Bryophytes of the Chaco Serrano
The Chaco Serrano, or Montane Chaco, is located in south central Bolivia, bordered on the west by the sub-Andean Tucuman-Bolivian montane and Dry Inter-Andean valleys, and in the east by the Chaco. Chaco Serrano vegetation extends into northwest Argentina. Less than 1% (23,176 km2) of the land surface of Bolivia is comprised of Chaco Serrano forest. This vegetation type is found in the Bolivian departments of Santa Cruz, Chuquisaca and Tarija. Elevation ranges from ca. 700 to 2000 meters. The annual average temperatures range from 18-22º C; the area is influenced by the southerly winds (surazos). Annual average precipitation ranges from 700-1000, with approximately 6-7 dry months.
Map of the Chaco Serrano. Courtesy of FAN (Fundación Amigos de la Naturaleza), Santa Cruz de la Sierra, Bolivia.
The vegetation, one of the driest in the highland forested ecoregion in Bolivia, is characterized by open or closed dry deciduous forested. The region is characterized topographically by low mountains and valleys, essentially the foothills of the Cordillera Oriental. The knee of the Cordillera Oriental is essentially the border separating the humid Yungas to the northwest and the dry Chaco Serrano to the south. Vascular plant diversity is presently unknown. Tree diversity is estimated ca. 200 species. Important vascular plant families include: Anacardiaceae, Apocynaceae, and Leguminosae. Important tree species include: Anadenanthera colubrina, Astronium urundeuva, Lithraea ternifolia, Schinopsis haenkeana, Tabebuia impetiginosa, and Zanthoxylum coco; areas with higher humidity include Calycophyllum multiflorum and Schinopsis cornuta. Vascular epiphyte diversity is estimated at more than 40 species represented mainly by the Bromeliaceae. Endemism is unknown. The floristic affinities of the Chaco Serrano are thought to be with the Chiquitano ecoregion (and some treat the former as a subset of the latter).
The Chaco Serrano is the least diverse ecoregion in the Bolivian highlands for bryophytes. Little exploration and inventory has been conducted in this ecoregion. Eighteen mosses (9 families, 14 genera) and no hepatics are recorded for the Chaco Serrano ecoregion. There maybe 40 or possibly 50 mosses and likely 10-20 hepatics. At present, and likely in the future, the Pottiaceae is the most diverse family. Other characteristic families typical of dry or semi-dry regions found in the montane or lowlands elsewhere in Bolivia include the Leptodontaceae (Forsstroemia) and Stereophyllaceae. Hepatics that can be anticipated in this ecoregion include several thalloid genera (Marchantia, Plagiochasma, possibly Riccia) and at least a few species of Frullania. The likely floristic relationship with other ecoregions includes the adjoining lowland Chaco and highland dry inter-Andean valleys. Future inventory efforts in the Chaco Serrano as well as the Chaco should help to elucidate the bryophyte ecoregion affinities.
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.
Moss Checklist of the Chaco Serrano
Erpodium beccarii Müll. Hal. ex Vent.
Ptychomitrium lindmanii (Broth.) Paris
Helicophyllum torquatum (Hook.) Brid.
Forsstroemia coronata (Mont.) Paris
Forsstroemia producta (Hornsch.) Paris
Forsstroemia trichomitria (Hedw.) Lindb.
Lindbergia mexicana (Besch.) Cardot
Pterogoniadelphus assimilis (Müll. Hal.) Ochyra & Zijlstra
Macrocoma tenuis (Hook. & Grev.) Vitt subsp. sullivantii (Müll. Hal.) Vitt
Gertrudiella validinervis (Herzog) Broth. var. validinervis
Plaubelia sprengelii (Schwägr.) R.H. Zander
Pseudocrossidium linearifolium (Müll. Hal.) J.A. Jiménez & M.J. Cano
Syntrichia chisosa (Magill, Delgad. & L.R. Stark) R.H. Zander
Syntrichia fragilis (Taylor) Ochyra
Syntrichia xerophila (Herzog) S.P. Churchill [=Pseudocrossidium]
Entodontopsis leucostega (Brid.) W.R. Buck & Ireland
Eulacophyllum cultelliforme (Sull.) W.R. Buck & Ireland
Stereophyllum radiculosum (Hook.) Mitt.