Chacoan Humid-Subhumid (or Eastern) Chaco Woodland

Situated in waterlogged areas where soils are often slightly saline these forests are typically dominated by endemic Schinopsis balansae (Anacardiaceae), while other common canopy trees include the endemic or near endemic Aspidospermum quebracho-blanco (Apocynaceae)and Caesalpinia paraquariensis (Fabaceae). A second story usually includes Acacia praecox, Sideroxylon obtusifolium and the endemic or near endemic Geoffroea decorticans (Fabaceae) and Prosopis nigra (Fabaceae).Common under storey species include the endemic or near endemic Achatocarpus praecox (Achatocarpaceae), Castella coccinea (family?), Shinus fasciculatus (Anacardiaceae)and the cactus Opuntia retrorsa. Surprisingly, cacti are an important feature of these woodlands. At field level common herbaceous species are Aechmea distachantha, Dyckia ferox and various grasses. Lianas and vines are very rare but epiphytes are quite common, and epiphytic Tillandsia species are well represented. On the high ground of this eastern zone, there are woodlands transitional to the wetter forests of southern Brazil. Here notable species are Tecoma ipe (Tabebuia impetiginosa), Gleditsia amorphoides, Patagonula americana and several members of the Mytaceae (such as Eugenia uniflora and Myrcianthes cisplatensis). Others include Astronium balansae, Ceiba speciosa, Diplokeleba floribunda and Pithecellobium scalare, and in contrast to the previous woodlands lianas and epiphytes are abundant.


Chacoan Semi-Arid to Arid (or Western) Chaco Woodland

The most extensive vegetation here are medium-stature forests (16-18 m) dominated by the endemic or near endemic Aspidospermum quebracho-blanco (Apocynaceae) and Schinopsis quebracho (Anacardiaceae). A second story up to 12 m high typically consists of Ceiba chodatii, Cercidium praecox, P. kuntzei, and the endemic or near endemic Caesalpinia paraquariensis (Fabaceae), Geoffroea decorticans (Fabaceae), Prosopis alba, P. nigra (Fabaceae), Ziziphus mistol (Rhamnaceae)and a variety of arboreal cacti. The later are a particular feature of these woodlands and include endemic or near endemic species like Cereus validus, Opuntia quimilo, Quiabentia pflanzii and Stetsonia coryne (Cactaceae). The shrub layer may include Cercidium australis, Jodina rhombifolia, Maytenus spinosa, Ximeria americana and the endemic or near endemic Castella coccinea (family?)and Ruprechtia triflora (Polygonaceae).Typical herbaceous species are Bromelia hieronymi, B. serra and Deinacanthon urbanianum. On limey-clayish soils often with impeded drainage other trees such as the endemic or near endemic Aspidosperma triternatum (Apocynaceae), Bulnesia sarmientoi (Zygophyllaceae)and Tabebuia nodosa (Bignoniaceae)may become dominant, while along riverbanks, Calycophyllum multiflorum, Enterolobium contortisiliquum and the endemic or near endemic Acacia caven (Fabaceae) usually become the main species. In places, however, especially on sandy soils, these woodlands become more savanna-like with widely spaced trees of Jacaranda mimosifolia and the endemic Schinus heterophylla and S. quabrancho-colorada (Anacardiaceae), and where saline condition prevail the endemic giant cactus Stetsonia coryne (Cactaceae) becomes more conspicuous. Other endemic or near endemic species include Jatropha matacensis (Euphorbiaceae), Lophocarpinia aculeatifolia (Fabaceae), Mimoziganthus carinatus (Fabaceae), Setiechinopsis mirabilis (Cactaceae), Stenodrepanum bergi (Fabaceae) and many others.


Chacoan 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.


Chacoan Thorn Chaco Woodland

Dense thorn woodland reaching not much more than 3 m in height occurs throughout the Chaco in low lying poorly drained areas. In many of these, especially where the water table is high, the arboreal stratum is reduced to species Prosopis. In eastern areas the endemic or near endemic Prosopis alba and P. nigra (Fabaceae) are often the main species. These stands are common, for example, around swamps and adjacent to streams. In less flooded areas other arboreal species such as the endemic or near endemic Acacia cavens (Fabaceae), Aspidosperma quebracho-blancho (Apocynaceae) and Geoffroea decorticans (Fabaceae) occur, but there is rarely any well developed shrub layer, and ground layer herbaceous species are limited. In the northern Paraguayan Chaco some of the more typical species include Cordia bordasii, Prosopis elata and the endemic or near endemic Bulnesia sarmientoi (Zygophyllaceae), Capparis retusa (Capparaceae), Prosopis rojasiana (Fabaceae), Ruprechtia triflora (Polygonaceae) and Tabebuia nodosa (Bignoniaceae). Other endemic or near endemic species characteristic of these miniature woodlands include Acacia praecox (Fabaceae), Bougainvillea praecox (Nyctaginaceae), Capparis speciosa, C. salicifolia (Capparaceae), Castella coccinea (family?), Jacaratia corumbensis (Caricaceae), Jatropha grossidenta (Euphorbiaceae), Prosopis ruscifolia and P. sericantha (Fabaceae).


Chacoan 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.


Chacoan Cactus Scrub

Cactus scrub dominated by the monotypic genus Stetsonia (Cactaceae) endemic to the Chaco is common in the western Chaco, but moving east it becomes increasingly rare. Stetsonia coryne is a large candelabra-like species that can become particularly dominant in strongly saline soils where much of the ground is either bare or covered in mosses and the clubmoss Selaginella sellowii.


Chacoan Palm Groves

Stands of the endemic, fan-leaved palm tree Copernicia alba (Arecaceae) are features of marshes in seasonally flooded, alkaline soils. It can reach heights of 8-10 m but stands are usually open with variable levels of density. Other arboreal species may include various endemic or near endemic species such as Acacia caven (Fabaceae), Geoffroea decorticans (Fabaceae), Sapium haematospermum (Euphorbiaceae) and Tabebuia nodosa (Bignoniaceae). The field layer is typically dominated by the endemic or near endemic grass Spartina argentinensis (Poaceae) although species of Paspalum may replace it in places. In seasonally flooded parts of northeastern Paraguay and southeastern Bolivia, Copernicia alba is often co dominant with the shrub or small tree Triplaris gardneriana (Polygonaceae) which is endemic to the upper basin of the Paraguay River. Other characteristic species include Albizia inundata and Parkinsonia aculeata


Chacoan Saxicolous Shrubland of Cerron León

Shrublands dominated by Anadenanthera colubrina and Caesalpinia marginata (Fabaceae) are restricted to the isolated mountains system (Serrania de Cerro León) in the northern Paraquayan Chaco. The latter species is largely endemic to the transition zone between Chaco and Cerrado. The vegetation is confined to stony slopes and hill tops and has a dense low canopy about 3-5 m high. Other characteristic shrubs include Astronium urundeuva, Phyllostylon rhamnoides and the local endemic Mimosa bimucronata var. adenocarpa (Fabaceae). Common under storey species include Gymnocalycium paediophilum and G. stenopleurum.


Chacoan Chaco-Cerrado Chaparral

Low sclerophyllous and xeromorphic shrublands dominated by Terminalia argentea and the regional endemic Sphingiphila tetramera (Bignoniaceae) occur in the transition zone to Cerrado in northern Paraguay and southeast Bolivia. These grow on sandy or stony calcareous soils and usually have an open canopy reaching 4-6 m high, but there are occasional emergents of the characteristic, endemic Chaco tree Schinopsis cornuta (Anacardiaceae). In the sub canopy Tabebuia selachidentata and the regional endemic Caesalpinia marginata (Fabaceae) are abundant. However, the diverse flora of this formation is largely made up of Cerrado elements and on siliceous sandstone, Sphingiphila tetramera is replaced by Pseudobombax tomentosa.


Chacoan Spartina Grassland

Grassland dominated by Spartina argentinensis is the most widespread grassland of the low halomorphic soils in the so-called submeridional lowlands of the Santafesinian Chaco, Argentina. The area is normally flooded at the end of summer but becomes very dry in winter and early spring. In addition to Spartina other tall layer species include Aster squamatus, Euphorbia serpens, Mikania periplocifolia and Setaria geniculata. The intermediate and lower layers vary from place to place, but on strongly halomorphic soils there is usually an intermediate layer of Chenopodium macrospermum and Salicornia ambigua and a low creeping ground layer of Distichlis spicata and Paspalum vaginatum. On more humid soils there is often just a lower layer of Paspalum lividum together with Echinochloa helodes, Leersia hexandra, Ludwigia peploides and Paspalidium paludivagum. In very wet areas, such as waterlogged depressions, Spartina argentinensis can be replaced by Spartina densiflora, while in small often-circular flooded depressions the tall grass Paspalum intermedium can become dominant. Other halophytic species that may be encountered here include Cortaderia selloana, Heliotropium curassavicum, Hymenoxis anthemoides and Sesuvium portulacastrum.


Chacoan Elyonurus Savannas

Also within the Santafesiaian Chaco, but on better-drained soils, are savannas characterized by an upper herbaceous layer of Elyonurus muticans accompanied by Chloris canterae, Pterocaulon subvirgatum and Setaria geniculata. Typical of the lower herbaceous layer is Cynodon dactylon together with Cienfuegosia drummondii, Eryngium coronatum and Gamochaeta subfalcata. In places there is a dense shrub layer of the endemic or near endemic Tessaria dodoneaefolia (Asteraceae). Trees, on the other hand, are vary sparse, but may include some typical Chaco species such as Geoffroea decorticans and Prospis affinis.

Further information required.



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