Grasses in the canarana areas include Echinochloa and Hymenachne species, with tall grasses along the river margin such as Gynerium sagittatum, Paspalum repens and Echinocloa polystachya. Other trees that feed the fruit-eating fish that enter the forest during flood periods are the yellow mombim ( Spondias mombim), socoró ( Mouriri ulei) and tarumã ( Vitex cymosa). The economically valuable palms Astrocaryum jauari and Mauritia flexuosa are common on the floodplain. Tree species that grow only in wetlands include Virola surinamensis, Calycophyllum spruceanum and Açaí palm ( Euterpe oleracea). There are some palms, and often a dense understory of plants in the genus Heliconia and families Zingiberaceae and Marantaceae. Trees in the várzea are usually shorter than on terra firme, with a canopy of up to 25 metres (82 ft). Typically there are fewer tree species in the várzea than on terra firme, although many trees are common to both environments. The main vegetation types are aquatic vegetation, permanent swamp vegetation, succession vegetation and forest mosaics. The ecoregion is in the Neotropical realm and the tropical and subtropical moist broadleaf forests biome. The Köppen climate classification is "Af": equatorial, fully humid.Īverage monthly temperatures range from 23 to 32 ☌ (73 to 90 ☏) with an annual average of 28 ☌ (82 ☏).Īverage annual rainfall in the east is less than 2,000 millimetres (79 in), while in some parts of the Madeira in the west it exceeds 2,500 millimetres (98 in). The area behind the levees holds canarana grassland and lakes that expand and contract with the flood cycle. Typically the levees are relatively high, formed by the deposit of sediments along the river margins.īehind them the land slopes down, flattens out and then rises to the terra firme forest. These landscape elements support diverse vegetation, predominantly seasonally flooded tropical evergreen rainforest. The river course through the floodplain constantly shifts over time, creating oxbow lakes, levees, meander swales and bars. The river waters, loaded with sediment, rise by 6 to 12 metres (20 to 39 ft) each year, flooding the land for as long as eight months. The annual floods renew the sediments, making very rich soils compared to the higher terra firme on either side of the várzea. The soils are fertile sediments formed in the present Holocene epoch, carried down from the Andes. Physical Įlevations range from 15 metres (49 ft) in the east, where the Tapajós meets the Amazon river, to 80 metres (260 ft) on the Madeira. The Gurupa várzea is downstream along the Amazon. The Purus várzea is upstream along the Solimões and Purus rivers and their tributaries. The Purus-Madeira moist forests lie to the west of the Madeira and the south of the Amazon. The ecoregion adjoins the Madeira-Tapajós moist forests to the southeast and the Uatuma-Trombetas moist forests and Japurá-Solimões-Negro moist forests to the north. Major population centers in or near the ecoregion are Manaus, Itacoatiara, Coari and Óbidos. The várzea forests of this ecoregion extend along the low, seasonally flooded rivers of the central and lower basin of the Amazon River, including a large part of the Madeira River basin, the mouth of the Purus River, tributaries of these rivers and an isolated patch of várzea along the Mamoré River between Bolivia and Brazil. The Monte Alegre várzea (NT0141) is an ecoregion of seasonally flooded várzea forest along the Amazon River in the Amazon biome.
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