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Las Briofitas. Bolivia Ecologica 59
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Bryophytes of the Dry Inter-Andean Valleys

 

Dry Inter-Andean Valley vegetation near Pampagrande. Photograph by S. Churchill.

The dry inter-Andean valleys occur in small to sometimes extensive isolated areas from Colombia to northwest Argentina. In Bolivia this zone is primarily found in the interior of the Eastern Cordillera (Wood 2006). Approximately 4% of the land surface of Bolivia is comprised of dry inter-Andean valleys. Elevation ranges from ca. 500 to 3300 meters, but in general from 1000-2500 meters.

Map of the Dry Inter-Andean Valleys. Courtesy of FAN (Fundación Amigos de la Naturaleza), Santa Cruz, Bolivia.

 

 The most extensive areas are located south of latitude 18ºS found in the departments of Cochabamba, Santa Cruz, and Chuquisaca; smaller, isolated areas occur in the departments of La Paz and Tarija. Mean temperatures range from 12-16º (min. <0º, max, >30º) and annual mean precipitation ranges from 500-700 mm or less, with ca. 6-8 dry months.

 

The vegetation of this region is found in valleys, hills, and often on the lower slopes of the serranías. It might be said that almost every plant, from herb to tree, has either spines or thorns. Plant communities or formations vary dramatically, from bare, exposed slopes with widely spaced trees, few herbs and shrubs to densely wooded, almost impenetrable thickets or forest, with or without an understory of spiny bromeliads and cactus, and in some localities dominated by the presences of tall columnar cactus. Little of the natural vegetation of the dry inter-Andean valleys remains. Several hundred years of human occupation has altered much of the landscape, through wood gathering, grazing (cattle, sheep, and particularly goats).

 

Neoraimondia herzogiana near Pampagrande. Photograph by S. Churchill.

 

Vascular plant diversity of the dry inter-Andean valleys is estimated at ca. 1300 species distributed among 519 genera and 111 families (López 2000). About 16% (209 spp.) are considered endemic to the Bolivian dry valleys. The ten most diverse families include: Asteraceae (209 species, 76 genera), Cactaceae (121 species, 25 genera), Poaceae (116 species, 55 genera), Fabaceae s.l. (107 species, 46 genera), Solanaceae (59 species, 16 genera), Bromeliaceae (56 species, 5 genera), Malvaceae (36 species, 14 genera), Euphorbiaceae (36 species, 9 genera), Verbenaceae (29 species, 9 genera), and Lamaceae (25 species, 6 genera). Tree diversity is estimated at 200 or less species. Notable trees include Acacia caven (Molina) Molina (Fabaceae s.l.), Astronium urundeuva (Allemão) Engl. (Anacardiaceae), Cardenasiodendron brachypterum (Loes.) F.A. Barkley (Anacardiaceae), Erythrina falcata Benth. (Fabaceae s.l.), Kageneckia lanceolata Ruiz & Pav. (Rosaceae), Prosopis alba Griseb. (Fabaceae s.l.), Schinus molle L. (Anacardiaceae), Schinopsis haenkeana Engl. (Anacardiaceae), and Tipuana tipu (Benth.) Kuntze (Fabaceae s.l.). Numerous species of Cactaceae are present (74 endemic), including the tall columnar cactus Neoraimondia herzogiana (Backeb.) Buxb.

 

 

Bryophyte Diversity

 

At present 62 mosses (60 species and 2 varieties) distributed among 34 genera, and 17 families are recorded from the dry inter-Andean valleys. The estimated bryophyte diversity is ca. 90-100 species.  The single most diverse family is the Pottiaceae, comprising nearly half of the species presently recorded. Most families comprise genera and species found in various ecoregions, e.g., Bryaceae. The only families that are typical of xerophytic vegetation include the Erpodiaceae and Stereophyllaceae. Most genera are only represented by three or less species. The genus Syntrichia is most diverse, with 11 species. At least with regard to the Pottiaceae, Syntrichia of the dry inter-Andean valleys is the counterpart of the equally diverse genus Leptodontium of open and forested humid montane.

 

The floristic affinities of mosses found in the dry inter-Andean valleys is clearly related to the xerophytic ecoregions of Chaco Serrano (essentially the outer sub-Andean flank of the eastern cordillera) and further to the east, the extensive Chaco lowlands. Neither the Chaco Serrano nor Chaco ecoregions have been sufficiently sampled to provide a viable comparison. Puna and Prepuna are also floristically related to the dry inter-Andean valleys, particularly at high elevations.

Gertrudiella validinervis (Churchill 20925). Photograph by J.D. Parra.

 

Little is known about hepatic diversity of the dry inter-Andean valleys, certainly less than mosses. Only Frullania ericoides and Porella reflexa are presently recorded as epiphytes, and for terrestrial thalloid hepatics only Plagiochasma rupestre can be listed. Thalloid heptaics are likely to be well represented in this ecoregion.

 

The ecological role played by bryophytes in the dry inter-Andean valleys is minor. In general bryophytes of this region are rarely abundant (in terms of biomass) or very common (in terms of frequency). Occasionally one finds rather extensive patches of terrestrial mosses often associated with developed soils, e.g., Bryum spininervium, Gertrudiella validinervis, Pleurochaete luteola, and Pseudocrossidium replicatum. Certainly bryophytes play a role in arresting erosion, particularly along streams or exposed, eroding slopes and banks.

 

Epiphytes

 

Epiphytes are almost exclusively found on trees, not shrubs. On trees epiphytes are found most frequently either at the base and inclined trunks or large branches. The bark texture is usually coarse and somewhat thick. Twig epiphytes are absent, except possibly at higher elevations. Occasionally some populations can be somewhat abundant, e.g., Braunia and Macrocoma.

 

Hepatics: Frullania ericoides, Porella reflexa. Mosses: Braunia plicata, Cryphaea brevipila, Entodontopsis leucostega, Erpodium acrifolium (rare), Erpodium beccarii., Erythrodontium longisetum, Fabronia ciliaris var. ciliaris, Fabronia ciliaris var. polycarpa, Lindbergia mexican, Macrocoma orthotrichoides, Macrocoma tenuis ssp. sullivantii, Orthotrichum diaphanum var. podocarpi, Orthotrichum pungens, Syntrichia amphidiacea, Syntrichia chisosa, Syntrichia fragilis, Syntrichia papillosa, Syntrichia serripungens, Tortella humilis.

 

Rio Pilcomayo south of Sucre, border of Chuquisaca and Potosí. Photograph by S. Churchill.

 

Logs

 Logs, including standing dead trees, are a minor substrate for bryophytes. Typically wood in the form of trunks and branches decompose very slowly, due in part to the pronounced aridity of the region and hardness of the wood.

 

Mosses: Brachymenium systylium, Entodontopsis leucostega, Fabronia ciliaris, Juratzkaea argentinica, Lindbergia mexicana, Macrocoma tenuis ssp. sullivantii, Syntrichia amphidiacea, Syntrichia chisosa, Syntrichia fragilis, Syntrichia papillosa.

 

Soil and Rocks

 

Soil, soil covered rocks, and rocks provide the greatest substrate for mosses (and what few heptatics there are). A few species can be rather abundant with developed soils or sandy soils, e.g., Bryum spininervium, Gertrudiella validinervis, Pleurochaete luteola, Syntrichia obtusissima. Seemingly Pseudocrossidium replicatum is the single most common species encountered, and typically one of most common species to colonize exposed soils in degraded areas. Aquatic, semi-aquatic, streamside mosses found in canyon streams or rivers, often forested, include: Leptobryum wilsonii, Platyhypnidium aquaticum, and Vittia pachyloma.

 

Hepatic: Plagiochasma rupestre. Mosses: Anomobryum julaceum, Brachymenium exile, Bryoerythrophyllum bolivianum, Bryum argenteum, Bryum chryseum, Bryum spininervium, Didymodon australasiae, Didymodon rigidulus var. subulatus, Gertrudiella validinervis var validinervis Gertrudiella validinervis var. serratopungens, Hedwigidium integrifolium, Hyophila involuta, Lorentziella imbricata, Platyhypnidium aquaticum, Pleurochaete luteola, Pogonatum perichaetiale subsp. oligodus, Pseudocrossidium crinitum, Pseudocrossidium replicatum, Syntrichia obtusissima, Syntrichia princeps, Syntrichia ruralis, Syntrichia xerophila, Timmiella barbuloides, Tortella humilis, Trichostomum brachydontium, Trichostomum tenuirostre, Weissia controversa.

 

Selected Literature

 

Antezana, C. & G. Navarro. 2002. Contribución al anlisis biogeogrfico y catlogo preliminar de la flora de los valles secos interandinos del centro de Bolivia. Revista Boliviana de Ecología y Conservación Ambiental 12: 3-38.

López, R.P. 2002. Diversidad floristica y endemismo de los valles secos bolivianos. Ecología en Bolivia 38: 27-60.

López, R.P. & C. Zambrana-Torrelio. 2005. Representation of Andean dry ecoregions in the protected areas of Bolivia: The situation in relation to the new phytogeographical findings. Biodiversity and Conservation 15: 2163-2175.

Wood, J.R.I. 2005. La Guía “Darwin” de las Flores de Los Valles Bolivianos. Darwin Initiative.

Wood, J.R.I. 2006. Inter-Andean dry valleys of Bolivia – floristic affinities and patterns of endemism: Insights from Acanthaceae, Asclepidaceae and Labiatae. Pages 235-256. In: R.T. Pennington, G.P. Lewis and J.A. Ratter (eds.). Neotropical Savannas and Seasonally Dry Forest. CRC Press, Boca Raton, FL.

 

 

Checklist of the Dry Inter-Andean Valleys

 

HEPATICS

 Aytoniaceae

Plagiochasma rupestre (G. Forst.) Steph.

Frullaniaceae

Frullania ericoides (Nees ex Mart.) Mont.

Porellaceae

Porella reflexa (Lehm. & Lindenb.) Trevis.

 MOSSES

 Amblystegiaceae

Vittia pachyloma (Mont.) Ochyra

Brachytheciaceae

Platyhypnidium aquaticum (A. Jaeger) M. Fleisch.

Bryaceae

Anomobryum julaceum (Schrad.) Schimp.

Brachymenium exile (Dozy & Molk.) Bosch. & Sande Lac.

Brachymenium systylium (Müll. Hal.) A. Jaeger

Bryum argenteum Hedw.

Bryum chryseum Mitt.

Bryum spininervium Broth.

Leptobryum wilsonii (Mitt.) Broth. (rare)

Cryphaeaceae

Cryphaea brevipila Mitt.

Entodontaceae

Erythrodontium longisetum (Hook.) Paris

Encalyptaceae

Encalypta asperifolia Mitt. (rare)

Erpodiaceae

Erpodium acrifolium Pursell (rare)

Erpodium beccarii Müll. Hal.

Fabroniaceae

Fabronia ciliaris (Brid.) Brid. var. ciliaris

Fabronia ciliaris var. polycarpa (Hook.) W. R. Buck

Fabronia jamesonii Tayl.

Fissidentaceae

Fissidens asplenioides Hedw. (rare, marginal)

Gigaspermaceae

Lorentziella imbricata (Mitt.) Broth.

Hedwigiaceae

Braunia cirrhifolia (Mitt.) A. Jaeger

Braunia plicata (Mitt.) A. Jaeger

Hedwigidium integrifolium (P. Beauv.) Dixon

Leskeaceae

Lindbergia mexicana (Besch.) Cardot

Macromitriaceae

Macrocoma orthotrichoides (Raddi) Wijk & Margad.

Macrocoma tenuis ssp. sullivantii (Müll. Hal.) Vitt

Orthotrichaceae

Orthotrichum diaphanum var. podocarpi (Müll. Hal.) Lewinsky

Orthotrichum pungens Mitt.

Polytrichaceae

Pogonatum perichaetiale subsp. oligodus (Kunze ex Müll. Hal.) Hyvönen

Polytrichum juniperinum Hedw. (rare)

Pottiaceae

Aloina rigida (Hedw.) Limpr.

Bryoerythrophyllum bolivianum (Müll. Hal.) R.H. Zander

Didymodon australasiae (Hook. & Grev.) R.H. Zander

Didymodon lindigii (Hampe) R.H. Zander

Didymodon rigidulus var. subulatus (Thér. & E.B. Bartram ex E.B. Bartram) R.H. Zander

Erythrophyllopsis fuscula (Müll. Hal.) Hilp.

Gertrudiella validinervis (Herzog) Broth. var. validinervis

Gertrudiella validinervis var. serratopungens (Herzog) R.H. Zander

Hyophila involuta (Hook.) A. Jaeger

Leptodontium capituligerum Müll. Hal. (rare)

Pleurochaete luteola Besch.

Pseudocrossidium austrorevolutum (Besch.) R.H. Zander

Pseudocrossidium crinitum (Schultz) R. H. Zander

Pseudocrossidium replicatum (Taylor) R. H. Zander

Syntrichia amphidiacea (Müll. Hal.) R. H. Zander

Syntrichia chisosa (Magill, Delgadillo M. & Stark) R. H. Zander

Syntrichia fragilis (Taylor) Ochyra

Syntrichia lacerifolia (R.S. Williams) R.H. Zander

Syntrichia obtusissima (Müll. Hal.) R.H. Zander

Syntrichia pagorum (Milde) J.J. Amann

Syntrichia papillosa (Wilson) Jur.

Syntrichia princeps (De Not.) Mitt.

Syntrichia ruralis (Hedw.) F. Weber & D. Mohr

Syntrichia serripungens (Lorentz & Müll. Hal.) R.H. Zander

Syntrichia xerophila (Herzog) S.P. Churchill

Timmiella barbuloides (Brid.) Mönk.

Tortella humilis (Hedw.) Jenn.

Trichostomum brachydontium Bruch

Trichostomum tenuirostre (Hook. & Taylor) Lindb.

Weissia controversa Hedw.

Stereophyllaceae

Entodontopsis leucostega (Brid.) W. R. Buck & Ireland

Juratzkaea argentinica (Thér.) W.R. Buck

Stereophyllum radiculosum (Hook.) Mitt.

 

 
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