Towards an ecological classification of flooded savannas in Beni (Bolivia)

Abstract

Abstract.-Two main types of flooded savannas are identified in Beni, one of the most extensive areas of flooded savannas in the Neotropics: the floodable savannas of the bajíos and the floodable savannas of the semi-uplands. Independent classification methods done for both floristic inventories and soil sampling show a strong relationship between the content and availability of exchangeable bases in the soils and floristic composition of the plant communities. The grassy savannas on mesotrophic substrates which are rich particularly in Mg and Ca are characterized floristically by Thevetia amazonica and Acroceras zizanioides. On base-poor substrates, the floodable grassy savannas, as well as the tajibo savanna, are best represented floristically by Andropogon bicornis and Coelorachis aurita. A CCA carried out on this type of savannas revealed a primary distribution pattern of the plant communities along an Fe gradient, which can also be explained as a gradient of the duration of the flooding period.Key words : wetlands -grassy savanna -mineral nutrients -ecology -South America.Résumé.-Deux types principaux de savanes inondées ont été identifiés dans le Beni, une des plus grandes surfaces de savanes inondées des Néotropiques : les savanes inondables des basses terres et les savanes inondables des semihautes terres. Diverses méthodes de classification appliquées aux inventaires floristiques et aux échantillons de sols montrent une forte relation entre le contenu et la disponibilité des bases échangeables dans les sols et la composition floristique des communautés végétales. Les savanes herbeuses sur substrat mésotrophe qui sont particulièrement riches en Mg et Ca sont caractérisées par Thevetia amazonica et Acroceras zizanioides. Sur les substrats oligotrophes, les savanes herbeuses inondables, ainsi que la savane tajibo, sont dominées par Andropogon bicornis et Coelorachis aurita. L'analyse canonique des correspondances réalisée exclusivement sur savanes à sols oligotrophes montre un modèle de distribution des communautés le long d'un gradient de fer, qui peut aussi être expliqué comme un gradient de durée de la période d'inondation.Mots clés : zones humides -savanes herbacées -nutriments minéraux -éco-logie -Amérique du Sud.

The biogeographical kingdoms and regions of the world

“…The dominant species are Aspidosperma quebracho-blanco (white quebracho) and Schinopsis balansae (quebracho-colorado), S. lorentzii, Ceiba chodatii, C. speciosa, to which are added Copernicia alba, Geoffroea decorticans, Jodina rhombifolia, Libidibia paraguariensis, Myracrodruon balansae, Neltuma alba, N. kunzei, N. nigra, N. ruscifolia, Sarcomphalus mistol, Sideroxylon obtusifolium, Strombocarpa torquata Trithrinax campestris, etc. It is important to note the presence of extensive floodplain areas subject to various flooding regimes, particularly the "Gran Pantanal" located at the confluence of the Brazilian Mato Grosso, northern Paraguay, and western Bolivia, spanning the departments of Santa Cruz and Beni (Navarro-Sánchez & Ferreira, 2009;Navarro-Sánchez et al, 2010;Navarro-Sánchez, 2011) and covering a total extent of 340,000 km 2 .…”

BOVEDA, the Bolivian Vegetation Ecology Database: first stage, the Chacoan forests

“…Further data from past and current fieldwork conducted in areas of other South American countries including Argentina, Chile, Brazil, Venezuela and Ecuador are intended to be stored as well. The expectations of this database rest on two steps: the first extending over the next year will deal with including the raw data of works already published by us (Navarro et al 2005;Molina et al 2007;Navarro et al 2010;Navarro 2011;Molina et al 2016;Navarro and Molina 2019), while the second will then also include unpublished information from areas such as the inter-Andean dry valleys vegetation or hygrophytic vegetation such as High-Andean wetlands.…”

A novel biome concept and classification system based on bioclimate and vegetation – a Neotropical assay

“…extensive wetlands -Figure 2D -or vast special substrates such as rocks, serpentine or sands). Such landscapes are considered as azonal biomes (Walter 1973;Navarro et al 2010) are considered here a secondary biome because, although these biomes are human-altered, they currently occupy large areas (Faber-Langendoen et al 2014;Ellis 2015Ellis , 2020 and are also influenced by the bioclimate and altitudinal zonation (Table 2; Figure 3A-D).…”