Dominance and Distribution of Tree Species in Upper Amazonian Terra Firme Forests

Abstract

Amazonian forests are the largest and most diverse in the tropics, and much of the mystery surrounding their ecology can be traced to attempts to understand them through tiny local inventories. In this paper we bring together a large number of such inventories scattered across immense areas of western Amazonia in order to address simple questions about the distribution and abundance of tropical tree species in lowland terra firme forests there. The goal is to describe patterns of commonness and rarity at local (1 ha), landscape (∼104 km2), and regional (>106 km2) scales, and to fuse the results into a more complete picture of how tropical tree communities are structured. We present estimates of landscape‐scale densities for ∼1400 taxa, based on data from tree plots scattered over large tracts of terra firme forest in eastern Ecuador and southeastern Peru. A database of morphological, ecological, and other traits of >1000 of these species compiled from the taxonomic literature is then used to explore how species that are common in the inventories differ from species that are rare. Although most species show landscape‐scale densities of <1 individual/ha, most trees in both forests belong to a small set of ubiquitous common species. These common species combine high frequency with high local abundance, forming predictable oligarchies that dominate several thousand square kilometers of forest at each site. The common species comprising these oligarchies are a nonrandom subset of the two floras. At both sites a disproportionate number of common species are concentrated in the families Arecaceae, Moraceae, Myristicaceae, and Violaceae, and large‐statured tree species are more likely to be common than small ones. Nearly a third of the 150 most common tree species in the Ecuadorean forest are also found among the 150 most common tree species in the Peruvian forest. For the 254 tree species shared by the two data sets, abundance in Ecuador is positively and significantly correlated with abundance ∼1400 km away in Peru. These findings challenge popular depictions of Amazonian vegetation as a small‐scale mosaic of unpredictable composition and structure. Instead, they provide additional evidence that tropical tree communities are not qualitatively different from their temperate counterparts, where a few common species concentrated in a few higher taxa can dominate immense areas of forest. We hypothesize that most Amazonian forests are dominated at large scales by oligarchies similar in nature to the ones observed in Ecuador and Peru, and we argue that the patterns are more indicative of regulation of relative abundances by ecological factors than of nonequilibrium chance‐based dynamics. The paper concludes with a discussion of the practical applications of predictable oligarchies over large areas of unexplored forest.

Amazonian Rainforests and their Richness of Coleoptera, a Dominant Life Form in the Critical Zone of the Neotropics

“…Previously, when forest ecologists looked at the Amazon Basin they saw complexity, not pattern. After examining tree-distribution data more closely, however, Pitman et al (2001) found that the common trees formed predictable oligarchic hierarchies that were present across the complex landscape. In both their Ecuador and Perú plots, they found dozens of common species and hundreds of rare species.…”

Lecciones ecológicas de la historia amazónica: impacto diferencial del uso del suelo en las estructuras y biomasas aéreas de bosques secundarios en Napo, Ecuador

“…Luego de calcular la biomasa aérea de cada árbol, se transformaron los resultados a toneladas por hectárea. Finalmente, se compararon gráficamente los datos con los de los bosques amazónicos maduros de tierra firme reportados por Pitman et al (2001), Baker et al (2004), Pallqui et al (2014) para ilustrar cambios en la sucesión secundaria asociados a la historia de uso del suelo.…”

“…P(mad) = datos de Tambopata-Madre de Dios, Perú (Pallqui et al 2014; n = 9 parcelas). E,P(mad) = datos de Yasuní y Manu (Ecuador y Perú respectivamente) (Pitman et al 2001; n = 26 parcelas). Bo, Br, E, P(mad) = datos de Bolivia, Brasil, Ecuador y Perú (Baker et al 2004; n = 44 parcelas).…”

“…(b) Sugieren que la extracción durante la sucesión retarda la recuperación del área basal y la biomasa (compárese con Pitman et al 2001, Baker et al 2004y Pallqui et al 2014. Pero (c): la densidad puede recuperarse con cierta rapidez gracias a la colonización desde la matriz circundante y la formación de claros (comparando con Pitman et al 2001y Baker et al 2004. Todo eso puede ayudar a explicar por qué hay ecosistemas forestales tropicales cuyo recobro tarda 50-80 años (Martin et al 2014), en lugar de aprox.…”

“…4. ¿Qué tendencias de recuperación de la densidad de individuos, el área basal y la biomasa aérea a través de la sucesión secundaria, asociadas a la historia de uso del suelo, bosqueja este estudio, en combinación con otras investigaciones en bosques amazónicos maduros (Pitman et al 2001, Baker et al 2004, Pallqui et al 2014 Evaluación socioeconómica e histórica. Se obtuvieron y consultaron: una imagen de satélite Landsat 7 (ruta 9, fila 60, año 2012) y un mapa catastral de la zona estudiada Figura 1.…”