Tree Community Change across 700 km of Lowland Amazonian Forest from the Andean Foothills to Brazil

Abstract

We describe patterns of tree community change along a 700‐km transect through terra firme forests of western Amazonia, running from the base of the Andes in Ecuador to the Peru–Brazil border. Our primary question is whether floristic variation at large scales arises from many gradual changes or a few abrupt ones. Data from 54 1‐ha tree plots along the transect support the latter model, showing two sharp discontinuities in community structure at the genus level. One is located near the Ecuador–Peru border, where the suite of species that dominates large areas of Ecuadorean forest declines abruptly in importance to the east. This discontinuity is underlain by a subterranean paleoarch and congruent with a change in soil texture. A second discontinuity is associated with the shift from clay to white sand soils near Iquitos. We hypothesize that the first discontinuity is part of an edaphic boundary that runs along the Andean piedmont and causes a transition from tree communities preferring richer, younger soils near the base of the Andes to those preferring poorer, older soils farther east. Because the floristic changes observed at this discontinuity are conserved for large distances to the east and west of it, the discontinuity is potentially key for understanding floristic variation in western Amazonia. The significant floristic turnover at the Ecuador–Peru border suggests that the only large protected area in the region—Ecuador's Yasuní National Park—is not adequate protection for the very diverse tree communities that cover vast areas of northern Peru.

Volume and Geographical Distribution of Ecological Research in the Andes and the Amazon, 1995–2008

“…While this landscape diversity helps reduce the scientific bias caused by researchers' focus on these sites, it would be useful to know what proportion of the Amazon basin, and which specific parts of the Amazon basin, share the landscape features of eastern Ecuador, southeastern Peru, and central Brazil, and thus to what degree results at these sites can be extrapolated to the larger surroundings. For example, while tree communities in the Peruvian hotspot are very similar to those in a large neighboring watershed [31], tree communities in the Ecuadorean hotspot can be strikingly different from those a short distance across the border in northern Peru [32].…”

Patterns of Plant Species Richness Within Families and Genera in Lowland Neotropical Forests: Are Similarities Related to Ecological Factors or to Chance?

“…However, stochastic processes seem to play a minor but significant role, given that the most species rich genera were similar between close-by areas, as predicted by neutral models. Our findings and an accumulating body of evidence show that forest composition does change along environmental gradients (e.g., Bohlman et al, 2008;Coronado et al, 2009;Engelbrecht et al, 2007;Pitman et al, 2008: Tuomisto, 2006, in spite of the occurrence of widely distributed species along Neotropical forests (Bohlman et al, 2008;Condit et al, 2002). This emphasizes the relevance of protecting in areas of high human preference, because they are usually located in particular ecological settings and floristic composition.…”

Inventario De Cumalas (Myristicaceae) en La Amazonía Peruana

“…Este patrón es similar a la distribución espacial de diversidad arbórea en el Perú, con valores de diversidad alta en el norte y menores valores en el sur (Ter Steege et al, 2003). La alta riqueza de especies podría estar relacionado a la gran variación edáfica y geológica encontrada en el norte del país, que genera también una alta variación en las tasas de recambio de especies (Pitman et al, 2008;Kalliola & Puhakka, 1993).…”

“…En la Amazonía peruana esta familia está representada principalmente por árboles (raro arbustos), dióicos (algunos monoicos), con hojas simples alternas, exudados que oxidan en colores translúcidos a rojizo o amarillento, con olores fuertes en la corteza interna, inflorescencias en fascículos o racimos, cimas, cabezuelas o panículas de fascículos; flores unisexuales, actinomorfas, apétalas, perianto gamotépalo, ovario súpero; frutos drupa dehiscente o cápsula (Warburg, 1897;Smith 1937;Cronquist, 1988;Spichiger et al, 1989;Gentry, 1993;Vásquez, 1997;Ribeiro et al, 1999;Ayala, 2003;Amasifuen & Zárate, 2005). La importancia ecológica de la familia radica en que varias de sus especies son abundantes en los bosques de la Amazonía peruana, y esta generalmente reportada entre las diez familias más abundantes (Terborgh & Andresen, 1998;Haugaasen & Peres, 2006;Wittmann et al, 2006;Pitman et al, 2008). También son micro-hábitat de diversos organismos vivos, desde aves, reptiles, insectos y hasta arácnidos, quienes encuentran en la arquitectura peculiar de este grupo de árboles un lugar especial donde habitar.…”