Purus-Madeira moist forests


The Purus-Madeira moist forests is an ecoregion in the central Amazon basin. It is part of the Amazon biome.
The ecoregion covers a stretch of flat and relatively infertile land between the Purus and Madeira rivers, extending to the Solimões River in the north. It is isolated from other regions by the seasonally flooded várzea forest along these rivers, and has a high degree of endemism among its flora and fauna.
The natural environment is relatively intact.
The BR-319 highway was built along the length of the ecoregion in the early 1970s, but rapidly deteriorated and is now closed.

Location

The Purus-Madeira moist forests ecoregion lies to the east of the Carauari arch, an ancient uplift zone in Brazil.
The ecoregion stretches from southwest to northeast between the Purus River to the west and the Madeira River to the east, both tributaries of the Solimões River.
In the south it is crossed by the Igapó-Açu River, Ipixuna River, Itaparaná River, Mucuim River, and Jari River.
The large rivers that separate the ecoregion from surrounding regions prevent many species from migrating from or to other regions, making a distinctive environment with various endemic species.
The Purus-Madeira moist forests are bounded by the Purus várzea ecoregion along the Purus and the Monte Alegre várzea along the Solimões and Madeira.
The Madeira-Tapajós moist forests lie on the east shore of the Madeira.
To the south there are stretches of Iquitos várzea in the Southwest Amazon moist forests.

Physical

The ecoregion covers an almost entirely flat area of in the lower Amazon basin.
The plain holds large meandering rivers that have formed many oxbow lakes, and a great many small streams, all subject to annual flooding.
Elevations range from.
It is within the low Amazon Basin, an area of soft sediments that emerged from five to two million years ago.
Soils are acidic and low in nutrients, mostly sandy podzols or hydromorphic clay soils.

Ecology

The ecoregion is in the Neotropical realm and the tropical and subtropical moist broadleaf forests biome.

Climate

The Köppen climate classification is "Am": equatorial, monsoonal.
Average temperatures range from with a mean of.
Temperatures are fairly constant throughout the year.
Average annual precipitation is.
Precipitation is lowest in July with an average of and highest in March with an average of.

Flora

Most of the vegetation is seasonally flooded tropical lowland rainforest.
The flora have high biodiversity and endemism.
In the north the forest is dense with a canopy of and emergent trees of up to.
There is a dense understory.
In the south the canopy is more open and the understory less dense.
In the extreme south the moist forest meets patches of wooded savanna.
As with other forests of the Amazon basin the main families are Fabaceae, Sapotaceae, Lecythidaceae, Moraceae, Chrysobalanaceae, Lauraceae and Myristicaceae.
The most common species are Eschweilera alba, Eschweilera odora, Pouteria guianensis, Vantanea guianensis, Ragala sanguinolenta, Licania apetala and Iryanthera ulei.
Four common species of palm are Astrocaryum vulgare, Oenocarpus bataua, Attalea maripa, and Socratea exorrhiza.
The palm-like Spathelia excelsa fruits once and then dies.
Couma utilis provides edible fruit.
The Physocalymma scaberrim is a typical emergent with red hardwood timber used in furniture.

Fauna

There is diverse fauna with many endemic species.
165 species of mammals have been recorded, of which over 80 are bats.
Primates include the bare-eared squirrel monkey, white-fronted capuchin, brown woolly monkey, and five species of titi monkey, of which Hershkovitz's titi, ashy black titi, and collared titi are endemic.
Other mammals include Hoffmann's two-toed sloth, brown-throated sloth, silky anteater, southern tamandua, giant anteater, collared peccary, jaguar, cougar, red brocket, gray brocket, and South American tapir.
Endangered mammals include Peruvian spider monkey, white-cheeked spider monkey and giant otter.
Green iguana and tegus lizards are common.
Snakes include fer-de-lance, palm pit-vipers, coral snakes, bushmasters and boa constrictors.
572 species of birds have been recorded including migrant toucan, Amazon parrot, and macaw.
Resident birds included tanagers, woodcreepers, resplendent quetzal, 15 species of curassows, and tinamous.
Endangered birds include wattled curassow, green-thighed parrot and red-necked aracari.

Status

The World Wildlife Fund classes the ecoregion as "Relatively Stable/Intact".
Most of the environment is undamaged, apart from the south.
A paved road was built along the length of the region from Humaitá to Manaus, but it proved impossible to maintain and was closed.
The Trans-Amazonian Highway crosses the southwestern end of the region from Humaitá to Lábrea and has caused deforestation to create pasturage and agricultural fields.
The southern area is threatened by controlled and uncontrolled fires.
Mining in the upper sections of the Purus and Madeira rivers causes pollution and habitat destruction.
During the period from 2004 to 2011 the ecoregion experienced an annual rate of habitat loss of 0.32%.
Global warming will force tropical species to migrate uphill to find areas with suitable temperature and rainfall.
Low, flat ecoregions such as the Purus-Madeira moist forests are extremely vulnerable.