Igapó
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Igapó (, from
Old Tupi Old Tupi, Ancient Tupi or Classical Tupi (also spelled as Tupí) is an extinct Tupian language which was spoken by the aboriginal Tupi people of Brazil, mostly those who inhabited coastal regions in South and Southeast Brazil. It belongs to the ...
: "root forest") is a word used in
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
for blackwater-flooded forests in the
Amazon biome The Amazon biome ( pt, Bioma Amazônia) 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 and white ...
. 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 flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
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 found ...
are found in a range of
climate Climate is the long-term weather pattern in an area, 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 meteorologic ...
zones, from
boreal Boreal may refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernander sequence of northern Europe, during the Holocene epoch *Boreal climate, a climate characterized by long winters and short, cool to mild ...
through
temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
and
subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
to
tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...
. In the
Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its 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 Bolivi ...
of Brazil, a seasonally
whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...
-flooded forest is known as a várzea, which is similar to igapó in many regards; the key difference between the two habitats is in the type of water that floods the forest.


Characteristics

Igapó 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 20–25 m; sparse measurements of trees can reach 33–36 m. 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 A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...
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 nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...
, 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 ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
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 Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
,
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
,
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
,
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
,
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
and
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
species, however,
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
varies between wetland ecosystems and the
species richness Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative a ...
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

Igapó 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 neg ...
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, igapó forests support comparatively less life and the environment found within these areas tend to lack species diversity and animal
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
. Várzea forest soils have high nutrient contents because they receive a transport of high sediment loads from the whitewater rivers. In contrast, igapó 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 with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
concentrations out of comparable várzea and terra firme forest soils. Nevertheless, the seasonal inundation of the soils leads to
anoxic The term 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 diss ...
conditions which limits plant growth.


Flora

Igapó and other flooded forests typically display a lower diversity of plants than that seen in terra firme 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 The Fabaceae or Leguminosae,International Code of Nomenc ...
(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 a genus in the family. Most spurges, such as ''Euphorbia paralias'', are herbs, but some, e ...
are the dominant families of plants observed in igapó 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 that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
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 the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...
s is secondary to that of fishes in igapó. 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.: "Relationshi ...
s, such as
catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...
, digest the fleshy material of the fruit while the seeds pass through the gut unharmed. Because many catfishes are
bottom-feeder A bottom feeder is an aquatic animal that feeds on or near the bottom of a body of water. Biologists often use the terms ''benthos''—particularly for invertebrates such as shellfish, crabs, crayfish, sea anemones, starfish, snails, bri ...
s, they are critical dispersers for seeds that sink upon entering the water.


Fauna

Diversity of terrestrial wildlife and fishes in igapó 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 riv ...
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 musteli ...
s move in to prey upon them. Compared to terra firme forests, Igapó 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 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 referred to as ...
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 pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inhabit ...
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 Animal locomotion, 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, but others are exclusively arboreal. Th ...
mammals such as monkeys tend to be lower in species richness compared to terra firme 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 igapo forests. For example, within
Jaú National Park The Jaú National Park ( pt, Parque Nacional do Jaú) is a National park (Brazil), national park located in the state of Amazonas State, Brazil, Amazonas, Brazil. It is one of the largest forest reserve in South America, and part of a World Herita ...
, 247 species of birds are found in ''terra firme'' forests; 121 of those species are limited to that habitat. Within neighboring igapó forests, 194 species of birds are found; of those, just 58 are restricted to igapó.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 igapó 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 igapó forests from deforestation.


Conservation

The greatest threat to igapó forests is the construction of
hydroelectric dam Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...
s on
tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or 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 drain the surrounding drainage b ...
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 environmental watershed sustainability. A practitioner of hydrology is calle ...
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 and ...
understory In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abov ...
birds, such as the blue-throated piping guan 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 igapó. 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, indivi ...
in unaffected habitats and possibly local
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
s.
Deforestation Deforestation or forest clearance is the removal 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. The most concentrated d ...
is also a large conservation concern because Igapó forests are characterized by slow tree growth due to low soil nutrient content and high soil acidity. Despite low nutrient availability, Igapó and other floodplain forests can be biodiverse with some partially
endemic Endemism is the state of a species being found 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 found elsew ...
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, igapó forests cannot sustain
timber harvest Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...
. For the future, igapó 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 proces ...
found in them. In protected areas, such as
Jaú National Park The Jaú National Park ( pt, Parque Nacional do Jaú) is a National park (Brazil), national park located in the state of Amazonas State, Brazil, Amazonas, Brazil. It is one of the largest forest reserve in South America, and part of a World Herita ...
, the lack of
indigenous Indigenous may refer to: *Indigenous peoples *Indigenous (ecology), presence in a region as the result of only natural processes, with no human intervention *Indigenous (band), an American blues-rock band *Indigenous (horse), a Hong Kong racehorse ...
inhabitants and a low population of rural families limits the potential for
over-harvest Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...
of fish and
turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
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 igapó 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, natural park in use for conservation (ethic), conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state dec ...
s or biological reserves.


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 Earth's eight biogeographic realms. It includes Africa south of the Sahara Desert, the majority of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the island ...
,
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologica ...
,
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 Indi ...
, and the
Neotropics The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropics, tropical Ecoregion#Terrestrial, terrestrial ecoregions of the Americas and the entire South American temperat ...
. However, they are most notably found in Amazonian areas. *
Cantão Cantão is a tropical forest ecosystem located in the central 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, with over 700 ...
Igapó forests are one of the distinct natural communities found in the
Cantão State Park The Cantão State Park ( pt, Parque Estadual do Cantão) 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. Loca ...
. They offer a rich bird fauna that includes some habitat specialists due to the unique ecosystem the blackwater inundation provides. The trees in the igapó 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. *
Jaú National Park The Jaú National Park ( pt, Parque Nacional do Jaú) is a National park (Brazil), national park located in the state of Amazonas State, Brazil, Amazonas, Brazil. It is one of the largest forest reserve in South America, and part of a World Herita ...
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 ( pt, Reserva de Desenvolvimento Sustentável Mamirauá) in the Brazilian state of Amazonas, near the city of Tefé, is a reserve near the village of Boca do Mamirauá. It includes mostly Amazonian ...
- a 22,000-square-mile (57,000 km2) near
Tefé Tefé, known in early accounts as Teffé, is a municipality in the state of Amazonas, northern Brazil. Location Tefé is located about 525 km by air or 595 km by river to the west of Manaus on the south bank of the Rio Solimões (th ...
, Brazil * Anavilhanas Ecological Station - an ecological station that includes hundreds of islands in the Rio Negro


References


See also

*
Freshwater swamp forest 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 found ...
* Varzea *
Swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
{{DEFAULTSORT:Igapo Aquatic ecology Forests of Brazil