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Southwest Amazon moist forests are an ecoregion located in the Upper Amazon Basin. The region is characterized by a relatively flat landscape with alluvial plains dissected by undulating hills or high terraces. The biota of the southwest Amazon moist forest is very rich because of these dramatic edaphic and topographical variations at both the local and regional levels. This ecoregion has the highest number of both mammals and birds recorded for the Amazonian biogeographic realm: 257 with 11 endemic species for mammals and 782 and 17 endemics for birds. The inaccessibility of this region, along with few roads, has kept most of the habitat intact. Also, there are a number of protected areas, which preserve this extremely biologically rich ecoregion. ==Location and general description== The southwest Amazon moist forest region covers an extensive area of the Upper Amazon Basin comprising four sub-basins: (1) both the Pastaza-Marañon and (2) Ucayali River sub-basins drain into the Upper Amazon River in Peru; (3) the Acre and (4) Madre de Dios-Beni sub-basins drain to the east into the Juruá, Purus and Madeira Rivers; which, in turn, feed into the Amazon River lower down in Brazil.〔 The region is bisected north to south between Peru and Brazil by the small mountain range Serra do Divisor. It extends east to the edge of the Purus Arch, or ancient zone of uplift, in the southwestern area of the Brazilian State of Amazonas. It then extends southeast into northern Bolivia and in a narrow band south along the base of the Andes Mountains. Elevations range from in the west to on the eastern edge of the region. Because the ecoregion covers such a vast area, there are climatic, edaphic and floristic differences within it. Generally, the wetter and less seasonal northern forests ( of rain annually) share only 44 percent of the tree species with forests in the slightly drier, more seasonal southern region. This region receives from of rain annually, in different parts. Temperatures over the year range from . Landforms present in this region include the upland terra firme (non-flooded) mostly on nutrient-poor lateritic soils, ancient alluvial plains (mostly non-flooded) on nutrient-rich soils, and present alluvial plains (várzea, seasonally flooded) of super-rich sediments renewed with each annual flood.〔 Floristically, distinct lowland humid forest types occur on each of these landforms with the terra firme mature forests and late successional, seasonally flooded forest being the two major types. Permanent swamp forests are common on the alluvial plains. Pockets of nutrient-poor white sand soils are found here that host forests of lower height, a more open forest canopy, and lower alpha diversity, but with many endemics. The forests are mostly dense tropical rain forest, but some patches of open forest exist. At first glance, large areas may appear to be homogeneous dense forests with a canopy high with some emergent trees to towering above the canopy.〔 Structurally, this may be the case; however, the species composition reflects much the opposite: tree species variability reaches upwards to 300 species in a single hectare. There are a few exceptions to this high diversity, mainly where stands dominated by one or several species occur. The first are vast areas (more than ) dominated by the highly competitive arborescent bamboos ''Guadua sarcocarpa'' and ''Guadua weberbaueri'' near Acre, Brazil extending into Peru and Bolivia. Other monodominant stands include swamp forests of the economically important palms ''Mauritia flexuosa'' and ''Jessenia bataua''. In the north of the region, some of the best known plants yield products of commercial value, such as rubber (''Hevea brasiliensis''), mahogany (''Swietenia macrophylla''), balsam wood (''Myroxylon balsamum''), timber and essential oil (''Amburana acreana''), tagua nut (''Phytelephas microcarpa''), and strychnine (''Strychnos asperula'').〔 An area representative of the southern part of this region, in the north of Bolivia, hosts a seasonal humid high forest to with some emergents reaching in height and many buttressed trunks. The largest trees are ''Ceiba pentandra'', ''Poulsenia armata'', ''Calycophyllum spruceanum'', ''Swietenia macrophylla'', and ''Dipteryx odorata''. Other trees typical in this area are ''Calycophyllum acreanum'', ''Terminalia amazonica'', ''Combretum laxum'', ''Mezilaurus itauba'', ''Didymopanax morototoni'', ''Jacaranda copaia'', ''Aspidosperma megalocarpon'', ''Vochisia vismiaefolia'', ''Hirtella lightioides'', and ''Hura crepitans''. Palms include, among others, members of the genera ''Astrocaryum'', ''Iriartea'' and ''Sheelea'', ''Oenocarpus mapora'', ''Chelyocarpus chuco'', ''Phytelephas macrocarpa'', ''Euterpe precatoria'', and ''Jessenia bataua''. Lianas are common with about 43 species present. Many Amazonian species reach the southern limit of their distribution here. The Brazil nut tree (''Bertholletia excelsa'') is present in the south, but is likely not native this far west in Amazonia. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Southwest Amazon moist forests」の詳細全文を読む スポンサード リンク
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