Amazon landforms and soils in relation to biological diversity

Abstract

-Thirteen main landform units are distinguished for the whole of the forested planalto, and in the areas of relict valleys, in view of the prolonged geomorphological stability Key-words: Amazon, major landforms, tropical soils, floristic biodiversity. Paisagens Maiores da Amazônia e seus Solos em Relação com a BiodiversidadeRESUMO -Foram distinguidas treze unidades de paisagens maiores, em toda região Amazônica florestada, cada unidade com padrão de solos e estrutura de cobertura vegetal específica. Estas unidades de paisagem-solos-vegetação foram delineadas num mapa geral da região e ilustradas por um corte transversal esquemático. A diversidade florística, do tipo gamma, deve ser a mais alta no complexo paisagístico da Selva Alta, bordeando a Cordilheira Andina; nas terras firmes colinosas dos escudos cristalinos; no complexo de inselbergs, e no variante eutrico das terras firmes sedimentárias ocidentais. Estima-se que o endemismo seja mais alto nas planícies arenosas, e em partes dos complexos de chapadões e de inselbergs. Especiação, ligada com o conceito de refúgios florestais, é provavelmente mais alta nos chapadões de areniscos antigos, nas extensões do planalto Amazônico, e nas áreas de vales relictos, considerando a estabilidade geomorfológica prolongada destas unidades.Palavras-chave: Amazônia, unidades de paisagem; solos tropicais; biodiversidade florística 1 Ά preliminar version of this text appeared in ISRIC Annual Report over 1990, Wageningen, the Netherlands. Updating and digitizing of the coloured map took place in 1998. The digital version can be obtained separately from t 2 Consultant GTZ/PPG7/IPAAM; Manaus, Am. Brazil;

Soil-induced impacts on forest structure drive coarse woody debris stocks across central Amazonia

“…Mean annual precipitation in this area varies from 2155 to 2624 mm (WorldClim; Hijmans et al 2005). The soils are predominantly Plinthosols and Gleysols (Sombroek 2000), generally having varying degrees of soil water saturation and anoxic conditions. Soil physical structure is generally restrictive to root growth, with very high bulk density in the subsoil, and thus these soils have varying degrees of hardness and effective soil depth.…”

“…Soil physical structure is generally restrictive to root growth, with very high bulk density in the subsoil, and thus these soils have varying degrees of hardness and effective soil depth. Subsoil layers that limit root penetration are frequent and vary from 30 to 100 cm in depth (RADAMBRASIL 1978;Sombroek 2000). In all sites, we sampled a total of 45 plots deployed in nine site clusters, the clusters being at distances between 40 and 60 km apart (Figure 1).…”

“…The forests south of the Rio Amazonas represent a vast, but poorly studied region in central Amazonia, both in terms of vegetation and soil. Broadly, this region ( Figure 1) is characterised by hydromophic soils (RADAMBRASIL 1978;Sombroek 2000) of poor physical structure , in contrast to soils north of Manaus which are dominated by welldrained deep soils. This region is also expected to have large variation in above-ground biomass (AGB) (IBGE 1997).…”

Geochemical Signature of Amazon Tropical Rainforest Soils

“…Within the Amazon rainforest, several phytoecological units occur but are relatively poorly defined (Kricher, 1999). Amazon speciation, with large floristic diversity and areas of endemism, may be a consequence of the variety and distribution of soils (Sombroek, 2000;Ruokolainen et al, 2007;ter Steege, 2010;Guimarães et al, 2013), climatic variables (Clarke and Gaston, 2006), geographical barriers (Hunter Jr, 1999), and periodical disturbances that reduce dominance by species and induce competition (Collins et al, 1998). But in Brazil, these forests are home to 897 thousand native (indigenous) people who sustain themselves through subsistence agriculture, hunting, and fishing, and they are directly affected by contamination (IBGE, 2013).…”

Landform and landscape mapping, French Guiana (South America)

“…Geomorphology remains underused in tropical countries, mainly because geomorphologic maps are difficult to produce at a regional scale due to the extended forest cover, insufficiently accurate geological and topographical data, cloud cover on satellite images, and poor field accessibility for data collection and validation. This is particularly true in vast forest areas that consist of gently undulating relief such as the Guiana shield and the Amazon and Congo basins where local and continental geomorphologic information is lacking (Sombroek, 2000).…”