White‐sand Ecosystems in Amazonia

Abstract

Vegetation on sandy soils, ranging from open grasslands and shrublands to closed‐canopy, thin‐trunked forests, can be found in patches throughout the Amazon. Despite variation in names, appearance, ecological correlates, and suggested origins, these ‘white‐sand ecosystems’ (WSE) share distinctive characteristics and biological communities. Here, in the first Amazon‐wide review of WSE, we review the variation in WSE and the factors underlying this variation. We present the most comprehensive Amazon‐wide map to date of WSE and calculate their total area. We find that WSE are still not completely mapped, and we use biological correlates as a proxy to indicate where white‐sand vegetation patches likely occur. Through our synthesis of the literature, we find that key factors, such as geologic origin, soil characteristics, hydrology, and fire regimes, vary widely and have differing impacts in different regions on vegetation structure and on floral, faunal, and fungal species composition. Although studies of WSE have increased dramatically in recent years, WSE in many parts of the Amazon remain understudied, and there is little synthesis of the interaction of factors across different areas. In response, we suggest priorities for future research. Finally, we find that WSE are inadequately protected and, where accessible, are regularly mined for sand, logged, or burned and cleared for agriculture. We argue that due to their island‐like distribution patterns and resultant complex metapopulation dynamics, their extremely slow recovery after disturbance, and their important contributions to basin‐wide diversity patterns and ecosystem services, WSE should be given special consideration in conservation efforts to ensure their persistence in Amazonia.

Soil-vegetation relationships and community structure in a "terra-firme"-white-sand vegetation gradient in Viruá National Park, northern Amazon, Brazil

“…Aside from the pedological and hydrological aspects that influence the adaptation and selection of species, fire also seems to play a relevant role in species structuring and distribution of the Arboreous Campinaranas (Adeney et al 2016). The few months of drought, coupled with excellent soil drainage, are enough to make the Arboreous Campinaranas, rich in herbaceous species, highly inflammable.…”

Biodiversity, threats and conservation challenges in the Cerrado of Amapá, an Amazonian savanna

“…However, further islands of savanna of varying size occur throughout the Amazon biome, known as Amazonian savannas (Carvalho and Mustin 2017;Prance 1996). The Amazonian savannas represent a distinct ecosystem within the large Amazonian region (see Prance 1996), different also from the white-sand ecosystems that further pepper the Amazon biome (see Adeney et al 2016). These Amazonian savannas have generally been under-studied (see Carvalho and Mustin 2017) and are highly threatened, principally as a result of land-grabbing and the advance of cultivation of grãos (grains and pulses, mainly soybeans and maize), plantations of exotic woody species (eucalyptus and acacia), and un-controlled fires (Barbosa et al 2007;Carvalho and Mustin 2017;Aguiar et al 2014).…”

Mapeo De Los Bosques Tipo Varillal Utilizando Imágenes De Satélite Rapideye en La Provincia Maynas, Loreto, Perú

“…Este tipo de bosque ha sido confundido por Josse et al (2007) y Encarnación et al (2015) con los bosques de palmeras sobre pantano (localmente conocidos como Aguajales) debido a su alta similitud mediante interpretación visual de imágenes satelitales de resolución espacial media como Landsat. Los varillales sobre arena blanca fueron reportados en varios estudios en los sectores de la Reserva Nacional Allpahuayo Mishana y las cuencas de los ríos Nanay, Pintuyacu y Chambira (Adeney et al, 2016;Álvarez et al, 2010;Fine et al, 2010;Gómez, 2006;Josse et al, 2007;Encarnación, 1993). Este estudio muestra la importancia de utilizar imágenes de satélite de alta resolución como las imágenes RapidEye, así como escalas de mayor detalle respecto a los trabajos anteriormente mencionados.…”