(, from

Old Tupi Old Tupi, Ancient Tupi or Classical Tupi () is a classical Tupian language which was spoken by the indigenous Tupi people of Brazil, mostly those who inhabited coastal regions in South and Southeast Brazil. In the words of Brazilian tupinol ...

: "root forest") is a word used in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

for blackwater-flooded forests in the

Amazon biome The Amazon biome () contains the Amazon rainforest, an area of tropical rainforest, and other ecoregions that cover most of the Amazon basin and some adjacent areas to the north and east. The biome contains blackwater river, blackwater and whitewa ...

. These forests and similar swamp forests are seasonally inundated with freshwater. They typically occur along the lower reaches of

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s and around freshwater lakes.

Freshwater swamp forests Freshwater swamp forests, or flooded forests, are forests which are inundated with freshwater, either permanently or seasonally. They normally occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are foun ...

are found in a range of

climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...

zones, from

boreal Boreal, northern, of the north. Derived from the name of the god of the north wind from Ancient Greek civilisation, Boreas (god), Boreas. It may also refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernand ...

through

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

. In the

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

of Brazil, a seasonally

whitewater Whitewater forms in the context of rapids, in particular, when a river's Stream gradient, gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that foam, froths, making t ...

-flooded forest is known as a várzea, which is similar to in many regards; the key difference between the two habitats is in the type of water that floods the forest.

Characteristics

is primarily characterized by seasonal inundation caused by abundant rainfall; in some areas, trees can be submerged for up to 6 months of the year. These ecosystems are relatively open and feature over 30%

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...

cover with an average canopy height ranging from ; sparse measurements of trees can reach . Tree composition includes a varied mixture of leaf types and seasonality. Development of tree communities within the freshwater swamp forests rely heavily on microtopography and flooding intensity. Swamp forests can have harsh environments, in which only a few adapted species are able to sustain life or dominate over other tree species. One of the tree species mostly found in freshwater swamp forests are

legume Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...

trees, in which most swamp forests have high single legume species populations. Legume trees in these forests are thought to be abundant in

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

, which is most common in waterlogged locations and is thought to be a favorable trait when experiencing seasonal and/or constant waterlogging. Freshwater swamp forests can be classified into two categories of forested

wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

s, which are permanently and periodically flooded forests. It is possible to find these two types because of the high microtopographic variation. Due to these topographic differences, tree communities are delimited and have a distribution over small continuous areas. These forests may be able to sustain a large number of

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

and

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

species, however,

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

varies between wetland ecosystems and the

species richness Species richness is the number of different species represented in an community (ecology), ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the Abundance (ecology), abunda ...

of the freshwater swamp forests is not entirely known. As for plant species, these forests have a lower diversity compared to other types of forests, such as the '' terra firme'', in South America.

Soil chemistry

forests are characterized by sandy

acidic soil Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the nega ...

s that have a low nutrient content. The color and acidity of the water is due to soil organic molecules called humic substances (e.g. humic acid, fulvic acid) that are dissolved in the water. The acidity from the water translates into acidic soils. They are the more nutrient poor than a comparable várzea forest. They also "carry less suspended inorganic elements and contain elevated concentrations of dissolved organic material such as humic and fulvic acids". Therefore, forests support comparatively less life and the environment found within these areas tend to lack species diversity and animal

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

. Várzea forest soils have high nutrient contents because they receive a transport of high sediment loads from the whitewater rivers. In contrast, forests do not receive this seasonal influx of sediments which explains the nutrient poor soils. However, they do have the highest

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

concentrations out of comparable várzea and terra firma forest soils. Nevertheless, the seasonal inundation of the soils leads to

anoxic Anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of dissolved ox ...

conditions which limits plant growth.

Flora

and other flooded forests typically display a lower diversity of plants than that seen in terra firma forests. Similar to other forests found throughout the tropics, it is common to observe only a few dominant tree species Distribution of trees and other plants is highly dependent on inundation tolerances of species causing a non-random distribution of plants where more flood-tolerant species are found at lower elevations and less flood-tolerant species are found on higher ground.

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

(or Leguminosae) and

Euphorbiaceae Euphorbiaceae (), the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of Euphorbia, the type genus of the family. Most spurges, such as ''Euphorbia paralias'', ar ...

are the dominant families of plants observed in forest.

Seed dispersal

Tree species adapted to seasonal inundation have adapted to maximize

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

production during periods of flooding in order to take advantage of newly available

seed dispersal In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...

methods. Fish consume nearly all fruit that fall into the water, and species that are unable to digest the seeds eventually excrete and disperse them into the water. Dispersal by other vectors such as birds and

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes. Thus monkeys, in that sense, co ...

s is secondary to that of fishes in . An important factor in seed survival is the presence of

seed predator Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source,Hulme, P.E. and Benkman, C.W. (2002) "Granivory", pp. 13 ...

s. Fishes that lack the strong jaws found in

characin Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationsh ...

s, such as

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

, digest the fleshy material of the fruit while the seeds pass through the gut unharmed. Because many catfishes are bottom-feeders, they are critical dispersers for seeds that sink upon entering the water.

Fauna

Diversity of terrestrial wildlife and fishes in is highly influenced by flooding. During periods of inundation, vast numbers of aquatic species migrate into the flooded forest in search of food. Fish populations are highest during maximum fruiting periods and

river dolphins River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant rive ...

and

giant otter The giant otter or giant river otter (''Pteronura brasiliensis'') is a South American carnivorous mammal. It is the longest member of the weasel family, Mustelidae, a globally successful group of predators, reaching up to . Atypical of mustel ...

s move in to prey upon them. Compared to terra firma forests, features lower nutrients and favors slow-growing plants with low fleshy fruit production, which has resulted in a lower diversity and abundance of animals. Larger terrestrial mammals have varied strategies of dealing with flooding:

red brocket deer The red brocket (''Mazama americana'') is a species of brocket deer from forests in South America, ranging from northern Argentina to Colombia and the Guianas. It also occurs on the Caribbean island of Trinidad (it also occurred on the island of ...

and

collared peccaries The collared peccary (''Dicotyles tajacu'') is a peccary, a species of artiodactyl (even-toed) mammal in the family Tayassuidae found in North, Central, and South America. It is the only member of the genus ''Dicotyles''. They are commonly ref ...

move into islands and shift diet from fruit to browsing woody plants. White-lipped peccaries and

tapirs Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...

are largely unaffected by seasonal inundation; both species take advantage of the greater abundance of fruit during these times. White-lipped peccaries migrate between flooded and dry areas and tapirs are highly capable swimmers.

Arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

mammals such as monkeys tend to be lower in species richness compared to terra firma forests due to the decrease in tree diversity and the resulting lack of variety of suitable food types. A lower population density of birds also reflects the lack of nutrients found in forests. For example, within

Jaú National Park The Jaú National Park () is a national park located in the state of Amazonas, Brazil. It is one of the largest forest reserves in South America, and part of a World Heritage Site. Location The name "Jaú" comes from that of one of the largest ...

, 247 species of birds are found in terra firma forests; 121 of those species are limited to that habitat. Within neighboring forests, 194 species of birds are found; of those, just 58 are restricted to .United Nations Environment Programme-World Conservation M. "Jaú National Park, Brazil." Jaú National Park, Brazil. The Encyclopedia of Earth, 17 Nov. 2008. .

Human occupation and use

Native Amazonians have been using and modifying the forests in which they have lived for thousands of years. Several studies suggest that the presence of nutrient-rich " black earth" in typically nutrient-poor environments indicates intense fertilization and burning of these areas. Black earth is a modified soil characterized by high nutrient content from highly stable organic matter and high levels of phosphorus. The highly fertile soils and the openness of these areas confirm that the native Amazonians have been using these fields for agriculture. However, the Amazonians have not only used these areas for crops; they have used their agricultural lands as a place to hunt as well. Many animals (rodents, tapirs and deer) are attracted to these areas for food. The Amazonians produce a surplus so that the animals do not over-consume their food resource. Though, if the animals do start to deplete their crops, they will then harvest higher numbers of animals. Additionally, Amazonians consume fish as a main source of protein. Indigenous peoples understand that, while flooded, the forest serves as an essential feeding ground that increases fish abundance. Because of this, many protect forests from deforestation.

Conservation

The greatest threat to forests is the construction of

hydroelectric dam Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

s on

tributaries A tributary, or an ''affluent'', is a stream or river that flows into a larger stream ('' main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which the ...

of the Amazon river; when constructed, the dams will divert huge amounts of water and dramatically change the

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...

of the Amazon basin and its ecosystems. Because many flora within seasonally inundated forests are highly adapted to a particular flooding schedule, alterations in flood patterns and the creation of permanently flooded areas will induce higher rates of tree mortality. The loss of these trees will likely affect populations of

frugivorous A frugivore ( ) is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance ...

understory In forestry and ecology, understory (American English), or understorey (English in the Commonwealth of Nations, Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the Canopy (biology), forest ca ...

birds, such as the

blue-throated piping guan The blue-throated piping guan (''Pipile cumanensis'') is a species of bird in subfamily Penelopina of family Cracidae, the guans, chachalacas, and curassows. It is found in Bolivia, Brazil, Colombia, Ecuador, the Guianas, Peru, and Venezuela. ...

and some ''

Amazona Amazon parrots are parrots in the genus ''Amazona''. They are medium-sized, short-tailed parrots native to the Americas, with their range extending from South America to Mexico and the Caribbean. ''Amazona'' is one of the 92 genera of parrots t ...

'' parrots that are restricted to . Loss of habitat will cause migrations of species that will inevitably lead to higher

competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indi ...

in unaffected habitats and possibly local

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...

is also a large conservation concern because forests are characterized by slow tree growth due to low soil nutrient content and high soil acidity. Despite low nutrient availability, and other floodplain forests can be biodiverse with some partially

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

species. Due to soil chemistry and seasonal inundation, trees and other resources tend to grow back more slowly after harvest by humans than in other types of Amazonian forests, . Accordingly, forests cannot sustain timber harvest. For the future, forests should be fully protected from logging and deforestation because of the low

productivity Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proce ...

found in them. In protected areas, such as

, the lack of

indigenous Indigenous may refer to: *Indigenous peoples *Indigenous (ecology) In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often populari ...

inhabitants and a low population of rural families limits the potential for over-harvest of fish and

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

species. However, enforcement of harvest regulation is problematic when there are only three park rangers at the entrance to the park. In other unprotected areas that lack rangers, unregulated harvest of fauna by peoples that move into forests to hunt and fish may adversely affect future stocks. Approximately 3% of the Amazon's seasonally inundated forests are under protection within

national park A national park is a nature park designated for conservation (ethic), conservation purposes because of unparalleled national natural, historic, or cultural significance. It is an area of natural, semi-natural, or developed land that is protecte ...

s or

biological reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...

Notable areas

Freshwater swamp forests are distributed in multiple climate zones throughout the world, such as boreal, temperate, tropical and subtropic zones. They are found in the

Afrotropics The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean. It was formerly known as the Ethiopi ...

Australasia Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...

Indomalaya The Indomalayan realm is one of the eight biogeographic realms. It extends across most of South and Southeast Asia and into the southern parts of East Asia. Also called the Oriental realm by biogeographers, Indomalaya spreads all over the Ind ...

, and the

Neotropics The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeog ...

. However, they are most notably found in Amazonian areas. ;

Cantão Cantão is a tropical forest ecosystem located in the central Araguaia River, Araguaia river basin, the southeastern edge of the Amazon biome, in the Brazilian state of Tocantins. It is one of the biologically richest areas of the eastern Amazon, ...

: forests are one of the distinct natural communities found in the

Cantão State Park The Cantão State Park () is a state park in the state of Tocantins, Brazil. It protects the Cantão wetlands, an area of igapó flooded forest in the ecotone where the Amazon rainforest merges into the cerrado. Location The Cantão State Park i ...

. They offer a rich bird fauna that includes some habitat specialists due to the unique ecosystem the blackwater inundation provides. The trees in the bloom once the inundation season begins. They do this so they can drop their fruit into the water to be dispersed by the different fish taxa. ;

:The Jaú National Park was designated in 1980 and is the largest national park in the Amazon Basin and the second largest protected tropical forest. It is known for its high level of biodiversity and varying ecosystems within. The park protects the entire watershed of the Jaú River, which happens to be one of the best examples of a blackwater ecosystem where the water is colored by acidic decomposing organic matter. ;

Mamirauá Sustainable Development Reserve The Mamirauá Sustainable Development Reserve () in the Brazilian state of Amazonas (Brazilian state), Amazonas, near the city of Tefé, is a reserve near the village of Boca do Mamirauá. It includes mostly Amazon rainforest, Amazonian flooded f ...

:a near

Tefé Tefé, known in early accounts as Teffé, is a Municipalities of Brazil, municipality in the state of Amazonas (Brazilian state), Amazonas, northern Brazil. History As early as 1620 the Portuguese Carmelites could already boast of converts amo ...

, Brazil ; Anavilhanas Ecological Station :an ecological station that includes hundreds of islands in the Rio Negro