The Forests of the Upper Rio Negro (North-Western Amazon) and Adjacent South-Western Orinoco Basins: A Phytosociological Classification

Abstract

This chapter presents the first attempt at a phytosociological analysis of forests in the upper Rio Negro (north-western Amazon) and adjacent south-western Orinoco basins, based on both floristic composition and species relative dominance. The region harbors unique plant communities that thrive under very wet climatic conditions on oligotrophic soils, drained by (mostly) black, white, or clear water rivers. The floristic composition and classification of the vegetation types were determined using data from 226 inventory plots where all individuals of diameter at breast height (DBH) ≥ 2.5 cm were measured. A set of 1368 species corresponding to 387 genera and 94 families of vascular plants was used to perform a two-way indicator species analysis (TWINSPAN). We defined the phytosociological class Eperuo leucanthae—Eperuetea purpureae, composed of seven forest communities at association level and a larger group integrated by one undetermined association. There are two orders at the highest rank. The first order (Heveo guianensis—Eperuetalia purpureae) includes three alliances and six associations, and contains the forests that grow on sandy, acidic, and extremely leached soil substrate. The Oenocarpodo batauae—Eperuion leucanthae alliance comprises two typical upper Rio Negro associations: the Amazonian caatinga and the “yévaro” forests (Micrandro elatae-Micrandretum spruceii and Oenocarpodo batauae-Eperuetum purpureae). The second order (Goupio glabrae—Minquartiion guianensis) corresponds to forests drained by white and clear waters, growing on clay soils. Data on the floristic diversity and the main environmental factors that determine the structure and floristic composition of these plant communities are presented.

“Sábado víspera de la Santísima Trinidad (3 de junio de 1542)… ..vimos una boca de otro río grande á la mano siniestra, que entraba en el que nosotros navegávamos, el agua del cual era negra como tinta, y por esto le pusimos nombre del Río Negro, el cual corría tanto y con tanta ferocidad que en más de veinte leguas hacia raya en la otra abu, sin resolver la una con la otra” (Fr. Gaspar de Carvajal. Relación del viaje de Francisco de Orellana al río Amazonas—1541–1542).

“On some black-water rivers, such as the Pacimoni, the Atabapo, and the Rio Negro in some parts of its course, the breadth of inundated land is entirely clad with bushes and small trees of very equable height, on the skirts of which the Virgin Forest rises abruptly to a height more than twice as great. This is called by the natives ‘caatinga-gapo.’ Besides these differences of aspect, the natives will tell you there are other more intrinsic ones.” (Notes of botanist on the Amazon and Andes, Richard Spruce, 1908)

Appendices

Appendix 3.1: Phytosociological Classification and Description of the New Alliances and Associations of the Forest Communities in the Rio Negro Region

Phytosociological classification	Physiognomy and composition	Syntaxonomy	Ecology and distribution
ORDEN I 1. Parahancornio surrogatae Aldinion latifoliae all. Nov. (Figs. 3.5 and 3.6) Typus: Aldino latifolia - Terminalietum ochroprumnae (this study; Appendix 3.1 (this information is available in the following link: https://1drv.ms/f/s!AsgLjs_JMencgZsGYB0kltyDnwkilg). Lowlands forests of the Parahancornia surrogata - Aldina latifolia alliance Cover area: 81,621.43 km2 (Figs. 3.5 and 3.6)	The forest communities of this alliance are of medium to high stature (25–35 m tall), characterized by the presence of trees of: Apocynaceae, Euphorbiaceae, Lauraceae, Fabaceae, Malvaceae, Moraceae, Myristicaceae, and Sapotaceae	This alliance is defined on the basis of 24 samples that included 279 species, 166 genera in 62 families. This syntaxon is named with the elective species Parahancornia surrogata and the dominant legume species Aldina latifolia. Within the elective species are: Calophyllum brasiliense, Glandonia williamsii, Caraipa longipedicellata, Sloanea laurifolia, Hevea nitida, Mollia speciosa, Pachira nitida and Licania mollis. Other species can be found in Appendix 1. This alliance includes two new associations: Aldino latifoliae - Terminalietum ochroprumnae and Caraipo longipedicellatae - Micrandretum spruceii	The Parahancornia surrogata - Aldina latifolia alliance is found on slightly elevated positions in depressions, and on a sandy, somewhat poorly drained Entisols and spodosols. It is exposed to water-logging and also more susceptible to short droughts than other poorly or very poorly drained sandy soils, due to the shallow depth to the coarse sandy saprolite. This alliance is compound by forests on white sands, “terra firme,” and seasonally flooded forests with or without palm dominance.
1.1 Aldino latifoliae - Terminalietum ochroprumnae assoc. nov. (Figs. 3.5 and 3.6). Typus: Plot no. CC_130, TWINSPAN ID 69. Coordinates datum WGS84 LAT 3.6877, LON -67.4550. Altitude 89 m. Colombia. (Appendix 2; this information is available in the following link: https://1drv.ms/f/s!AsgLjs_JMencgZsGYB0kltyDnwkilg) Forests of terminalia ochroprumna and Aldina latifolia Cover area: 11,703.52 km2 (Figs. 3.5 and 3.6)	The forests of terminalia ochroprumna and Pachira nitida are medium to high in stature and density, composed by trees with a DBH average greater than 10 cm. In this association, the following species registered the largest height: Vochysia catingae (26.1 m), Parkia discolor (25.7 m), terminalia ochroprumna (21.3 m), Elaeoluma crispa (18 m), and Aldina latifolia (16 m). The species with the highest physiognomic expression (relativized units) are: Aldina latifolia (5.7%), Calophyllum brasiliense (5.6%), Hevea guianensis (5.1%), Pachira nitida (4.9%), Humiriastrum excelsum (3.3%), Leptabalanus wurdackii (3.1%), Elaeoluma crispa (2.9%) and Mollia lepidota (2.8%).	This association is defined on the basis of 7 samples that included 90 species, 61 genera in 27 families. The name of this syntaxon was based on the elective species, the legume Aldina latifolia and terminalia ochroprumna, the most dominant and exclusive species. In this association, Elaeoluma crispa was registered as exclusive species as well. Within the elective species are: Pachira nitida, Macrolobium multijugum, Mollia lepidota, Peltogyne paniculata, Swartzia sericea, Tachigali paniculata, Humiriastrum excelsum, and Leptobalanus apetalus. Other species can be found in the Appendix 3.1.	This vegetation community consists of low caatingas on white sand and seasonally flooded forests in black water. The forest of the association Aldino latifoliae Terminalietum ochroprumnae was determined based on seven (7) samples located in Colombia (i.g., along the Atabapo river in the border with Venezuela). Detailed information about these localities are found in Appendix 3.2.
1.2. Caraipo longipedicellatae -Micrandretum spruceii assoc. nov. (Figs. 3.5 and 3.6) Typus: Plot CC_153, TWINSPAN ID 92. Coordinates datum WGS84 LAT 3.0986, LON -67.7889. Altitude 110 m. Colombia. (Appendix 3.1) Forests of Caraipa longipedicellata and Micrandra sprucei Cover area: 69,917.91 km2 (Figs. 3.5 and 3.6)	The forests of Caraipa longipedicellata and Micrandra sprucei exhibit medium statures and densities. These are composed of trees with a DBH average greater than 10 cm. In some areas there are some emergent trees of up to 35 m. The highest heights were recorded to Parahancornia negroensis (35 m), P. surrogata (28 m), Discophora guianensis (26.5 m), Caraipa llanorum (21.5 m), and Micrandra sprucei (20 m). Some of the species that present a high physiognomic expression in this syntaxon are: Micrandra sprucei (18.7%), Aspidosperma verruculosum (8.9%), Henriquezia nitida (6.6%), Caraipa longipedicellata (5.4%), Parahancornia surrogata (3.2%), Pradosia schomburgkiana (1.8%), Chrysophyllum amazonicum (1.8%), and Doliocarpus novogranatensis (1.5%).	This association is defined on the basis of 17 samples that included 222 species, 145 genera and 60 families. This syntaxon is named with the elective species Caraipa longipedicellata and the dominant species Micrandra sprucei; Humiria crassifolia and Cyrilla racemiflora were recorded as exclusive species. Micrandra sprucei, Compsoneura debilis, and Caraipa longipedicellata are among the elective species	This association includes caatingas on white sands, “terra firme” forests, and seasonally flooded forests in black water with or without palms dominance over poorly drained sandy soils. A substrate that tolerate considerable differences in drainage classes, probably by the root mat develops in the litter layer. The forest of the association Caraipo longipedicellatae Micrandretum spruceii was described based on 17 samples located in Colombia (e.g., Atabapo and Guasacavi rivers, near of Inirida, Mirití, Mitú towns, and the “Serranía de Naquén”) and Venezuela (e.g., along San Carlos de Río Negro-Solano road). Detailed information about these localities is found in Appendix 3.2.
2. Oenocarpodo batauae - Eperuion leucanthae all. Nov. (Figs. 3.5 and 3.6) Typus: Micrandro elatae - Micrandretum spruceii (this study; Appendix 3.1) Lowlands forests of the Oenocarpus bataua and Eperua leucantha Cover area: 38,073.06 km2 (Figs. 3.5 and 3.6)	The forest communities of this alliance are forests of medium to high stature, reaching to 40 m height. These are characterized by the presence of trees of Apocynaceae, Arecaceae, Lauraceae, Fabaceae, Malvaceae, Moraceae, and Myristicaceae.	This alliance is defined on the basis of 61 samples that included 852 species, 323 genera in 87 families. Oenocarpus bataua (as the elective species) and Eperua leucantha (as the dominant) were chosen to coined the name of this syntaxon. The exclusive species are: Erisma micranthum, Retiniphyllum concolor, and Hevea rigidifolia. Eperua leucantha, Clathrotropis glaucophylla, Macrolobium limbatum, and Micrandra sprucei were registered as elective species. This alliance comprises two new upper Rio Negro typical associations such as the Amazonian caatinga, and the “Yévaro” forests (Micrandrum elatum - Micrandrum spruceae and Oenocarpodo batauae Eperuetum purpureae).	This alliance contains low and high Caatingas on white sands, “terra firme” forests and seasonally flooded forests in black water with or without palms dominance. The Oenocarpus bataua—Eperua leucantha alliance is located on elevated positions in depressions, very poorly drained sandy Spodosols on plains, with similar characteristics to the Spodosols located in the San Carlos de Rio Negro (Herrera 1979, 1985; Schargel and Marvez 2009).
2.1. Micrandro elatae - Micrandretum spruceii assoc. nov. (Figs. 3.5 and 3.6) Typus: Plot CC_154, TWINSPAN ID 93. Coordinates datum WGS84 LAT 3.0833, LON -67.7833. Altitude 108 m. Colombia. (Appendix 1) Forests of Micrandra elata and Micrandra sprucei Cover area: 21,835.99 km2 (Figs. 3.5 and 3.6)	The forests of Micrandra elata and M. sprucei are of medium stature (28 and 25 m) and high density composed of trees with a DBH greater than 10 cm. Calophyllum brasiliense (30 m), Hevea benthamiana (30 m), H. guianensis (30 m), and Sloanea floribunda (30 m) recorded the highest heights in this formation. The species with the biggest dominance expression (relativized units) are: Micrandra sprucei (25.4%), M. elata (6.9%), Caraipa longipedicellata (4.1%), Hevea benthamiana (3.1%), Eperua leucantha (3.0%), E. obtusata (2.8%), Hevea pauciflora (2.7%), Micrandra sprucei (2.7%), and Macrolobium limbatum (2.1%).	This association is defined on the basis of 18 samples that included 255 species, 136 genera in 52 families. This syntaxon was named used Micrandra elata (the elective species) and Micrandra sprucei as the dominant. Chrysophyllum bombycinum and Hevea benthamiana were recorded as exclusive species. Among the elective species are: Micrandra sprucei, M. elata, Macrolobium limbatum, Ficus guianensis, Caraipa longipedicellata, and Mucoa duckei.	This kind of vegetation is composed of low and high caatingas on white sands, “terra firme” forests and seasonally flooded forests over black and white water with or without palms dominance. The forest of the association Micrandrum elatum-Micrandrum spruceanum can be found on areas in upper Rio Negro over poorly drained sandy soils. This community tolerates considerable differences in drainage classes. This association was determined based on 18 samples located in Colombia (e.g., near Inírida, Almidón/La Ceiba area, Chorro Bocón at Inírida river, Campo Alegre at Cuiarí river) and Venezuela (e.g., La Esmeralda, upper Orinoco river, along Maroa-Yavita road). Detailed information on these localities is found in Appendix 3.2.
2.2. Oenocarpodo batauae - Eperuetum purpureae assoc. nov. (Figs. 3.5 and 3.6) Typus: Plot CC_115, TWINSPAN ID 54. Coordinates datum WGS84 LAT 3.3822, LON -67.3386. Altitude 101 m. Colombia. (Appendix 3.1) Forests of Oenocarpus bataua and Eperua purpurea Cover area: 16,237.07 km2 (Figs. 3.5 and 3.6)	The forests of Oenocarpus bataua and Eperua purpurea are medium to tall stature and high density. These are composed of trees with a DBH average diameter greater than 10 cm. The canopy of the forest is composed of trees of between 20 and 40 m with a dense cover and great number of palms. In this association, the following species registered the highest heights: Eperua purpurea (46 m), Erisma japura (40 m), Eschweilera tessmannii (40 m), Monopteryx uaucu (40 m), Pseudoxandra leiophylla (37 m), Vochysia grandis (37 m), and Oenocarpus bataua (25 m). The species with the most physiognomic expression are Eperua purpurea (10.3%), Micrandra sprucei (6.3%), Swartzia parvifolia (4.4%), Eperua leucantha (3.6%), Leopoldinia piassaba (3.2%), Monopteryx uaucu (3.1%), Erisma japura (3.0%), Oenocarpus bataua (2.4%), and Aldina kunhardtiana (2.0%).	This association is defined on the basis of 44 samples that included 761 species, 297 genera in 82 families. The elective species Oenocarpus bataua and the dominant species Eperua purpurea, were chosen to coined the name of this syntaxon. Within the elective species are: Brosimum utile, Minquartia guianensis, Virola elongata, Pseudolmedia laevigata, Clathrotropis glaucophylla, Iryanthera crassifolia, Erisma splendens, Ocotea aciphylla, Roucheria Columbiana, and Leopoldinia piassaba.	This association harbors the low and high caatingas on white sands, “terra firme” forests and seasonally flooded forests over mixed water with palms dominance. The forest of the association Oenocarpodo batauae Eperuetum purpureae can be found on areas in the upper Rio Negro over poorly drained sandy soils. This type of vegetation was described based on samples located in Colombia (e.g., along Atabapo river, Nabuquén at Inírida river, upper Isana river) and Venezuela (Casiquiare channel, near San Carlos de Río Negro). Detailed information on these localities is found in Appendices 3.2, 3.3 and 3.4.
3. Monopterygo uaucus - Eperuion purpureae all. Nov. (Figs. 3.5 and 3.6) Typus: Aldino heterophyllae Eperuetum leucanthae (this study; Appendix 3.1) Lowlands forests of Monopteryx uaucu and Eperua purpurea Cover area: 120,675.10 km2 (Figs. 3.5 and 3.6)	The communities of this alliance are composed of forests of medium to high stature (up to 30–45 m tall), characterized by the presence of emergent trees. According to the abundance, frequency and basal area values, the most important families are Apocynaceae, Arecaceae, Lauraceae, Fabaceae, Malvaceae, Moraceae, and Myristicaceae.	This alliance is defined on the basis of 27 samples, that included 919 species, corresponding to 314 genera in 78 families. Monopteryx uaucu as the elective species, and Eperua purpurea as the dominant were chosen to coined the name of this syntaxon. Within the elective species are: Eperua leucantha, Hevea guianensis, Micrandra sprucei, M. spruceana, Brosimum guianense, Erisma japura, Eschweilera pedicellata, Monopteryx uaucu, Iryanthera laevis, Zygia claviflora, Micropholis guyanensis, and Abarema jupunba. Other species can be shown in Appendix 3.1.	This kind of vegetation assembles low and high Caatingas on white sands and “terra firme” forests. The Monopteryx uaucu—Eperua purpurea alliance hold forests with four vertical layers. This forest was located on a poorly drained sandy Entisol in depression, on a moderately drained Ultisol on a hill, and a poorly drained Inceptisol on a foot-slope of a low hill. Both the Ultisol and the Inceptisol have sandy loam, and sandy clay loam textures below the sandy surface horizon (Schargel and Marvez 2009).
3.1. Aldino heterophyllae Eperuetum leucanthae assoc. nov. (Figs. 3.5 and 3.6) Typus: Plot S_6, TWINSPAN ID 218. Coordinates datum WGS84 LAT −0.1007, LON -66.8804. Brazil. (Appendix 3.1) Forests of Aldina heterophylla and Eperua leucantha Cover area: 9358.28 km2 (Figs. 3.5 and 3.6)	The forests of Aldina heterophylla and Eperua leucantha are of medium stature and high density. These are composed of trees with a DBH average greater than 10 cm. In some areas there are some emergent trees of up to 46 m; the highest heights were recorded to Scleronema micranthum (46.4 m), Brosimum utile (35 m), Erisma laurifolium (35 m), protium alvarezianum (35 m), Swartzia tomentifera (34.4 m), Eperua purpurea (30 m), E. leucantha (30 m), and Aldina heterophylla (28.1 m). Several species presented higher physiognomic expression in this syntaxon (relativized units) such as: Eperua leucantha (13.1%), E. purpurea (9.4%), Monopteryx uaucu (7.3%), Aldina heterophylla (4.7%), Clathrotropis macrocarpa (3.6%), Micrandra spruceana (3.0%), Scleronema micranthum (2.2%), Swartzia polyphylla (1.6%), and Swartzia tomentifera (1.3%).	This association is defined on the basis of 19 samples that included 716 species, 262 genera in 70 families. This syntaxon is named used Aldina heterophylla (the exclusive species) and Eperua leucantha (the dominant species). In this vegetation pattern, Chamaecrista adiantifolia, Sloanea obtusifolia, Himatanthus obovatus, Pradosia schomburkiana, and Vitex sprucei were identified as exclusive species. Within the elective species are: Swartzia tomentifera, Trattinnickia glaziovii, Ocotea rhynchophylla, Sandwithia guyanensis, Brosimum rubescens, Pouteria cuspidata, Bocageopsis pleiosperma, Virola calophylla, Erisma calcaratum, Micrandra spruceana, Hevea guianensis, Chimarrhis duckeana, Couma guianensis, and Cyrillopsis paraensis.	This kind of vegetation harbors low caatingas on white sands and “terra firme” forests. The forest of the association Aldino heterophyllae - Eperuetum leucanthae can be found on areas in the upper Rio Negro growing on poorly drained sandy soils; it tolerates considerable differences in drainage class. This association was determined based on 19 samples located in Brazil (e.g., São Gabriel da Cachoeira, middle Içana river, Pico da Neblina National Park), Colombia (e.g., Punta de Tigre, upper Isana river) and Venezuela (i.g. Mawarinuma river at the base of “Sierra de la Neblina”) as well. Detailed information on these localities is found in Appendix 3.2.
3.2. Eperuo purpureae - Erismetum japurae assoc. nov. (Figs. 3.5 and 3.6) Typus: Plot P6, TWINSPAN ID 191. Coordinates datum WGS84 LAT 2.2071, LON -68.2781. Colombia. (Appendix 3.1) Forests of Eperua purpurea and Erisma japura Cover area: 111.316.82 km2 (Figs. 3.5 and 3.6)	The forests of Eperua purpurea and Erisma japura have a medium to tall stature, high density and great number of palms. The trees have a DBH average greater than 10 cm. In this association the following species have the highest heights: Pouteria ucuqui (45 m), Eschweilera collina (44 m), Brosimum utile (40 m), Micropholis brochidodroma (40 m), Swartzia floribunda (40 m), Allantoma lineata (35 m), Ecclinusa ramiflora (35 m), and Goupia glabra (35 m). The species with most physiognomic expression (relativized units) are: Erisma japura (18.3%), Eperua purpurea (13.9%), Goupia glabra (3.3%), Heterostemon conjugatus (2.9%), Ecclinusa ramiflora (2.9%), Swartzia pinnata (2.5%), Sandwithia heterocalyx (2.5%), Pseudosenefeldera inclinata (2.1%), Hevea guianensis (2.1%), and Eschweilera pedicellata (2.0%).	This association is defined on the basis of 8 samples, that included 332 species, 169 genera in 55 families. Eperua purpurea (as elective species) and Erisma japura (as the dominant) were chosen to name this taxon. Within the elective species are: Protium crassipetalum, Aldina kunhardtiana, Heterostemon conjugatus, Swartzia pinnata, Clathrotropis glaucophylla, Oenocarpus bacaba, Ecclinusa bullata, Helianthostylis steyermarkii, and Pouteria guianensis. Other species can be shown in the Appendix 3.1.	This association assembles the “terra firme” forests and the tall caatingas. The forest of the association Eperuo purpureae Erismetum japurae can be found on areas in the upper Rio Negro growing on poorly drained sandy and clay soils; it tolerates considerable differences in drainage classes. This kind of vegetation was described based on eight (8) samples located in Colombia (e.g., mouth of Naquén river, Puerto Colombia - Guainía) and Venezuela (e.g., Maroa-Yavita road). Detailed information on these localities is found in Appendix 3.2.
ORDER II 1. Goupio glabrae - Minquartiion guianensis all. Nov. (Figs. 3.5 and 3.6) Typus: Eschweilero parviflorae - Mouririetum grandiflorae (this study; Appendix 1) Lowlands forests of the Eschweilera parviflora and Mouriri grandiflora Cover area: 333,950.47 km2 (Figs. 3.5 and 3.6)	The forest communities of this alliance are medium to high in stature, up to 45 m tall. These communities are characterized by the presence of trees of Arecaceae, Burseraceae, Lauraceae, Lecythidaceae, Fabaceae, Melastomataceae, Moraceae, Myristicaceae, Olacaceae, Rubiaceae, Sapindaceae, and Sapotaceae.	This alliance is defined on the basis of 95 samples that included 1983 species, 532 genera in 120 families. This syntaxon is named with the exclusive species Goupia glabra and the dominant species Minquartia guianensis. In this vegetation alliance others exclusive species were: Abuta grandifolia, Cynometra marginata, Mabea nitida, Clarisia racemosa, Oenocarpus minor, and Richeria grandis. The elective species are: Dendrobangia boliviana, Siparuna guianensis, Mouriri grandiflora, Virola elongata, Heterostemon mimosoides, Trichilia micrantha, and Xylopia nervosa. This alliance includes two associations: An undefined named compound by Attalea Maripa and Brosimum utile, and the Eschweilero parviflorae - Mouririetum grandiflorae.	This alliance is compound by “terra firme” forests, forests with palm dominance and seasonally flooded forests in white and clear waters with or without palm dominance. The Eschweilea parviflora—Mouriri grandiflora order is located on in the transition between alluvial plains and the hills (“lomeríos”) over Ultisol and poorly drained Entisol.
1.1 Attalea Maripa - Brosimum utile (Figs. 3.5 and 3.6). Representative plot no. P2, TWINSPAN ID 187. Coordinates datum WGS84 LAT 1.7449, LON -69.7660. Altitude 193 m. Colombia, Venezuela and Brazil (Appendix 3.1) Forests of Attalea Maripa and Brosimum utile Cover area: 267,160.37 km2 (Figs. 3.5 and 3.6)	The forests of Attalea Maripa and Mespilodaphe cymbarum are communities of medium to high stature and density, mainly composed by trees with a DBH average greater than 15 cm. This analysis was outline such as an undefined association. The canopy of the forest is composed of trees with heights between 20 and 40 m. Brosimum utile, Euterpe precatoria, Matayba elegans, Eschweilera parviflora, and Virola elongata being the most abundant species. Some of the highest heights were recorded in Minquartia guianensis (58 m), Aldina latifolia (40 m), Brosimum utile (40 m), Caryocar glabrum (40 m), Eschweilera parviflora (40 m), Mespilodaphe cymbarum (40 m), Vochysia assua (40 m), V. grandis (40 m), and Attalea Maripa (20 m).To this syntaxon the species with the biggest dominance expression are Eschweilera parviflora (3.0%), Attalea Maripa (1.9%), Goupia glabra (1.7%), Allantoma lineata (1.6%), Swartzia tomentifera (1.5%), Euterpe precatoria (1.4%), Minquartia guianensis (1.3%), Chaetocarpus schomburgkianus (1.3%), and Brosimum utile (1.2%).	This kind of vegetation was defined on the basis of 68 samples, that included 1905 species, 516 genera in 117 families. This group of undefined associations registered Attalea Maripa as the elective species, and Brosimum utile as the dominant. As exclusive species were registered: Brosimum utile, Zygia cataractae, Maprounea guianensis, Mouriri acutiflora, Garcinia madruno, Piper arboreum, protium laxiflorum, Zygia inaequalis, and Homalolepis cedron. Other exclusive species can be shown in the Appendix 3.1. Among the elective species are: Gustavia augusta, Myrcia fallax, protium stevensonii, Inga acrocephala, Macrosamanea amplissima, Maquira calophylla, Duguetia quitarensis, and Gustavia acuminata. Other species can be shown in Appendix 1.	This vegetation is represented by “terra firme” forests, flooded forests with palm dominance, and seasonally flooded forests with or without palm dominance. The forest of Attalea Maripa and Brosimum utile assembles 68 samples located in Brazil (e.g., near Manaus city, Uatuma river, Pico da Neblina National Park), Colombia (i.g. Cumaribo-Vichada, Mitú, middle Caquetá river, “El Retiro” (“La Lindosa”), Inírida river, near mouth of “caño Bocón,” Guaviare river, upper Isana river) and Venezuela (e.g., along Casiquiare river, middle and lower Ventuari river). Detailed information on these localities is found in Appendix 3.2.
1.2 Eschweilero parviflorae - Mouririetum grandiflorae assoc. nov. (Figs. 3.5 and 3.6). Typus: Plot CC_173, TWINSPAN ID 112. Coordinates datum WGS84 LAT 3.7917, LON -67.8197. Altitude 108 m. Colombia. (Appendix 3.1). Forests of Eschweilera parviflora and Erisma laurifolium Cover area: 66,790.09 km2 (Figs. 3.5 and 3.6)	The forests of Eschweilera parviflora and Erisma laurifolium are communities of medium to high stature and density, mainly composed of trees with a DBH average greater than 15 cm. Protium divaricatum, Eschweilera parviflora, Brosimum utile, Pouteria baehniana, Mouriri grandiflora, Clathrotropis brachypetala, and Virola elongata being the most abundant species. In this association following species registered the highest heights Clathrotropis glaucophylla (35 m), Eperua purpurea (35 m), Erisma laurifolium (35 m) Goupia glabra (35 m), Vochysia splendens (33 m), Caryocar glabrum (32 m), Qualea ingens (32 m), Eschweilera parviflora (30 m), and Mouriri grandiflora (30 m). Some of the species that present a high physiognomic expression in this syntaxon (relativized units) are: Eperua purpurea (5.2%), Caryocar glabrum (4.2%), Mouriri nigra (3.4%), Goupia glabra (2.9%), Leopoldinia piassaba (2.7%), Leptobalanus apetalus (2.6%), Eschweilera parviflora (2.6%), protium divaricatum (2.4%), Virola elongata (2.2%), and Mouriri grandiflora (1.8%).	This association is defined on the basis of 28 samples that included 373 species, 176 genera and 60 families. This syntaxon is named with the exclusive species Eschweilera parviflora and the dominant species Mouriri grandiflora. In this vegetation pattern Pouteria baehniana was registered as exclusive species. Within the elective species are: Clathrotropis brachypetala, Mouriri grandiflora, Eschweilera parviflora, Virola elongata, protium divaricatum, Erisma laurifolium, and Aptandra tubicina. Other species can be shown in the Appendix 1.	This association is compound by “terra firme” forests and seasonally flooded forests with or without palms dominance. The forest of the association Eschweilero parviflorae Mouririetum grandiflorae was determined based on 28 samples located in Colombia (e.g., Guaviare river at mouth Inírida river, near Inírida, Nukak reservation). Detailed information on these localities is found in Appendix 3.2.
2. Astrocaryo chambirae - Socrateion exorrhizae all. Nov. (Figs. 3.5 and 3.6). Representative plot. GB_8, TWINSPAN ID 172. Coordinates datum WGS84 LAT 2.4232, LON -72.3699. Colombia. (Appendix 3.1) Lowlands forests of the Astrocaryum chambira and Socratea exorrhiza without indefinite associations Cover area: 6958.74 km2 (Figs. 3.5 and 3.6)	The forest communities of this alliance are medium to high stature, up to 25–30 m tall, characterized by the high presence of palms and trees of Burseraceae, Lauraceae, Lecythidaceae, Fabaceae, Melastomataceae, Moraceae, Myristicaceae, Rubiaceae, Sapindaceae, and Sapotaceae. Some of the highest heights were recorded in Vochysia splendens (26.5 m), Virola marleneae (22.4 m), Clathrotropis macrocarpa (21.4 m), Socratea exorrhiza (13.9 m), and Astrocaryum chambira (9.3 m). The species with most physiognomic expression are Erythroxylum macrophyllum (6.8%), Psychotria remota (6.0%), Palicourea raveniana (6.0%), Sorocea muriculata (4.8%), Theobroma subincanum (2.5%), Socratea exorrhiza (2.3%), Astrocaryum chambira (2.1%), Miconia punctata (2.0%), Pseudolmedia laevis (1.8%), and Clathrotropis macrocarpa (1.8%).	This alliance is defined on the basis of 16 samples that included 102 species, 79 genera and 39 families. Astrocaryum chambira (as the elective species) and Socratea exorrhiza (as the dominant) were chosen to name this syntaxon. As exclusive species were registered: Inga tessmannii, Psychotria remota and Jacaratia spinosa. The elective species are: Calycophyllum megistocaulum, Astrocaryum chambira, Pseudolmedia laevis, Euterpe precatoria, and Socratea exorrhiza.	This alliance is composed of “terra firme” forests with palms dominance, located in the transitions between the alluvial plains and the terraces over Entisol and Ultisol soils. This kind of vegetation was described based on 16 samples located in Colombia (e.g., San José del Guaviare. Nabuquén creek, Puinawai natural reserve). Detailed information on these localities is found in Appendix 3.2.

Appendix 3.2 Botanical Explorations in the Rio Negro Basin: A Review

1.1 Introduction

The record of human occupation in the upper Rio Negro basin, based on ceramic shards, dates back to between 3750 (Sanford et al. 1985) and 3570 (Neves 1998) years B.P. Other data, based on soil charcoal samples, dates human occupation to between 640 and 250 years B.P. for the top 20 cm soil layers, and between 6260 and 530 years B.P for the lower 20–90 cm soil layers (Saldarriaga and West 1986). It is interesting that the dates reported by these authors correspond with dry episodes in the Amazon basin and surrounding areas (van der Hammen 1972; Bush and McMichael 2016). The authors suggest that dry and humid periods alternated from 6000 to 400 B.P. The age estimated from charcoal and shards confirms that the region has been subjected to fires during extreme dry periods, and indicates periods of human disturbance (e.g., shifting cultivation) for the last 3750 years.

It is well known that the region comprising the upper Río Negro and Orinoco basins was traveled, explored, and inhabited for several millennia by ancestral groups such as the Makú-Puinave, the Arawak, and the Tucano (Zucchi 2006). Migrations or movements of these ancestral groups came from the Central Amazon region to the Rio Negro basin approximately 4500–3500 B.P. (Meggers 1979), perhaps escaping the devastating droughts or Mega-Niño events that took place in Central Amazonia during this time (Meggers 1994; van der Hammen 2006; Olivares et al. 2015). No doubt, the Río Negro basin was relatively well explored by the earliest inhabitants of the region, who were able to classify vegetation types and its most important plant species before Europeans arrived (Abraão et al. 2009). Also, Pre-Columbian populations categorized Amazonian rivers by the color of their water, and they knew that water color was related with fish richness or soil fertility (Junk et al. 2011).

1.2 The Journeys

1.2.1 Fifteenth to Nineteenth Centuries

The first Iberian journeys down the Amazon river, from the Andes to the Atlantic Ocean, were undertaken by two groups of Spaniards, one commanded by Francisco de Orellana (1541–1542) and later by Pedro de Ursúa (1560–1561) accompanied by, among others, the infamous Lope de Aguirre. Chronicles of these travels, written by Fray G. de Carvajal in the case of Orellana’s saga (Carvajal 1848), and by several witnesses and second-hand accounts in the case of Ursúa and Aguirre’s (e.g., Vazquez 1881), spoke of large areas of forest along the Amazon river and numerous, well-populated native villages. During Orellana’s journey a mighty black water river was sighted flowing from “El Poniente,” and was called “Río Negro” (Carvajal 1848).

After the two Iberian voyages down the Amazon river, the interest in knowing the Amazon basin in greater detail took a remarkable impact at the cartographic level, especially by the French, Portuguese, and Jesuits and Franciscans priests (Cintra 2012a). The first accurate map of the Amazon River was drawn by French cartographers, including one by Count of Blaise François Pagan (1655) and several by Nicolas Sanson (1656, 1657, 1680, 1698, and 1699), drawn and engraved during the golden age of French cartography (Cortesão 1965). Pagan’s map, Magni Amazoni Fluvii (Pagan 1655), is considered the most remarkable of all the charts, not just of the Amazonas river, but of the whole of Amazon basin (Cortesão 1965; Cintra 2011). It was based mainly on the account of Father Cristóbal de Acuña, who descended the river with Pedro Teixeira in 1639, and determined some latitudes and estimated distance in leagues between consecutive locations. This chart was the first established canvas of the meridians and parallels that scientifically situated the Amazon and took full advantage of the geographic data supplied by the discoverers. Nicolas Sanson (the royal cartographer of France) published his first Amazonas map in 1656. He improved his first map with several versions published in 1657, 1680, 1698, and 1699. The maps of the Amazon River traced by Sanson present precise geographic coordinates considering its time, shows a well-determined prime meridian, and also employs a creative methodology to deduce longitudes from latitudes and distances that had been covered (Cintra and de Oliveira 2014). After Pagan’s and Sanson’s maps, the Jesuit priest Samuel Fritz drew a map of the Amazon in 1691 and later had one engraved in 1707. Much simplified versions of Fritz’ map were first published in 1717 (engraved in French), 1726 (in German), 1755 (in Spanish), and in 1819 (a second version in French), accompanying an extract of his description of the “Maragnon.” Of the map engraved in 1707, apparently, only a few copies circulated are fewer are extant; the other four maps were published in “Lettres Édifiantes et Curieuses” (in Fritz 1717 and 1819, for the first and second versions in French, respectively), in Der Neüer Welt-Bott (Fritz 1726, in German), and “Cartas edificantes, y Curiosas” (Fritz 1755), journals then little read outside religious circles. It is evident that the scientific cartography of Amazonas begins with the map of Count of Pagan (for a review see: Cintra 2011, 2012b; Cintra and Freitas 2011; Cintra and Furtado 2011; Cintra and de Oliveira 2014).

Some years later, researchers started collecting plants and studying the vegetation of the Amazon river. Charles de La Condamine, who navigated this river in 1743, wrote the first biological report (de La Condamine 1745). European scientists considered his expedition the beginning of the great era of Amazonian travel (ter Steege et al. 2016). La Condamine remarked on numerous plant products such as curare, the arrow poison, derived from Strychnos spp. (Loganiaceae); he also documented for the first time the quinine tree, Cinchona officinalis L. (Rubiaceae) and the rubber tree, Hevea spp. (Euphorbiaceae). However, the first known large collection of Amazon plants was made by Alexandre Rodrigues Ferreira (1756–1815) during his voyage of 1783–1792 (Wurdack 1971). He explored the Amazon river and its main tributaries, including the Rio Negro and Rio Branco between 1785 and 1786, where his itinerary notably included the Isana and Vaupés rivers (Pereira da Silva 2008). His group collected and drew numerous plants and animals during this expedition. Asteranthos brasiliensis Desf. (Scytopetalaceae), with showy yellow, fused petals, and an actinomorphic androecium, is an endemic genus of the Rio Negro basin, and perhaps one of the most extraordinary plants they documented (see Fig. 3.12 on the text of Chap. 3).

Fig. 3.12

Asteranthos brasiliensis Desf. Lecythidaceae. Predominantly occupies a geographical range from Eastern Colombia and stretches to incorporate Southern Venezuela and Northern Brazil, with a specific concentration in the Upper Río Negro region. This species is classified as arboreal and grows best primarily in hydric or moisture-rich environments—image captured by H. ter Steege

Later, “caño” Pimichín and the rivers Guianía and upper reaches of the Río Negro were explored by the famous naturalists F. H. A. von Humboldt and A. J. A. Bonpland (in April 1800), gathering the first biological collections of that section of the Río Negro basin. They were followed by C. F. P. von Martius and J. B. von Spix (1819–1820), A. Plée (1821), L. Reidel (1828), J. B. Natterer (1830–1832), R. H. Schomburgk (1839; 1855), P. J. Ayres (1842–1844), A. R. Wallace (1850–1851), and R. Spruce (1850–1854), at a time when scientists in Europe were fascinated by the tremendous diversity of fishes, insects, mammals and plants being discovered, and before modern scientific research on ecology and evolutionary biology.

Richard Spruce (1817–1893) was remarkable among all personalities above mentioned. He was a pioneer botanical explorer of the north-west Amazon and the northern Andes in the middle of the last century. He collected ca 7000 botanical specimens and made numerous important botanical discoveries. This British botanist, who opened up the Rio Negro region to science between 1850 and 1854, must be counted amongst the greatest naturalists ever to have engaged in collecting and studies anywhere in unexplored Neotropical territories (Schultes 1983). As a result of his meticulous observation and insatiable curiosity, a basis for our understanding of great areas of the Amazon was early and most firmly laid. Not only did Spruce advance taxonomy and floristics, but he was also a notable bryologist and made many important observations in ethnology, ethnobotany, linguistics, and geology (Spruce 1908).

1.2.2 Nineteenth to twentieth Centuries

The Portuguese and later Brazilians started an ambitious plan of exploration in the Rio Negro during the nineteenth century, shortly after the consolidation of Amazonas province in 1850. Several explorers visited the watersheds of main affluents (for a review see: Tenreiro-Aranha 1906). After this period, the exploration of the Rio Negro basin and its most important rivers continued with the work of, among others, G. Wallis (1863–1864), J. W. H. Traill (1874), J. Barbosa Rodrigues (1884–1885), P. H. W. Taubert (1896), E. H. G. Ule (1901–1902), É. Bommechaux (1903), G. A. E. Hübner (1903–1907, 1914), C. T. Koch-Grünberg (1903–1905), J. Huber (1904), H. Schmidt and L. Weiss (1907–1908), W. A. Ducke (1910–1932, 1933–1936, 1941–1942), J. G. Kuhlmann (1918), and D. E. Melin (1924). Also, it is important to point out that large sections of the Rio Negro and some of its tributaries, as well as the Casiquiare and the upper Orinoco, were extensively explored in the first quarter of the twentieth century by H. A. Rice and P. P. von Bauer. Their emphasis was geographical exploration; unfortunately, little biological material was collected, but important cartographical material resulted from their travels (Rice 1910, 1914, 1918, 1921, 1928; von Bauer 1919).

To this list of explorers, we should also mention the many plant collectors who worked on behalf of commercial horticultural houses in Europe and the United States who, although remaining largely anonymous, were behind the discovery and introduction of many plant species, particularly orchids, bromeliads, and other ornamental plants.

After the Treaty of Bogotá between Colombia and Brazil was signed in 1907, the Brazilian government started another program of exploration in the Rio Negro basin in 1927–1929, under the charge of Marshall Boaberges Lopes de Sousa. The botanist on this expedition, F. von Luetzelburg made significant botanical collections and annotations of types of vegetation of the upper Rio Negro (Lopes de Sousa 1955, 1959); he also visited the Casiquiare channel (Huber and Wurdack 1984). Attalea luetzelburgii (Burret) Wess. Boer (Arecaceae), a palm with subterranean stems represents a notable species among the numerous plants collected during his expedition.

The exploration of the Río Negro basin continued with the field work of G. H. H. Tate (1928–1929), E. G. Holt, W. Gehriger and E. R. Blake (1930–1931), B. A. Krukoff (1936), J. Cuatrecasas (1939), R. de Lemos Fróes (1941–1952), Ll. Williams (1942), J. A. Steyermark (1944; 1970), P. H. Allen (1943–1945), F. Cardona-Puig (1946), R. E. Schultes and F. López (1947–1948), J. Murça Pires (1947–1952), G. A. Black (1947–1950), B. Maguire et al. (1950–1966), J. J. Wurdack et al. (1951–1959), H. García-Barriga (1951), R. Romero-Castañeda (1952), A. Fernández-Pérez (1953), W. A. Rodrigues (1954–1968), V. Vareschi and K. Mägdefrau (1958–1962), L. A. Garay (1960), G. Eiten (1963), J. Ewel (1964), N. T. da Silva and U. Brazâo (1966), E. Medina (1968), L. Ruiz-Terán and J. Bautista (1968), M. Fariñas et al. (1969), J. A. Steyermark, C. Brewer-Carias and G. C. K. Dunsterville (1970), P. Maas (1971), B. Manara (1971), and G. T. Prance (1971). As shown here, numerous botanists, anthropologists, and ecologists have visited the Rio Negro basin to study the flora, vegetation, ethnography, and inhabitants in the last two hundred years. In the last five decades, fieldwork was carried out primarily by botanists, ecologists, and naturalists from the three countries that share the Rio Negro basin. Multiple studies have been done, too numerous to cited them all here.

Besides this remarkable amount of fieldwork, thousands of plant collections from Amazonia (including some from the Rio Negro) were products of the 8 expeditions to the Amazon basin conducted by B. A. Krukoff in 1923–1950 (Landrum 1986), and the 25 expeditions sponsored by the bi-national plant collecting program “Projeto Flora Amazônica” (Prance et al. 1984).

In addition, thousands of botanical specimens were collected in Brazil during the execution of the “Biological Dynamics of Forest Fragments Project (BDFFP)” set up near Manaus, and resulting from the field work conducted by “Instituto Amazónico de Investigaciones Científicas SINCHI” for nearly three decades in the Colombian Amazon. Likewise, in Venezuela, many botanical collections and publications resulted from: the interdisciplinary and multi-national project conducted by the “Instituto Nacional de Investigaciones Científicas (IVIC),” perhaps the most detailed study of Amazon caatinga and terra-firme forests ever conducted in the Upper Rio Negro (Medina 2000); the “Proyecto inventario de los recursos naturales de la región Guayana-PIRNRG-” (Zinck 1986); and the expeditions to “Serranía de la Neblina” (Brewer-Carías 1988). Finally, we must cite the collections generated by “Proyecto inventario de los recursos naturales de la región Guayana-PIRNRG-”, conducted by “CVG-Tecmin” (Corporación Venezolana de Guayana-Técnica Minera, C.A.) and other national and international institutions, a major effort to inventory the natural resources of the Venezuelan Guayana. As part of this project, a multidisciplinary team studied the upper Rio Negro and Orinoco basins in 1990–1992, which gathered large sets of plant specimens, ecological data (Aymard 2001), as well as soils and rocks samples. This field work resulted in the discovery of numerous new plant species and the gathering of data for a chorological report for this region (Aymard, in preparation).