Azonal vegetation

--- cushion bogs, Sphagnum bogs, grass-moss mires, flush vegetation and lakes, ponds and streams ---

Text by prof dr. A.M. Cleef, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam.

Glacial valley floors are usually peaty and wet as result of the presence of quite a number of small terminal moraines. Flush communities, mires and cushion bogs are prominent here; Distichia muscoides cushion bog from about 4200 m upslope with Plantago rigida cushions in the lower part (3800-4200 m). Also cushions of Oreobolus cleefii seem to form part of the cyclic events in the Distichia bog. 


West side of the Sierra Nevada del Cocuy

There are numerous glacial lakes in this altitudinal zone, with a lake floor growth of e.g. Isoëtes karsteniiSphagnum peat bog is scarce probably also because of trampling, manuring and grazing by cattle and the relatively dry climate.

A larger Sphagnum peatbog with giant Puya aristiguietae is present at the base of the Cóncavo páramo. The final succession on Sphagnum peat is a Diplostephium revolutum dwarf forest. This has been observed at 3950 m in the glacial valley about 1 km SSW of Laguna Grande de los Verdes. Here a 3-5 m well-developed Diplostephium revolutum dwarf forest is  present on top of a former Sphagnum bog. On the border with a terminal moraine with bunchgrasses and Espeletia lopezii stem rosettes appear cushions of Oreobolus cleefii with ground rosettes of Oritrophium peruvianum, dwarfshrub of Pentacalia flosfragans and Sphagnum sancto-josephense.

A species of Elatine and Crassula venezuelensis abound along the amphibic flat parts of the shores of glacial lakes. in the grasspáramo Initial grass mires made up of tussocks of Calamagrostis ligulata have been documented between Valle de Lagunillas at about 3950 m and 4400 m in the upper Cóncavo páramo. At about 4000 m they combine with large phorbs as Senecio guascensis and Lupinus aff. alopecuroides and pleurocarpous mosses, such as Calliergonella cuspidatum, Scorpidium scorpidioides and species of Drepanocladus.

Also a shallow lake floor, dammed by a terminal moraine in the Lagunillas valley, massive growth of Eleocharis macrostachya combined with  floating Utricularia has been documented. Floating leaflets of Ranunculus nubigenus are frequent along the shores of glacial lakes and in ponds.

Flush communities with Werneria pygmies building wet meadows on glacial valley-floors are commonly sighted. Sometimes they combine with large groundroesettes of Lupinus cf. alopecuroides. Pioneering tussocks of Cortaderia hapalotriche, Loricaria complanata dwarfed shrubs with ringlike Mniodes kunthiana and Oreobolus cleefii cushions are found on unsafe grayish and muddy surfaces with a sheet of superficially running water in the transition to the superpáramo.

Massive Espeletia lopezii growth is present where later a large Distichia muscoides peat bog develops; the first cushion species are already present at 4350 m in the Concavo páramo.

In the water-loaded depressions between the moraines in the lowermost superpáramo Espeletia lopezii stem rosettes build a wet high Andean mire type consisting of a matrix of pleurocarpous mosses and rhizomatous vascular species as the tiny Floscaldasia hypsophila with Werneria pygmaea, Carex collumanthus, Carex sp., Lachemilla mandoniana and Castilleja paramicola. Water percolates slowly through this mire system.


East side of the Sierra Nevada del Cocuy

Patches of azonal dwarf forest either of Diplostephium revolutum or Escallonia myrtilloides are established in bamboo-Sphagnum bogs between moraines, Sphagnum growth is most common in this landscape on level position but also creeping upslope the moraines.

Espeletia lopezii stands on the valley bottom are growing together with Oritrophium peruvianum and Sphagnum cf. cyclophyllum (in the lowest parts). At 3500 m the uppermost larger bamboo-Sphagnum bogs may occur with up to 1 m in height bryophyte hummocks around the Chusquea stems.

The azonal vegetation in the upper páramo comprises mainly the cushion bogs on the valley floors. These appear from about 3700-4000 m with Plantago rigida cushion bog in the lower part and at higher elevation (gradually) they are replaced by Distichia muscoides (Juncaceae) cushions. 

Flat areas, with active coarse-sandy sedimentation from the superpáramo contain low shrub of Loricaria complanata and Pentacalia flosfragans with rosettes of Oritrophium peruvianum growing dispersed over the level valley bottom.

From 4150-4200 m upwards Distichia muscoides cushion bogs appear on the humid and wet valley bottom. These bogs are the highest in the tropical Andes (and perhaps world wide) and in the Cocuy they continue at least up to 4400 (4500) m . The largest sized cushion bog is that of Valle de Cojines at about 4100 m. The cushions of Distichia are most firm when young and easily resist human steps. However, cushion epiphytes appear with age, first in the oldest central part, which finally may collapse, building in this way ringlike cushions. With the gradual decay of the Distichia cushions quite a number of species of bryophytes and vascular plants appear. Common bryophyte and lichen species include Campylopus cuspidatus,  Brachythecium sp., Calliergonella cuspidata, Scorpidium sp., Marchantia plicata, Riccardia spp., with Peltigera spand Cladonia meridensis at drier parts of the Distichia cushions.  Herbs include Agrostis breviculmis, Bartsia stricta, Carex collumantus, Floscaldasia hypsophila, Nertera granadensis, Phlegmariurus (Huperzia) cruentus, Phylloscirpus bolivianum, Senecio adglacialis, S. cf. formosus and the rale dwarf shrub Hypericum lancioides. Cushions of Oreobolus cleefii and Xenophyllum crassum are also early present on the decayed Distichia muscoides. Open shrub patches of Pentacalia flosfragrans with its vertical rising stems and dark green small leaves seem to represent a final stage in this successional process. A study with quite a number of small permanent quadrats is needed to get more details of this interesting succession.

Isolated small cushions of Brayopsis colombiana, as early pioneers preceding  the Distichia cushions are found just above the uppermost Distichia cushions.

The glacial lakes are filled with sediments from higher elevation. Along unsafe shores around 4300 m may appear Calamagrostis ligulata with Lachemilla mandoniana, Ophioglossum crotalophoroides, Werneria pygmaea with abundant Riccardia sp. (Laguna Pañuela for example). Most common however are the submerged Isoëtes karstenii in larger waterbodies, and I. palmeri  mostly in smaller lakes. 

Many tiny plants of Isoëtes inconspicua occur as ephemerals in shallow ponds and pools in the lower superpáramo, which may evaporate during the dry season. 

Shallow lakelets in the upper grasspáramo may evaporate also in the dry season. Ephemerals of Limosella australis are dominant and flowering, with patches of Ranunculus nubigenus.

Crassula venezuelensis is rare in the lower superpáramo (only one submerged record at 4370 m), but common in ponds and lake shores in the upper grasspáramo.

Streams running down in the superpáramo and upper grasspáramo contain Isotachis serrulata growth, sometimes forming masses of floating liverwort-peat as observed at ca 4350 m between Valle de Cojines and Laguna Rincón.