Middle Madeira River Research Articles

Diversity and similarity in parasitic infracommunities of Mylossoma aureum and Mylossoma duriventre (Characiformes, Serrasalmidae) from the Middle Madeira River Basin, Southern Amazonas, Brazil

A total of 30 specimens of Mylossoma aureum and 30 of Mylossoma duriventre from the Middle Madeira River Basin were examined between October 2020 to March 2021. Eight species of parasites were identified. About 65% of the hosts were parasitized. A total of 386 parasites was collected in M. aureum and 436 in M. duriventre. Species accumulation curves in M. aureum did not reach the asymptote, while in M. duriventre the curves showed tendency to stabilization. Contracaecum sp. larvae was the only endoparasite found. Anacanthorus paraspathulatus was the dominant species in M. aureum. In M. duriventre, the core species with highest parasite indexes was Mymarothecium sp. 3. Margalef’s and Shannon’s diversity indexes were higher in M. aureum. Most of the parasites showed an aggregated distribution pattern. Mymarothecium sp. 1, Mymarothecium sp. 2 and the parasite richness showed a significant positive correlation between its abundance and host length and between Mymarothecium sp. 1 abundance and host weight in M. aureum. All parasites are the first records for the Southern Amazonas. Except A. paraspathulatus, all M. aureum parasites are mentioned for the first time in this host. The three morphotypes of Mymarothecium spp. are probably new species that are in the process of taxonomic description.

Two new miniature translucent catfish species of the rare genus Tridens (Siluriformes: Trichomycteridae) from the Madeira River basin, northern Brazil.

Two new miniature species of the trichomycterid genus Tridens are described from the Madeira River drainage, Acre and Rondônia States, Brazil. Until this work, Tridens was a monotypic genus composed solely of Tridens melanops, from the Putumayo/Içá River drainage, upper Amazonas River basin. Tridens vitreus sp.n. is known from upper and middle Madeira River drainage and differs from all other congeners by the lack of pelvic fins and girdle and by vertebra and dorsal-fin ray counts. Tridens chicomendesi sp.n. is known from Abunã River, middle Madeira River drainage and is distinguished from all other congeners by the number of vertebrae, dorsal-fin ray count and anal-fin base colouration pattern. Tr. chicomendesi sp.n. is further distinguished from T. vitreus by a combination of character states regarding the position of urogenital opening, dorsal-fin position, anal-fin position, maxillary barbel length, number of premaxillary teeth, number of dorsal-fin rays, number of anal-fin rays, number of lateral-line system pores, frontal bone anatomy, degree of ossification of maxilla, anatomy of quadrate-hyomandibular joint, size of posterodorsal process of hyomandibula, length of opercular patch of odontodes, number of interopercular odontodes, proportion of upper hypural plate cartilage relative to its area ; by the absence of a proximal, distal and ventral cartilages on ventral hypohyal; by the absence of a lateral process on basibranchial 4; by the presence of a cartilage block on the lateral process of autopalatine, the presence of a well-developed ossification on proximal margin of ventral hypohyal, the presence of hypobranchial foramen; and by the presence of an anterior cartilaginous joint between quadrate and base of posterodorsal process of hyomandibula. This work represents the first species description for the subfamily Tridentinae in more than 30 years and for the genus Tridens since its original description in 1889.

Identificación de potenciales zonas de desove del dorado (Brachyplatystoma rousseauxii) en la cuenca Madeira

Gilded catfish (dorado) Brachyplatystoma rousseauxii is one of the most threatened Amazon fish species. Its complex life cycle is interrupted by hydroelectric dams that were built on the middle Madeira River. Despite this, the species seems to continue spawning in the Beni River, a tributary of the Madeira River. We conducted a spatial analysis that allowed us to identify aditional spawning sites in the Madeira basin. Hydrological and topographic information available at watershed level was used and a similarity analysis was performed to geographically locate potential spawning areas. Seventy sub-basins were identified that meet the same characteristics as the documented spawning area in Beni and might constitute 22 potential spawning areas for dorado. All identified zones correspond to >4th order tributaries with a direct origin in the Andes. The precise identification of these zones allows the planning of monitoring efforts using a citizen science approach to confirm the reproduction of dorado in the Madeira basin and will help generate information that may serve to prevent species extinction in this basin.

Database of the historical series of fisheries production in the middle Madeira River region, southwest of the Amazon, from 2001 to 2013

The Amazon is very important regarding the continental extractive fishing as it has the greatest diversity of freshwater fish in the world. Some factors can contribute to identify significant changes in fish production, such as characterization based on common names, and synonyms or classifications only at the genus level. This creates noise in different types of analyzes and mistakes in determining effective productions, as well as levels of exploitation for management. Thus, this study aims to demonstrate the variation in fish production over the years 2001 and 2013, using control data from the fishing colony "Dr. Renato Pereira Gonçalves Z-31" in the municipality of Humaitá, southern Amazonas. These data were analyzed by collaborators from the Laboratory of Ichthyology and Fisheries Management of the Madeira River Valley, at the Federal University of Amazonas. The fish landing monitoring allowed the determination of the species caught in the regional fishery and evaluated the effect of the hydrological level and the pre- and post-installation periods of the Santo Antônio and Jirau HPPs in Rondônia, on the total production. The data set showed the significant decrease in fish production between 2008 and 2013. Among the factors that explain the observed changes are the mistakes in determining the effective production due to the lack of criteria in the grouping of many species, the absence of regulations, such as the "Portaria IBAMA Nº 48" which was created only in 2007, in addition to the installation period of the HPPs on the Madeira River. It was also possible to verify the effect of seasonality through hydrological quotas on fish production, with the highest values observed in July, August and September of the years analyzed.

The role of Late Pleistocene-Holocene tectono-sedimentary history on the origin of patches of savanna vegetation in the middle Madeira River, southwest of the Amazonian lowlands

Savanna patches are features of the Amazonian landscape that have been long under intense debate, but there are still questions about the main factors that have determined their establishment and evolution within the rainforest matrix. In particular, their geological substrates were poorly documented. The aim of this work is to reconstruct the tectono-sedimentary history of four savanna patches in the middle Madeira River, southwest Amazonia, and discuss its potential control over the development of the savanna communities. The approach consisted in the integration of geomorphological, sedimentological, chronological and floristic data. The results revealed that the savanna substrates are sandy deposits aged between 118.9 and 35.6 ky, overlain by late Pleistocene to Holocene muddier successions <25,700 cal yr BP. Most of the geologically stable and topographically higher terrains of the geomorphological unit T1 is dominated by forests. These intermingle with open habitats formed by renewed sedimentation that were colonized by tree and shrub species of the Amazonian biome. By contrast, the ground of unit T2 subsided to a level that allowed the meandering of the main river. This process resulted in the replacement of the rainforest by open habitats dominated by savannas with lower richness and diversity than in the T1 unit, which were dominated by species with wide distribution in the cerrado biome of Central Brasil. The cerrado species might have expanded into this region during Pleistocene drier climatic episodes, but environmental filters shaped by geological processes determined the floristic contrasts between units T1 and T2. The lack of competition with Amazonian species probably constituted an important factor for the preferential colonization of arboreal and shrubby species from neighboring cerrados on meandering scroll bars, marginal levees and crevasse splays of unit T2.

Upstream dam impacts on gilded catfish Brachyplatystoma rousseauxii (Siluriformes: Pimelodidae) in the Bolivian Amazon

ABSTRACT This paper explores the effects of two run-of-river dams (Jirau and Santo Antônio) built in cascade in the middle Madeira River (Brazil) on the interruption of long-distance migration routes of the gilded catfish (Brachyplatystoma rousseauxii). A participative monitoring system was set up to compare capture by commercial fishers approximately 1500 km upstream of the dams in Bolivia, before (1998-2007) and after (2015-2017) dam closure. A significant decrease in gilded catfish catches and in catch per unit effort was observed after dam closure, whereas no significant difference in mean weight was found. Back-estimation of age suggests that the few individuals remaining after dam closure in 2009 are a mixture of old homers that returned upstream before dam closure, and residents hatched after dam closure and trapped in the upper Madeira. Unless fishways in the Madeira River dams improve their efficiency, the gilded catfish might become rare and in danger of regional extinction in the upper Madeira basin in the next few years, negatively affecting river fisheries.

INDICADORES ECOSSISTí­Å MICOS DE UMA PESCA DE PEQUENA ESCALA COM DADOS LIMITADOS NO RIO MADEIRA (BRASIL)

Este trabalho apresenta uma análise baseada em indicadores para pesca de pequena escala que opera no médio rio Madeira (Brasil), afluente do rio Amazonas. Foram utilizados dados de desembarques diários da Colônia de Pescadores de Porto Velho que registrou a produção das espécies (kg) capturadas entre 1990 e 2009 e o comprimento total durante cinco anos. As espécies foram classificadas por ní­­vel trófico, e foram calculados o balanço na pesca, í­­ndice L e as classes de tamanho. Além disso, as diferenças nos desembarques totais anuais (kg) foram correlacionadas com o ní­­vel da água do rio Madeira (cm). A captura anual média foi de 566,5 toneladas (± 193,6), com variação significativa entre os anos e não correlacionadas com o ní­­vel da água do rio. Os indicadores do ecossistema mostraram uma tendência estável, com oscilações nos últimos anos, refletindo maior captura de espécies com maiores comprimentos e ní­­vel trófico. Os gestores de pesca em regiões com dados pesqueiros limitados podem considerar esses indicadores para análises de estoque de peixes como de baixo custo, práticos e fáceis de calcular.

&lt;b&gt;Jatuarana fishing dynamics &lt;i&gt;Brycon amazonicus&lt;/i&gt; (Spix &amp; Agassiz, 1829) of the upper and middle Madeira River Basin

The jatuarana ( Brycon amazonicus ), is an important species for the Madeira River commercial fisheries. The paper aims to characterize the jatuarana fishing dynamics in the middle Madeira River and test whether there are differences dowstreams and upstreams the Teotonio waterfall. Commercial fisheries landings were monitored daily at 15 ports or riverine communities along that stretch, using semi-structured interviews with fishermen. With data from the fishing monitoring program of UHEs Santo Antonio and Jirau we analysed: the yield, catch per unit effort (CPUE), length structure, locations and fishing gear used, between 2009 to 2011.The fishing yield of this species was temporaly analyzed with data from the Fishermen Colony of Porto Velho city (Rondonia state, Brazil), between 1990 to 2012. The yield and the CPUE showed significant differences by area and locations and the capture of the species was carried out primarily in the channel river and banks river through gillnets. In addition, the samples collected in the upstream area have higher distribution and modal lengths than from those collected downstream. These results suggest that the areas require distinct management measures.

The role of fertile anthropogenic soils in the conservation of native and exotic agrobiodiversity in Amazonian homegardens

Amazonian dark earths (ADE) are anthropogenic soils mostly created between 500 and 2500 years ago by pre-Columbian populations. ADE are currently used by local people for different agricultural and agroforestry systems. Because of their high fertility they may play an important role in the conservation of non-native agrobiodiversity. This study aimed to investigate the variation in richness and abundance of exotic and native species in homegardens along the ADE-background soil continuum. We conducted floristic inventories in 70 homegardens located in 7 riverside communities along the lower and middle Madeira River, Central Amazonia. Each species sampled was classified according to its origin: native Amazonian, American (from outside Amazonia) and non-American, and each individual was classified according to its form of establishment: cultivated or spontaneous. The floristic diversity was significantly related to soil fertility, texture and homegarden size. We found a positive relationship between soil fertility and richness of species and landraces. Homegardens on more fertile soils tended to have a higher richness and abundance of cultivated non-American species, as well as a higher richness and abundance of spontaneously established American species. Homegardens at the fertile end of the fertility gradient provided conditions for the establishment and growth of many species, especially exotic species, that are generally more nutrient-demanding than Amazonian species. Our results show that homegarden agroecosystems on ADE favour experimentation with the introduction of a wide range of species from various regions of the globe.

High genetic diversity among and within bitter manioc varieties cultivated in different soil types in Central Amazonia

Although manioc is well adapted to nutrient-poor Oxisols of Amazonia, ethnobotanical observations show that bitter manioc is also frequently cultivated in the highly fertile soils of the floodplains and Amazonian dark earths (ADE) along the middle Madeira River. Because different sets of varieties are grown in each soil type, and there are agronomic similarities between ADE and floodplain varieties, it was hypothesized that varieties grown in ADE and floodplain were more closely related to each other than either is to varieties grown in Oxisols. We tested this hypothesis evaluating the intra-varietal genetic diversity and the genetic relationships among manioc varieties commonly cultivated in Oxisols, ADE and floodplain soils. Genetic results did not agree with ethnobotanical expectation, since the relationships between varieties were variable and most individuals of varieties with the same vernacular name, but grown in ADE and floodplain, were distinct. Although the same vernacular name could not always be associated with genetic similarities, there is still a great amount of variation among the varieties. Many ecological and genetic processes may explain the high genetic diversity and differentiation found for bitter manioc varieties, but all contribute to the maintenance and amplification of genetic diversity within the manioc in Central Amazonia.

Soil-landscape relationship in a chronosequence of the middle Madeira River in southwestern Amazon, Brazil

High temperatures and rainfall prevail in the Brazilian Amazon, but some areas have soils with high clay mineral contents of 2:1, and there is limited information concerning their properties. Therefore, it is important to study the soil formation and understand the environmental conditions in which they were formed. This study aimed to investigate the physical, chemical and mineralogical properties of the soil in relation to the environmental factors acting on a chronosequence in the Late Pleistocene sediments of the Middle Madeira River. Soil profiles were selected on three alluvial terraces. Morphological, physical, chemical, mineralogical, X-ray fluorescence, TEM and SEM characterizations were performed. The soils that exhibited a clayey texture, acidic reaction, low values of exchangeable bases and high values of aluminum had profiles containing a considerable presence of 2:1 clay minerals, especially illite, vermiculite, mica-vermiculite, hydroxyl-interlayered vermiculite and pyrophyllite. Soil mineralogy indicated that these soils were recently weathered, where the low values of sum of bases correspond to the low presence of these cations in the parent material. Meanwhile, high values of exchangeable aluminum were derived from the pyrophyllite alteration, different parent material and 2:1 clay minerals recent alteration. Therefore, the parent material, presence of amorphous silica, different climate conditions in the past and current drainage restriction contribute to the slow alteration rate of 2:1 clay minerals of the soils of the humid tropical Amazon environment.

Convergent adaptations: bitter manioc cultivation systems in fertile anthropogenic dark earths and floodplain soils in Central Amazonia.

Shifting cultivation in the humid tropics is incredibly diverse, yet research tends to focus on one type: long-fallow shifting cultivation. While it is a typical adaptation to the highly-weathered nutrient-poor soils of the Amazonian terra firme, fertile environments in the region offer opportunities for agricultural intensification. We hypothesized that Amazonian people have developed divergent bitter manioc cultivation systems as adaptations to the properties of different soils. We compared bitter manioc cultivation in two nutrient-rich and two nutrient-poor soils, along the middle Madeira River in Central Amazonia. We interviewed 249 farmers in 6 localities, sampled their manioc fields, and carried out genetic analysis of bitter manioc landraces. While cultivation in the two richer soils at different localities was characterized by fast-maturing, low-starch manioc landraces, with shorter cropping periods and shorter fallows, the predominant manioc landraces in these soils were generally not genetically similar. Rather, predominant landraces in each of these two fertile soils have emerged from separate selective trajectories which produced landraces that converged for fast-maturing low-starch traits adapted to intensified swidden systems in fertile soils. This contrasts with the more extensive cultivation systems found in the two poorer soils at different localities, characterized by the prevalence of slow-maturing high-starch landraces, longer cropping periods and longer fallows, typical of previous studies. Farmers plant different assemblages of bitter manioc landraces in different soils and the most popular landraces were shown to exhibit significantly different yields when planted in different soils. Farmers have selected different sets of landraces with different perceived agronomic characteristics, along with different fallow lengths, as adaptations to the specific properties of each agroecological micro-environment. These findings open up new avenues for research and debate concerning the origins, evolution, history and contemporary cultivation of bitter manioc in Amazonia and beyond.

A Chiroptera preliminary survey in the middle Madeira River region of Central Amazonia, Brazil

Western Brazilian Amazonia is considered to be more bat species-rich than areas in other parts of the biome. However, the middle Madeira River region has been pointed out as a lacuna for mammal inventories, and information on its bat diversity is still scarce. I present here a bat fauna survey of the middle Madeira River region and its main tributary, the Aripuanã River. Using mist nets [4626 meter net.hours (m.h)], I surveyed ten riverine village sites, four primary forest sites and one secondary forest site distributed along the margins of both rivers. In 22 nights during the dry and rainy seasons, 356 bats of 30 species and five families were recorded. The bat species-richness was similar along both rivers, with 24 species in the Madeira sites and 23 in the Aripuanã. Vampyriscus bidens and Mesophylla macconnelli were the most captured bats in the village sites along the Aripuanã River, whereas all captures of Artibeus planirostris occurred along Madeira River villages. A new record for Vampyressa thyone in the Amazonas state is reported, approximately 500 km southeast of the nearest record.

Genetic structure of traditional varieties of bitter manioc in three soils in Central Amazonia

Manioc is the most important food crop that originated in Amazonia. Many studies have increased our understanding of its evolutionary dynamics under cultivation. However, most of them focused on manioc cultivation in environments with low soil fertility, generally Oxisols. Recent ethnobotanical observations showed that bitter manioc also performs well in high fertility soils, such as Amazonian dark earths (ADE) and the floodplain. We used 10 microsatellite loci to investigate the genetic diversity and structure of bitter manioc varieties grown in different soil types in communities of smallholder farmers along the middle Madeira River in Central Amazonia. The genetic diversity of some sweet varieties and seedlings was also evaluated. Adult individuals showed higher levels of genetic diversity and smaller inbreeding coefficients (A ( R ) = 5.52, H ( O ) = 0.576, f = 0.086) than seedlings (A ( R ) = 4.39, H ( O ) = 0.421, f = 0.242). Bitter manioc varieties from the floodplain showed higher levels of genetic diversity (A ( R ) = 5.19, H ( O ) = 0.606) than those from ADE (A ( R ) = 4.45, H ( O ) = 0.538) and from Oxisols (A ( R ) = 4.15, H ( O ) = 0.559). The varieties grown in the floodplain were strongly differentiated from the varieties grown in Oxisols (F ( ST ) = 0.093) and ADE (F ( ST ) = 0.108), suggesting important genetic structuring among varieties grown in the floodplain and upland soils (ADE and Oxisols). This is the first time that genetic divergence of bitter manioc varieties in cultivation in different Amazonian soils in a small geographic area is reported.

Crop Diversity on Anthropogenic Dark Earths in Central Amazonia

A recent archaeological survey demonstrates that one of the most durable of all forms of pre-Columbian landscape transformation, Amazonian Dark Earths (ADE; soils formed by pre-Columbian settlement), are widespread along the course of the Madeira River, Central Amazonia, Brazil. We hypothesize that processes of crop cultivation and management by human populations today in landscapes that were intensively transformed during the pre-Columbian period will diverge from those in environments where human agency has not left such a heavy footprint. In order to test this hypothesis, we compare bitter manioc fields, homegardens and secondary forests on ADE with those on non-anthropogenic soils along the lower and middle Madeira River. We demonstrate that crop species and landrace populations diverge on anthropogenic and non-anthropogenic soils as a result of the interaction between human selection and management, soil physical and chemical properties, and plant responses over time. Hence, crop species selection and abundance and therefore agrobiodiversity is contingent on anthropogenic soils in Central Amazonia.

Caracterização e classificação de terras pretas arqueológicas na Região do Médio Rio Madeira

Apesar da existência de muitas pesquisas sobre as Terras Pretas Arqueológicas, poucos são os trabalhos que têm procurado entender e esclarecer dúvidas sobre a gênese e o comportamento destes solos. Dessa maneira, o objetivo deste trabalho foi caracterizar e classificar terras pretas arqueológicas de quatro sítios na Região do Médio Rio Madeira. Nesses locais, foram abertas trincheiras e os perfis caracterizados morfologicamente e amostrados. Foram realizadas as seguintes análises físicas: textura, argila dispersa em água, densidades do solo e das partículas, porosidade total e condutividade hidráulica saturada. As análises químicas constaram de: pH em água e KCl, cátions trocáveis, Al trocável, P disponível, acidez titulável (H+Al) e C orgânico, Al2O3 e Fe2O3 e SiO2 extraídos pelo método do ataque sulfúrico, e teor de C das substâncias húmicas. Para determinar óxidos de Fe foram utilizados o ditionito-citrato-bicarbonato (Fed) e o oxalato ácido de amônio (Feo). As análises mineralógicas das frações areia, silte e argila foram feitas por difratometria de raios-X. Os perfis foram classificados no Sistema Brasileiro de Classificação de Solos como: Argissolo Vermelho Amarelo, Argissolo Acinzentado e Argissolo Amarelo. Os solos apresentaram horizonte A antrópico com características químicas e de profundidade semelhantes, sugerindo certa similaridade dos fatores antrópicos que promoveram sua formação. Os horizontes antrópicos de todos os perfis amostrados na região tinham caráter eutrófico e teores altos a muito altos de fósforo disponível, sempre maiores que os dos horizontes subjacentes. Sugere-se a inclusão do subgrupo antrópico no SiBCS.

Homegardens on Amazonian Dark Earths, Non-anthropogenic Upland, and Floodplain Soils along the Brazilian Middle Madeira River Exhibit Diverging Agrobiodiversity1

Homegardens on Amazonian Dark Earths, Non-anthropogenic Upland, and Floodplain Soils along the Brazilian Middle Madeira River Exhibit Diverging Agrobiodiversity. We test the hypothesis that the agrobiodiversity associated with homegardens on three different soils—upland Amazonian Dark Earths (ADE) and Oxisols (OX), and Fluvent Entisols (FL)—commonly found along the middle Madeira River in the municipality of Manicore, Amazonas State, Brazil, is different due to the contrasting biotic, abiotic, and cultural settings specific to each of these soils. Using data from interviews with 63 farmers about food and utility species, we compare structural and floristic characteristics of homegarden agrobiodiversity. The density of individuals is higher on ADE than on the other soils (mean ± standard deviation: 715 ± 363 on ADE, 474 ± 283 on OX, 642 ± 399 on FL). ADE and OX have higher species richness (28.2 ± 5.6 on ADE, 25 ± 3.7on OX, 23.6 ± 5 on FL), while ADE and FL have a greater degree of domestication (2 ± 0.6 on ADE, 1.3 ± 0.5 on OX, 2.3 ± 0.6 on FL). ADE and OX have greater proportions of richness, density, and coverage composed of South American species, while FL has greater proportions of richness and density composed of Old World species. ADE has higher proportions of density and coverage of Mesoamerican species. Floristic composition is also different between soils: ADE occupies an intermediate position, composed of species associated with each of the other soil types and species that are most common on ADE. These differences in agrobiodiversity emerge through the interaction of human agency, plant responses, and the unique properties of soils in relation to socioeconomic and historical trajectories over time.

Secondary Forests on Anthropogenic Soils of the Middle Madeira River: Valuation, Local Knowledge, and Landscape Domestication in Brazilian Amazonia

Secondary Forests on Anthropogenic Soils of the Middle Madeira River: Valuation, Local Knowledge, and Landscape Domestication in Brazilian Amazonia. Anthropogenic forests and soils are widespread throughout Amazonia and are the product of the landscape domestication process carried out by Amazonian societies since pre-Colombian times. Areas of Terra Preta de Indio (TPI, Amazonian Dark Earths) are recognized by local rural residents and associated with specific forms of use and management of these soils and associated secondary forests. We used a quantitative approach to investigate how secondary forests on TPI are recognized and used by local residents along the middle Madeira River, Central Amazonia. Sixty-two residents were interviewed in three riverside communities and listed the ethnospecies and their uses in secondary forests on TPI and on non-anthropogenic soils (NAS). Local residents mentioned more ethnospecies on TPI (mean ± standard deviation: 19.5 ± 8.9) than on NAS (17.4 ± 8.5), and the use value of the environment to the informants (UVia) was higher on TPI (19 ± 5.7) than on NAS (16.2 ± 6.0). Eleven ethnospecies were classified as anthropogenic soil indicators, among which three intensively used palms are widely recognized as indicators of anthropogenic areas and two are domesticated to some degree. The intimate and lasting interactions between humans and TPI have favored the maintenance of secondary forests in these domesticated landscapes with a diverse assemblage of useful and domesticated species. Rural residents in Amazonia recognize these forests as an important source of food and other resources. The use, management, and traditional knowledge related to these domesticated landscapes may provide useful information for the understanding of Amazonian historical ecology and for the design of more efficient biodiversity management and conservation plans.

Caboclo Horticulture and Amazonian Dark Earths along the Middle Madeira River, Brazil

This article examines the relationship between Amazonian Dark Earths (ADE) and Caboclo horticultural knowledge and practice along the middle Madeira River (the biggest whitewater tributary of the Amazon) in the municipality of Manicore, Amazonas State, Brazil. ADE are fertile anthropogenic (human-made) soils that are found in many areas of the Amazon region. The formation of ADE is a legacy of Amerindian settlement patterns, mostly during the late pre-Columbian period (2000–500 bp). The primary users of ADE in the Central Amazon today are Caboclos, traditional Amazonian people of heterogeneous origins. The multi-sited ethnography presented here demonstrates that Caboclos have developed a repertoire of local knowledge surrounding the cultivation of their staple crop, bitter manioc, in these soils. This revolves around a local theory of “weakness” and “strength” used to describe different sets of bitter manioc landrace traits and their responses to planting in different kinds of soil and fallow ages. This local theory has developed in the context of a regional historical ecology that has enabled the conservation and generation of such horticultural knowledge. I conclude that these notions of strength and weakness shape divergent loci of bitter manioc genetic traits and co-evolutionary dynamics between people and plants in the cultivation of bitter manioc in different soil types.

The Diversity of Bitter Manioc (Manihot Esculenta Crantz) Cultivation in a Whitewater Amazonian Landscape

While bitter manioc has been one of the most important staple crops in the central Amazon for thousands of years, there have been few studies of its cultivation in the fertile whitewater landscapes of this region. Anthropological research on bitter manioc cultivation in the Amazon has focused almost exclusively on long-fallow shifting cultivation in marginal upland areas of low soil fertility. This has contributed to the persistence of the oversimplified notion that because bitter manioc is well adapted to infertile upland soils; it cannot yield well in alluvial and/or fertile soils. I hypothesized that bitter manioc cultivation would be well adapted to the fertile soils of the whitewater landscapes of the central Amazon because of the centrality of this crop to subsistence in this region. In this article, I examine one such whitewater landscape, the middle Madeira River, Amazonas, Brazil, where smallholders cultivate bitter manioc on fertile Amazonian Dark Earths (ADE) and floodplain soils, and on infertile Oxisols and Ultisols. In this region, cultivation on fertile soils tends to be short-cycled, characterised by short fallowing (0–6 years) and shorter cropping periods (5–12 months) with a predominance of low starch fast maturing “weak” landraces. By contrast, cultivation on infertile soils is normally long-cycled, characterised by longer fallows (&gt;10 years) and longer cropping periods (1–3 years) with a predominance of high starch slow maturing “strong” landraces. This diversity in bitter manioc cultivation systems (landraces, fallow periods, soils) demonstrates that Amazonian farmers have adapted bitter manioc cultivation to the specific characteristics of the landscapes that they inhabit. I conclude that contrary to earlier claims, there are no ecological limitations on growing bitter manioc in fertile soils, and therefore the cultivation of this crop in floodplain and ADE soils would have been possible in the pre-Columbian period.