Included here is the Caribbean coast as far as the Sierra Nevada de Santa Marta, and south into the Cauca and Magdalena valleys. Moving south it extends from the Panama Canal, south and east into the wet and moist forests of Panama's Darién province, and then through the Chocó region of western Colombia and the moist forests along the west coast of Ecuador and into the dry forests of southern Ecuador and extreme northwestern Peru. This latter area is often called the Tumbesian Centre (after Tumbes department of Peru) but it is primarily centred on El Oro and Azuay provinces in southwest Ecuador and Tumbes and Piura departments in northwest Peru.

Tumbesian Ceiba trichistandra Forest

This largely lowland forest ranges from mainly deciduous to semi-evergreen. The bulbous character of the evergreen, dominant Ceiba trichistandra (Malvaceae) make these forests very distinctive and in the more deciduous stands spiny red-barked Erythrina velutina (Fabaceae) adds to the distinctiveness. Undisturbed forest usually has a closed canopy that can reach heights of 25 m but with certain trees reaching 35 m. The other main canopy trees in the mainly deciduous forests of Tambo Negro include Cochlospermum vitifolium (Bixaceae), Eriotheca ruizii (Malvaceae), Erythrina velutina (Fabaceae), Hura crepitans (Euphorbiaceae) and Tabebuia chrysantha (Bignoniaceae). A sub canopy of small trees and shrubs includes Achatocarpus nigricans (Achatocarpaceae), Albizia multiflora (Fabaceae), Armatocereus cartwrightianus (Cactaceae), Capparis heterophylla (Capparaceae), Carica parviflora (Caricaceae), Croton fraseri (Euphorbiaceae), Ficus americana (Moraceae), Guazuma ulmifolia (Sterculiaceae), Phyllanthus anisolobus (Phyllanthaceae), Pithecellobium excelsum (Fabaceae), Rauvolfia tetraphylla (Apocynaceae), Senna atomaria (Fabaceae), Trichilia hirta (Meliaceae), Triplaris cumingiana (Polygonaceae) and Urera baccifera (Urticaceae). The herb layer is draught deciduous and only conspicuous during the rainy season but contains few grasses. Annuals and geophytes like Adiantum raddianum, Brachiaria fasciculata, Coursetia caribaea and Talinum paniculatum represent much of the ground cover. The few grasses may include Andropogon bicornis, Aristida adscensionensis, Chloris virgata and Pennisetum occidentale. Cacti, orchids, and bromeliads like Guzmania monostachya, Pitcairnia prolifera, Vriesea espinosae and various species of Tillandra, dominate the epiphytes. Other epiphytes include Rhipsalis micrantha and Trichocentrum tigrinum, but overall the epiphytic flora although abundant is not particularly rich in species. Climbers are conspicuous and seem to include a high proportion of cucurbit taxa such as Apodanthera, Momordica and Sicyos.

Tumbesian Acacia Thorn-Forest

Tumbesian zone thorn-forest characterized by Acacia species such as A. macracantha and A. tortuosa can replace other natural forests when they have been heavily degraded, but they are also thought to occur naturally on the lower slopes of the Tumbesian zone. These normally form open stands between 5-10 m tall and are largely deciduous. Common trees include Bursera graveolens (Burseraceae), Caesalpinia corymbosa (Fabaceae), Capparis mollis (Capparaceae), Muntingia calabura (Muntingiaceae), and where there is some groundwater influence Celtis iguanea (Cannabaceae) and Zizyphus piurensis (Rhamnaceae). Typical shrubs are Capparis cordata (Capparaceae), Cercidium praecox (Fabaceae), Cereus macrostilbas (Cactaceae), Cryptocarpus pyriformis (Nyctaginaceae), Encelia canescens (Asteraceae), Galvezia limensis (Plantaginaceae), Grabowskia boerhaviifolia (Solanaceae), Isocarpus microcephala (family?), Maytenus orbicularis (Celastraceae), Mimosa acantholoba (Fabaceae), Parkinisonia aculeata (Fabaceae) and Vallesia dichotoma (Apocynaceae). The deciduous herb layer develops into a dense, lush and fairly high structure during the rainy season. The main species include grasses and forbs such as Anthephora hermaphrodita (Poaceae), Aristida adscensionensis (Poaceae), Bouteloua disticha (Poaceae), Chloris virgata (Poaceae), Heliotropium angiospermus (Boraginaceae), Luffa operculata (Cucurbitaceae), Nicandra physaloides (Solanaceae), Schizoptera trichotoma (Asteraceae) and Sicyos chaetocephalus (Cucurbitaceae).

Magdalena Dry Forest

Located around the upper Magdalena River area in a flat inter-Andean valley these dry forests grow to heights of no more than about 15 m, and many of the trees have a characteristic umbrella shape. Typical trees and bushes include Acacia farnesiana, Bulnesia carrapo, Capparis odoratissima, Fagara pterota, Maclura tinctoria, Prakinsonia aculeata, Prosopis juliflora and the local endemic Pithecellobium bogotense (Fabaceae). Intermixed with the woody vegetation are various characteristic cacti species like Acanthocereus humilis, Pilosocereus colombianus and Stenocereus griseus many of which have very limited geographical distributions. Other local endemics include Amaria petiolata (family?), Cattleya trianaei (Orchidaceae) the national flower of Colombia, and Steriphoma colombiana (Capparaceae).


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