (Ranunculaceae). Similar aquatic communities have been found in the afro-alpine zone of several African mountains including Kilimanjaro. Here the dominant species include Crassula granvikii and Limosella africana.

Northern Andean Aquatic Vegetation with Equisetum bogotense Pure stand of Equisetum bogotense up to about 25 cm high occur in various Andean aquatic conditions including lakes and rivers such as the Rio Lagunillas (Sierra Nevada del Cocuy). This species is widely distributed in the tropical Andes and also occur in the Galapagos Islands.

Northern Andean Mires and Swamps North Andean mires and swamps may be dominated by bryophytes such as Marchantia plicata, cyperoids such as the endemic Carex bonplandi, C. pinchinchensis and Cyperus rivularis (Cyperaceae), graminoids such as the endemic Calamagrostis ligulata (Poaceae), and herbaceous forbs such as Gratiola peruviana and the endemic Galium trianae (Rubiaceae), Geranium confertum (Geraniaceae) or Lupinus alopecuroides (Fabaceae), or shrubby species such as the endemic Senecio reissianus (Asteraceae). Mires characterized by Marchantia occur in the upper páramo, the grass páramo and the upper forest belt. In the Colombian Cordillera other species include Epilobium denticulatum, E. meridense and the endemic Cardamine bonariensis (Brassicaceae), Cerastium imbricatum (Caryophyllaceae) and Stachys ellipica (Lamiaceae). Galium trianae and Gratiola peruviana are characteristic of certain cyperaceous reed swamps which normally also include the bryophyte Philonotis andina and endemic vascular plants like Lachemilla mandaniana (Rosaceae). This association is found in the humid páramo in places like glacial valley floors and calcareous depressions. Cyperaceous swamps dominated by Carex pinchinchensis have a hummock-hollow relief. They are mainly in the sub páramo or grass páramo and have their optimal development in marshy glacial valleys. Associated species include the endemic Nertera granadensis (Rubiaceae), Valeriana plantaginea (Valerianaceae) and Senecio canescens (Asteraceae). Cyperus rivularis, on the other hand, is more characteristic of poorly drained peat in the wet sub páramo. Lupinus alopecuroides dominates eutrophic wet flushes with a rich herbaceous layer. Other species typically include Mimulus glabratus and the endemic grass Calamagrostis ligulata (Poaceae). The latter species also forms associations with Geranium confertum in páramo mires and marshy lakeshores. Shrubby association in which Senecio reissianus is the dominant shrub occur on eutrophic marshy or peaty ground usually on gently sloping glacial valley floors or in seepage zones. Other species include the endemic Carex pinchinchensis and Rumex tolimensis (Polygonaceae).

Northern Andean Cushion Bogs Andean bogs dominated by low cushion chamaephytes and geophytes are mainly found at altitudes between 3400-4500 m, but in some locations, such as the Bolivian Andes, these have been recorded up to 5400 m. The key species often include the endemic Castilleja fissifolia (Orobanchaceae), Distichia muscoides (Juncaceae), Plantago rigida (Plantaginaceae) and Werneria pygmaea (Asteraceae). These bogs range across the high tropical Andes from Argentina and Chile to Colombia and Venezuela and correspond roughly to the distribution of the main character species Werneria pygmaea together with some of the small endemic Andean juncaceus genera Distichia, Oxychloe (e.g. Oxychloe andina) and Patosia (e.g. Patosia clandestina). More or less restricted to the northern Andes is the sub-alliance dominated by the endemic Oritrophium limnophilum (Asteraceae) and Werneria pygmaea. This occurs in small, deep valleys and on glacial valley floors, and commonly includes a number of endemic species with very limited distributions including Erigeron paramensis (Asteraceae), Floscaldasia hypsophila (Asteraceae), Vesicarex collumanthus (Cyperaceae) and Werneria crassa (Asteraceae). In places the latter may become dominant in its own right and may be associated with the endemic Lysiopomia sphagnophila (Lobeliaceae), but various other association occur. Another example includes cushion bogs characterized by Altensteinia paludosa and the endemic Castilleja fissifolia (Orobanchaceae) and Gentiana sedifolia (Gentianaceae) together with various bryophytes. This alliance is characteristic of partially filled glacial lakes, and in some of these the cushions actually float. Others are either soligenous or ombrogenous with the latter occurring in the highest parts of bogs and completely

Northern Andean Dwarf Forest of Polylepis The arborescent genus Polylepis (Rosaceae) is endemic the high tropical Andes. Palynalogical studies show that the genus has been established in the Andes for at least 2.7 million years, and certain species are considered to grow at altitudes higher than any other arborescent angiosperm in the World. They can on occasion be found growing at elevations up to 5200 m. There are 15 species altogether including Polylepis lanuginosa, P. reticulata and P. weberbaueri in the Ecuadorian Andes. Polylepis quadrijuga is endemic to the Colombian Cordillera Oriental where it forms dwarf forests. These are especially well developed on the western Magdalena slopes and grow, for example, as isolated patches in montane grasslands or on boulder scree. Commonly associated species include the endemic Galium canescens (Rubiaceae), Miconia andina (Melastomataceae), Niphogeton ternata (Apiaceae) and Senecio formosus (Asteraceae). Other less common endemic includes Peperomia hartwegii (Piperaceae). An interesting austral-antarctic element is represented by the Dysopsis glechomoides (Euphorbiaceae). It also occurs in the temperate forests of Chile and Juan Fernandez.

Northern Andean Dwarf Forest of Hesperomeles Isolated stands of dwarf forest dominated by endemic genus Hesperomeles (Rosaceae) have been recorded in various parts of the high tropical Andes. Wet forest of Hesperomeles lanuginosa can be found, for example, in the timberline zone at 3700-3750 m in the Colombian Cordillera Central and on the Páramo of Barragán.

Northern Andean Dwarf Forest of Escallonia Dwarf forest dominated by the endemic Escallonia myrtilloides (Escalloniaceae) occurs throughout the high tropical Andes. In the Colombian Cordillera Oriental, it ranges from about 2650-3750 m altitude and stands have been recorded along cloud forest timberlines. Common associates include endemic woody taxa such as Acnistus quitoensis (Solanaceae), Chusquea scandens (Poaceae), Espeletia tapirophila (Asteraceae), Euphorbia salicifolium, E. tinifolium (Euphorbiaceae), Miconia cleefii, M. salicifolia (Melastomataceae) and endemic herbaceous species like Calceolaria penlandii (Calceolariaceae) and Rumex tolimensis (Polygonaceae). However, in well-developed forests, such as those in the Ecuadorian Cordillera Occidental, Escallonia myrtilloides can form almost pure stands.

Northern Andean Dwarf Forest of Gaultheria Ericaceous dwarf forest dominated by the endemic Gaulthera ramosissima (Ericaceae) together with the endemic Aragoa perez-arbelaeziana (Plantaginaceae) and various Asteraceae shrubs have been recorded in the Chorreras Valley on the western side of Páramo de Sumapaz at elevations of about 3750 m. The genus Aragoa has its main centre distribution in the Colombian Cordillera Oriental, and Aragoa perez-arbelaeziana is the only tree species in the genus. On the forest floor there is usually a dwarf shrub layer comprising various Vaccinium species and the endemic Disterigma empetrifolium (Ericaceae), while other endemic species such as Oxalis medicaginea (Oxalidaceae) are found in the field layer. At ground level, a thick mat of liverworts often covers the litter, and the trees are usually festooned in a rich epiphytic flora mainly comprising the bryophyte Frullania and the lichen Usnea. This is a clear indication of wet atmospheric conditions which here is mainly caused by fog.

Northern Andean Dwarf Forest of Gynoxys Usually occurring as isolated stands in open páramo or on rocky slopes, dwarf forest dominated by various endemic species of Gynoxys (Rosaceae) can be found throughout the high tropical Andes. Gynoxys albivestita dwarf forests occur in the Sierra Nevada del Cocuy between 3900-4000 m. The trees can reach heights of 8 m and are usually associated with the endemic Acnistus quitoensis (Solanaceae), Solanum bogotensis (Solanaceae) and Valeriana arborea (Valerianaceae). In Páramo de Chisacá, Gynoxys subhirsuta becomes one of the dominant dwarf forest species. These forests occur on boulders at the base of steep wet cliffs at the southern end of Lake Laguna Negra. Associated species include various hygrophytic bryophytes such as Sphagnum magellanicum and a selection of endemic vascular plants like Myrrhidendron glaucescens (Apiaceae). Other Gynoxys species include G. hirsuta, G. paramuna, G. subcinerea and G. trianae and several can form communities in their own right.

Northern Andean Alpine Meadows There are various types of alpine meadow grasslands in the Andes. Among the dominant grass taxa are the small, endemic tussock species Agrostis foliata and Lorenzochloa erectofolia and the endemic cushion-like species Aciachne pulvinata and Muhlenbergia fastigiata (Poaceae). Aciachne and Lorenzochloa represent monotypic tropandean genera. Grasslands dominated by Lorenzochloa tend to be slightly zerophytic and in the Colombian Cordillera Oriental occur at altitudes ranging from 3500-4350 m. Here the associated species include the endemic Espeletia argentea (Asteraceae), Orthrosanthus chimboracensis (Iridaceae), Paspalum bonplandianum (Poaceae) and Satureja nubigena (Lamiaceae). This association is also rich in Cladonia lichen species. Aciachne grassland also has a zerophytic character. It occurs in dry depressions and on gently sloping dry ground, and can be found throughout the high tropical Andes. Apparently, Aciachne retains moisture from fog and its growth often reflects the direction the fog originates from. Depending on location the associated species may include the endemic Agrostis triochodes, Bromus lanatus (Poaceae), Eryngium humile (Apiaceae), Lachemilla orbiculata (Rosaceae), Niphogeton dissectum (Apiaceae), Oreomyrrhis andicola (Apiaceae), Senecio repens (Asteraceae) and Sisyrinchium trinerve (Iridaceae). Muhlenbergia fastigiata is characteristic of wet meadows from the upper forest line at about 3500 m to the lowermost limit of the super páramo at 4250 m. The species is widely distributed in the tropical Andes, but the number and composition of associate species largely depends on altitude. Some typical species include the endemic Carex bonplandii (Cyperaceae), Galium trianae (Rubiaceae) and Werneria pygmaea (Asteraceae). The graminoid layer typically has a bluish tinge. Grasslands characterized by Agrostis foliata are usually pioneer communities of humid sandy or silty beaches in the super páramo lakes up to an altitude of about 4700 m. A peculiar feature of this species of Agrostis is its stiff, purplish blades. Acrocarpous mosses make up most of the associated species but other vascular plants may be present such as the endemic grass Calamagrostis ligulata (Poaceae).

Northern Andean Alpine Cushion Formations Cushion formations dominated by the endemic Azorella multifida (Araliaceae) can be well developed at altitudes ranging from about 4000-4200 m. Good examples can be seen on the high volcano Nevada de S. Isobel in the Colombian Cordillera Central. At the highest altitudes these formations may be simply represented by solitary cushions of Azorella, which can reach heights of up to 40 cm. In less exposed areas other endemic species may be present such as Gentiana sedifolia (Gentianiaceae) and Lysipomia sphagnophila (Campanulaceae) together with various bryophytes such as Tortula andicola and Zygodon pichinchensis. In fact, a moss layer may cover many of the cushions.

Northern Andean Alpine Bamboo Groves Locally at altitudes ranging from 2900-4000 m there are dense stands of the unusual endemic bamboo Neurolepis aristata (Poaceae). It occurs throughout the tropical Andes in the border areas between humid Andean forest and Swallenchloa bamboo páramo, and can reach heights of up to 3 m. In a number of places it achieves almost 100% ground cover with no discernable herbaceous layer. However, there is often a well-shaded ground layer consisting almost entirely of hygrophytic bryophytes.

Northern Andean Montane Forest Andean mountain forests are major centres of biodiversity with large numbers of endemic and restricted range species. In Ecuador alone they harbour more than 16,000 vascular plants – 40% more than the total number for Europe. In terms of species composition they can be broadly divided into lower and upper montane forests. In Ecuador’s Reserva Floristica Rio Guajalito between 1800-2000 m, the lower or sub-montane forests have a clear stratification in terms of plant family composition. Cyatheaceae (tree ferns), Melastomataceae and Rubiaceae dominate the lower stratum with species such as Palicourea ovalis and the endemic Cyathea caracasana var. boliviensis (Cyatheaceae). Important mid-canopy families are Euphorbiaceae, Lauraceae and Rubiaceae with species such as Guarea kunthiana and the endemic Cybianthus peruvianus (Myrsinaceae) and Elaegia utilis (Rubiaceae). The main upper-canopy families are Euphorbiaceae, Meliaceae and Myrtaceae with species such as Bombacopsis squamigera, Cedrela odorata and the endemic Myrcianthus rophaloides (Myrtaceae). Other endemic trees and shrubs of these forests include Billia colombiana (Hippocastanaceae), Cecropia maxima (Cecropiaceae), Nectandia obtusata, Ocotea rugusa (Laureaceae), Meriana acostae, Miconia dapsiliflora (Melastomataceae), Ruagea tomentosa (Meliaceae) and Sepium verum (Euphorbiaceae). Upper montane forest sometimes referred to as ‘Andean Forest’ can be found at elevation ranging from 2000-2900 m. In Ecuador’s Parque Nacional Podocarpus, the dominant tree families in ranked order are Melastomataceae, Cunoniaceae, Ternstroemiaceae, Lauraceae, Celastraceae, Myrsinaceae, Rubiaceae, Aquifoliaceae, Symplocaceae and Araliaceae. Tree species of particular importance are Laplacea speciosa and the endemic Cyathea caracasana (Cyatheaceae) and Weinmannia glabra (Cunoniaceae). Other important endemic trees and shrubs include Critoniopsis sevillana (Asteraceae), Graffenreida harlingii, Meriana furvanthera, Miconia caelata (Melastomataceae), Hedyosmum purpurascens (Chloranthaceae), Orthaea fimbriata (Ericaceae), Persea campii (Lauraceae), Symplocos canescens (Symplocaceae) and Vallea ecuadorensis (Elaeocarpaceae). Average tree height is about 7.5 m but some trees grow to about 16 m. However, there does not appear to be a clear stratification. The ground layer consists of a dense tangle of herbs, slender shrubs, root climbers and bamboos, and the epiphytic flora is particularly rich with numerous mosses, ferns and orchids. There are also a number of parasitic shrubs including the primitive, endemic mistletoe Gaiadendron punctatum (Loranthaceae).

Further information required.

References

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