Várzea forest | ecology | Britannica (original) (raw)
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Amazon basin
In Amazon River …river and its tributaries, called várzeas (“floodplains”), are subject to annual flooding, with consequent soil enrichment; however, most of the vast basin consists of upland, well above the inundations and known as terra firme. More than two-thirds of the basin is covered by an immense rainforest, which grades into dry… Read More
In Amazon basin: Amazon basin ecosystems …lowland forests are divided into _várzeas_—i.e., forested areas inundated annually by white water, which deposits suspended sediment on floodplains that add to their fertility—and _igapó_—i.e., forests flooded annually by black water (in which tannins and humic acid cause the water to appear darker and increase its acidity) that contain slow-growing… Read More
In Amazon River: Soils of the Amazon River …potential of the annually flooded várzea areas is great. Their soils do not lack nutrients, since they are rejuvenated each year by the deposit of fertile silt left as the waters recede, but their usage for agricultural purposes is limited by the periodic inundations. It is estimated that these valuable… Read More
description
In Brazil: Amazon lowlands …of annually flooded plains (várzeas) separates the Guiana Highlands to the north from the Brazilian Highlands to the south. The várzeas fan out again as the watercourse approaches the Atlantic, but no delta extends into the ocean. The basin’s most widespread topographical features are gently undulating hills called terra… Read More
In plant: Plant geography …known by the Portuguese word várzea. Trees in this zone survive flooding for several weeks annually and provide the basis of a food web that includes fish adapted for grazing on tree fruits and seeds. The grazing fish possess large flat molars adapted for masticating seeds and other coarse organic… Read More
role of electric eels
In electric eel: Physical features …white-water flooded forest known as varzea. In one fish survey of a typical varzea, electric eels made up more than 70 percent of the fish biomass. Electric eels also eat fruit that falls from trees whose canopies hang over rivers. Consequently, they aid in seed dispersal via defecation. ( Read More
