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Várzea forest
Várzea forest is seasonal floodplain forest inundated by whitewater rivers that occurs in the Amazon River Basin.
==Description==
Along the Amazon River and many of its tributaries, high annual rainfall that occurs mostly within a rainy season results in extensive seasonal flooding of areas from stream and river discharge. The result is a 10–15 meter rise in water level, with nutrient rich waters.
Várzea forests can be split into two categories: low várzea and high várzea. Low várzea forests can be categorized by lower lying areas where the annual water column has an average height of more than 3 meters, where the period of flooding is greater than 50 days per year.〔 High várzea forests are categorized as the areas where the average annual water column is less than 3 meters high and flooding periods are less than 50 days per year.〔 Amazonian várzea forests are flooded by nutrient rich, high sediment white water rivers such as the Solimões-Amazon, the Purus, and Madeira rivers. This makes the várzea areas distinct from igapós, floodplains from nutrient poor black water.〔 The water level fluctuations that the várzea experiences result in distinct aquatic and terrestrial phases within the year. Amazonian white water river floodplains cover an area of more than 300,000 km2, and várzea forests cover approximately 180,000 km2 of the Amazon basin. 68% of the Amazonian river basin is located in Brazil, with the remaining areas located in Bolivia, Colombia, Ecuador, French Guiana, Peru, Suriname, and Guyana.〔 The várzea extends from this basin upward into the land before reaching slopes into the terra firme forests.
Várzea habitats are generally diverse, consisting of forests, grasslands, lakes, flooded fields, and swamps.〔 Approximately 75% of the várzea areas consist of dense canopy forests, with the other 25% being represented by the remaining habitats. Within the várzea, topographic variation leads to different flooding durations and severity, resulting in vegetation being separated where plants with different tolerances to flooding inhabit different areas.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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