Included here is the Chaco or Gran Chaco and Southern Andean Yungas. Chacoan vegetation covers the vast plains of north-central Argentina, western Paraguay, southeast Bolivia and extends into Brazil along the a narrow strip parallel to the River Paraquay in Mato Grosso do Sul. This area represents a massive outwash plain built up from accumulations of Quaternary sediments derived from the eastern Andes.

Sierra Chaco Woodland

In the Argentinean uplands two woodland zones are recognized. On dry, sunny slopes up to about 1800 m the woodlands are mainly dominated by the endemic Schinopsis haenkeana (Anacardiaceae), while on the cooler slopes Lithrea ternifolia and Fagara coco are the main species. Other species generally associated with these woodlands include Bougainvillea stipitata, Kageneckia lanceolata, Prosopis chilensis, P. torquata, Ruprechtia apetala and the endemic or near endemic Aspidosperma quebracho-blanco (Apocynaceae), Geoffroea decorticans (Fabaceae) and Prosopis nigra (Fabaceae). In the Paraguayan uplands (Cerros León and Cabrera) other woodland types occur. On well-watered slopes, for example, there are deciduous woodlands dominated by Anadenanthera colubrina, while other species include Amburana cearensis, Aspidosperma pyriformis and Pterogyne nitens.

Calycophylla multiflora (palo blanco) Transitional Forest

Forest dominated by the magnificent Calycophylla multiflora, are situated in the sub Andean piedmont regions of southwest Bolivia and northwest Argentina, which is zone of transition between the Chaco and Yungas ecozones. The rainfall in this zone is intermediate between these two regions and has more of a monsoon character. The forest canopy can reach heights of 30 m and interestingly these forests have a higher number of deciduous species (79%) than any other subtropical seasonal forest. Certain trees, such as Calycophylla multiflora and Phyllostylon rhamnoides, have straight, white boles up to one meter in diameter. Other trees include Amburana cearensis, Anadenanthera colubrina, Astronium urundeuva, Corda trichotoma, Enterolobium contortisiliquum, Myroxylon balsamum, Patagonula americana, Ruprechtia laxiflora and Senna spectabilis. There is usually a dense shrub layer up to 2 m high making movement through the forest difficult, and there are abundant epiphytes, vines and lianas. Forests of Calycophylla multiflora together with Acosmum cardenasii can also be found in northern Paraguay. They also typically occur in transition zones usually in seasonally flooded areas such as riverbeds with seasonal drainage. Other trees include Casearia gossypiosperma and Phyllostylon rhamnoides, while common under storey species are Celtis iguanea, Fagara pterota, Helietta mollis and Lasiacis sorghoides.


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