ABSTRACT The site index (SI) was evaluated in Guazuma crinita plantations for the Aguaytía River region, Ucayali, Peru, with seedlings from 200 open-pollinated families from 14 sites using a randomized block design in three sectors of the basin. At 48 months, the height (H), diameter at breast height (DBH), and the number of branches with leaves (C/Leaf) and without leaves (S/Leaf) of the trees in 11 plantations were measured. The population means were 9.8 cm (DAP), 1139.6 cm (H), 12.4 branches (C/Leaf) and 2.4 branches (S/Leaf), distributed in four phenotypic groups (G1, G2, G3, G4). Groups G1 and G3 presented greater growth in DAP and H. The correlations between SI and edaphic variables show a significantly positive association with calcium (Ca+2: 0.62), cation exchange capacity (CEC: 0.67), magnesium (Mg+2: 0.61), and pH (059), and non-significant negative association with texture (-0.38), sand (-0.38), potassium (K+: -0.15) and aluminum (Al+3: -0.39). Physiographic and climatic correlations indicate a significantly strong association between SI and elevation (0.85) and precipitation (0.97), while correlations between SI and DBH, H, basal area (BA) and volume (V) They have a high significance of 0.8, 0.7, 0.7 and 0.8, respectively. The middle and upper sectors of the basin present more favorable conditions for the development of commercial plantations that improve with the selection of the best phenotypic groups from the Río Aguaytía, San Alejandro, Río Curimana and Von Humboldt collection sites.
ABSTRACT Agroforestry systems (AFS) are an alternative for combining environmental services and food production with tree cultivation, but there is a lack of published studies on their wood quality. This study aimed to evaluate the surface properties of African mahogany, Freijó, Paricá, and Teak woods produced in AFS in the Amazonia. Anatomical characteristics, FTIR spectroscopy, colorimetry, roughness, contact angle, and wettability in the longitudinal-radial and tangential planes were evaluated. The woods presented non-uniform diffuse porosity, with solitary and multiple vessels, except for Teak, which showed semi-porous ring porosity. Woods rays were multiseriate and heterogeneous, except for Teak, whose rays were homogeneous. The largest average vessel diameter was observed in Teak (~180 µm) and the smallest in A. mahogany (~98 µm). The frequency of vessels was higher in A. mahogany (~12 vessels mm-¹) and lower in Paricá (~5.5 vessels mm-¹). In FTIR, A. mahogany showed intense peaks at 1,193 cm-¹ (triterpenoids), while Teak had peaks at 1,700 and 1,145 cm-¹ (tectoquinone). A. mahogany and Teak presented pinkish and yellowish-olive colors, respectively, while Paricá and Freijó had pinkish-grey tones. Teak presented the lowest roughness and A. mahogany the highest, while Freijó and Paricá exhibited intermediate values. The highest contact angle was recorded in A. mahogany (~115° for urea-formaldehyde and ~70° for varnish), while the lowest was observed in Paricá. The evaluated woods have surface properties suitable for furniture and boards, and fine sandpaper is recommended for higher-quality finishes.
ABSTRACT One of the eleven species of nocturnal primates, Aotus vociferans occurs in Colombia. It lives in different types of forests, agroecosystems and peri-urban areas and is listed as Least Concern due mainly to its wide distribution and its presumed large populations that have been little studied due to their nocturnal habits. However, further studies are needed to confirm the current status of its populations throughout its range, since despite its habitat flexibility, anthropogenic activities and illegal trafficking have led to changes in population densities and modification of the sites used by this species. To estimate population density and proportion of used area of A. vociferans in a secondary forest in the Colombian Andean Amazonian foothills, specifically in Florencia-Caquetá, we used the distance sampling method with linear transects and occupancy models. Sampling was carried out along 20 transects in a 25-ha area from November 2022 until February 2023, from 18:00 to 00:30 hours. The estimated population density for A. vociferans in the area was 47.34 ind km-2. The occupation probability was 0.56, and 11 transects presented a probability of 1.0 of being used by A. vociferans. The population density was similar to other estimations for Aotus in secondary, floodplain, and mature forest, but was higher than that recorded in highland forests. The occurrence probability might be associated with the presence of plant species from the families Anonaceae, Anacardiaceae, Arecaceae, Euphorbiaceae, Melastomataceae and Solanaceae, which were observed in Aotus diet, but this hypothesis must be tested with a robust plant sampling. We report the highest known density for this species in the Amazon region and provide the first estimate of the proportion of area used by A. vociferans.
ABSTRACT A lifetime of near-daily observations, as opposed to scientific sampling expeditions that are often limited in time and space, makes Local Ecological Knowledge (LEK) an extremely valuable source of information for understanding rare, threatened, or cryptic species. This study documents LEK about the Amazonian manatee (Trichechus inunguis) in the Purus River basin, Central Amazon. Based on interviews with 104 residents from 30 riverine communities, we access local manatee experts’ perceptions of social behavior, activity patterns, habitat use, diet, and species conservation. LEK provided insights into Amazonian manatee ecology, such as the persistence of manatees in floodplain environments during the low-water season and occasional fish consumption. The main threats reported were fishing nets and hunting. However, extreme drought events driven by climate change were frequently mentioned, as these increase vulnerability to both hunting and food shortages. Most respondents strongly valued the role of Protected Areas in species protection and perceived a trend of population increase over the past two decades. Incorporating community-based observations and concerns into conservation strategies can therefore improve early-warning systems, guide habitat protection efforts, and support management of T. inunguis across protected and non-protected areas.
ABSTRACT Phenological cycles of tropical trees are shaped by environmental factors, yet the role of soil-water gradients on leaf phenology of equatorial forests remains poorly understood. We assessed the effects of water table depth (WT), classified into three categories based on Height Above Nearest Drainage (HAND) levels: Low (7-20m), representing shallow WT and greater root water access, Intermediate (21-60m) and High (61-89m), corresponding to deep WT and limited root water access, on leaf production and shedding of 547 canopy trees, monitored monthly for 52 years in Central Amazonia. Our results demonstrate that local hydrology is associated with phenological strategies and canopy persistence. Drier, high-HAND environments exhibited lower leaf flushing frequencies, a marked decline in mature leaves after 1990, and more frequent, prolonged canopy leaf-loss events. Conversely, wetter low-HAND sites showed higher leaf turnover and shorter flushing periods. Intra-annually, leaf flushing peaked during the dry season across all environments, but timing and intensity varied: low-HAND areas displayed bimodal patterns and earlier peaks (September), while high-HAND areas showed later peaks (October). Both deciduous and evergreen species responded to seasonal drought, but their temporal synchrony tended to be stronger in higher HAND environments, where climatic constraints are more severe. In wetter sites, weaker synchrony suggests reduced seasonal limitation on leaf production. We conclude that hydrological gradient and leaf habit jointly shape phenological dynamics, with drier environments experiencing greater canopy loss and tighter seasonal constraints on leaf renewal. These findings highlight the importance of local hydrological niches in forest responses to environmental change.
ABSTRACT Despite its importance for the productive efficiency in Amazonian dairy systems, postpartum metabolism and uterine recovery in crossbred cows raised in this biome remain poorly understood. We compared the biological activity of the uterus and the metabolism between primiparous and multiparous crossbred dairy cows (B. indicus x B. taurus) in southwestern Amazonia. Cows were divided by parity order into primiparous (n = 8), and multiparous (n = 10) and were evaluated from parturition to 50 days in milk (DIM) for metabolic and reproductive variables. Uterine tissue was collected using the cytobrush technique to evaluate uterine inflammation and receptivity. Parity did not significantly affect energy metabolism, and multiparous cows had lower uterine inflammatory response associated with lower relative expression of IL-6 and higher relative expression of IL-10. We conclude that parity has little effect on the puerperium of crossbred dairy cows, which were considered healthy by 50 DIM.
Abstract The functioning of tropical secondary forests is strongly influenced by the availability of water and nutrients, which regulate litter production, decomposition, and nutrient cycling. In Amazonian landscapes subjected to shifting cultivation, repeated disturbance and resource depletion may generate long-lasting legacy effects on ecosystem processes. Here, we evaluate whether such legacy effects persist in a secondary forest 14 years after the end of a large-scale field study that manipulated nutrient availability (via litter removal) and water supply (via irrigation) over eight years (1999-2007) in northeastern Brazilian Amazonia. We evaluated the enduring effects of water and nutrient management on litterfall, litter stock, and water holding capacity (WHC) 14 years after the conclusion of the experiment (2021), as well as the influence of meteorological variables on litterfall. Data collection took place monthly throughout 2021, and litter stock and WHC were measured during the months with the highest and lowest precipitation according to climatological averages. The total litterfall over year ranged from 10.48 ± 0.31 Mg ha-1 to 11.61 ± 0.29 Mg ha-1, with the highest litter stock observed in the dry season and the lowest WHC in the rainy season. Meteorological variables and treatments were not significant predictors of litterfall or litter stock variation, indicating weak direct climatic control over litter dynamics at this successional stage. The results suggest that secondary forests in Amazonia exhibit resilience after a prolonged stress (litterfall removal) and the ability to optimize resources following shifting cultivation in subsistence agriculture.
ABSTRACT Miconia kallei has been collected twice, in the Brazilian states of Amazonas and Rondônia. The most prominent character in this species is the longitudinal anther dehiscence, which also appears in 14 other species in Brazil. It differs from these other species by the leaves that are sessile or with very small petioles up to 3 mm, with a cordate base, and stellate-stipitate or dendritic trichomes on the abaxial surface, inflorescences with accessory branches, the truncate calyx with a 0.6-0.8 mm long tube and the adaxial surface covered with tiny glandular projections, and the stamens with the connective prolonged below the thecae, bearing complex appendages, and the dehiscence area comprising 100% of the thecae length. The small number of collections is insufficient to suggest an extinction risk assessment but for “data deficient”.
ABSTRACT Temporal partitioning of resources can shape biological assemblages on a nycthemeral scale. This phenomenon may arise from differences in activity of species or ecological interactions. This study investigated fish assemblages of aquatic herbaceous banks of Catalão Lake, Central Amazon, during daytime and nighttime periods, considering trophic position and activity pattern of species. Thirty-six samples were collected using a seine net (18 daytime hauls and 18 nighttime hauls). Eighty species were recorded, including 56 diurnal and 24 nocturnal species. Species richness, abundance, and exclusivity were higher at night. Non-piscivorous fishes dominated both diel phases, whereas piscivorous showed slightly higher relative abundance during the day. Results suggest that aquatic herbaceous banks are habitats temporally partitioned by fishes and function as zones of intense trophic activity. Temporal shifts in predator-prey composition and in diurnal and nocturnal species suggest that predator avoidance and intrinsic activity patterns are factors structuring these diverse assemblages.
ABSTRACT The Amazon is crucial for global environmental balance, including climate regulation, yet deforestation and wildfires increasingly threaten human health. This scoping review aims to map and synthesize evidence on the human health impacts of deforestation and wildfires in the Amazon and to identify key knowledge gaps. Empirical studies linking deforestation or wildfires to human health outcomes in the Amazon, published up to December 2023, were eligible for inclusion. Comprehensive searches were conducted in Web of Science, Scopus, and PubMed, supplemented by reference backward citation tracking. Data were extracted and synthesized to categorize findings by study characteristics (e.g., geographic scope, methodology) and health outcomes. The review included 108 studies identifying 41 distinct health outcomes. Malaria was the most researched, in 43.5% of the studies, showing strong associations with forest loss, alongside leishmaniasis (American tegumentary leishmaniasis and visceral leishmaniasis), evaluated in 13.9% of them. Biomass burning was linked to respiratory and cardiovascular diseases, particularly in Brazil, and was associated with genotoxicity and mutagenicity. Land-use change is therefore a critical driver of public health vulnerability in the Amazon. There is an urgent need for integrative analytical models and multisectoral policies within the One Health framework to mitigate these complex impacts.
ABSTRACT Cutaneous leishmaniasis is endemic in the state of Acre, western Amazonia, but natural vectors and reservoirs are poorly known. This study investigated Leishmania infection and blood meal sources in sand flies in the town of Sena Madureira. Sand flies were captured using CDC light and Shannon traps. Leishmania DNA was detected using PCR targeting hsp70; using PCR against cytb from engorged females’ blood samples. A total of 560 sand flies from 12 genera were collected, with Psychodopygus representing 56.6% of specimens.Leishmania DNA was detected in 12 samples, sequencing confirmed L. (Viannia) braziliensis infection in Nyssomyia fraihai and Psychodopygus hirsutus. Blood-meal testing identified cytb sequences matching human (5 flies), Tamandua tetradactyla (2 flies), and Cebus unicolor DNA (1 fly). This study provides new evidence ofLeishmaniacirculation in anthropic environments, highlighting potential risk for human infection and provides new methods for understanding leishmaniasis transmission.
ABSTRACT Effective management of tropical multispecies fisheries requires biologically grounded indicators that remain robust under data-limited conditions. This study evaluates the ratio between length at first sexual maturity (Lm) and maximum length (Lmax) as a comparative life-history metric for Amazonian fishes. Reproductive and biometric data from 123 commercially important species were compiled to assess variation in the Lm/Lmax ratio across geographic regions, habitat types, and life-history strategies. Although statistically significant regional differences were detected, values consistently clustered within a relatively narrow range, indicating functional convergence with bounded variability rather than strict invariance. This convergent pattern supports the use of the Lm/Lmax ratio as a heuristic reference for defining biologically meaningful size-based management thresholds for fisheries. By combining a lower limit based on maturity (Lm) with an upper limit for megaspawner protection (2/3 × Lmax + 10%), we propose the Target Capture Length (TCL) as an intermediate and operational reference point. The TCL framework translates life-history information into practical guidance for fisheries regulation, offering a simple and adaptable tool for improving sustainability in Amazonian fisheries under conditions of limited data availability.
ABSTRACT Environmental filtering associated with contrasting hydrological regimes may influence species persistence and the organization of network interactions in Amazonian forests. We evaluated how facultative (ant-extrafloral nectary) and obligate (ant-myrmecophyte) mutualisms differ between seasonally flooded igapó and unflooded terra-firme forests in Central Amazon. Across 14 plots, we recorded 446 interactions (273 facultative; 173 obligate) involving 72 plant and 72 ant species. Facultative interactions were richer and more frequent in terra-firme forests, forming significantly nested and modular networks, whereas igapó networks exhibited lower richness and no statistically significant network structure. In contrast, obligate interactions remained nested and modular in both forest types, despite substantial reductions in species richness in seasonally flooded igapó forests. The composition of ant-plant interaction pairs differed strongly between environments, mainly for obligate networks. Opportunistic ants nesting in myrmecophytes occurred almost exclusively in terra-firme and increased with myrmecophyte density. Overall, our results show that the structure and composition of ant-plant interactions differ markedly across flooded and unflooded Amazonian forests, with contrasting responses between facultative and obligate mutualisms. These findings reinforce the role of environmental heterogeneity in conserving ecological interactions in Amazonian forests.
ABSTRACT The Brazilian Amazon plays a vital role in global biodiversity, harboring species such as Banisteriopsis caapi, known for its cultural and medicinal significance. This study aimed to analyze the genetic diversity, with the use of ISSR (inter-simple sequence repeat) markers, of natural populations of mariri (B. caapi ethnovariety Tucunacá) in the Southern Amazon, as well as cultivated populations in agroforestry systems in Mato Grosso. The analysis revealed 92.3% polymorphism, with an average of 11.55 amplified bands per primer and a mean PIC of 0.466, considered moderately informative. Natural populations had greater genetic diversity (H = 0.323; I = 0.468) than cultivated ones (H = 0.164; I = 0.241), highlighting their role as genetic reservoirs. AMOVA indicated that 58% of the genetic variation occurs between populations, with low gene flow (Nm = 0.485) and strong genetic structuring (Fst = 0.582). The UPGMA (Unweighted Pair Group Method with Arithmetic Mean) dendrogram grouped populations into two main clusters, while Bayesian analysis identified three genetic clusters, reflecting geographic isolation and human management. Cultivated populations, particularly those at the Xingu Park Indigenous Territory, maintained significant genetic diversity, likely due to the use of seedlings from different origins. This study reinforces the importance of conserving natural populations, given increasing deforestation, and promoting sustainable management of cultivated populations to ensure species adaptability. Strategies such as in situ conservation and genetic diversity enhancement should be integrated to safeguard the ecological and cultural viability of B. caapi, ensuring the continuity of Ayahuasca’s traditional use by the communities dependent on this ethnovariety.
ABSTRACT The Amazon rainforest is one of the main global biodiversity hotspots where its diverse plant community provides optimal conditions and habitats for several soil microorganisms. Among these, Arbuscular Mycorrhizal Fungi (AMF) establishes important symbiotic relationships with many species of plants. We carried out a systematic bibliometric review of AMF in the Amazon, the mycorrhizal status of plant species, and a detailed analysis of the distribution of studies and occurrences of AMF species in Amazonian countries. The 110 studies examined had substantial spatial disparity, with research initiatives clustered in particular regions of Brazil and Peru, while information was totally absent for many Amazonian regions, including some countries in their entirety. The compiled studies encompassed 164 sampling sites in only 22 of the 55 Amazonian ecoregions. Furthermore, our analysis identified that most research focus was on assessing root colonization, morphological diversity, and spore quantification. These studies documented 143 AMF species, with the family Acaulosporaceae being most prevalent, and we highlight the description of 12 new species and four new genera from the Amazon. Only 181 plant species in 55 families were evaluated for symbiotic potential, of which 49 species (most in the Lecythidaceae) had no mycorrhizal association. This review underscores the necessity for expanded geographical coverage in inventories of Arbuscular Mycorrhizal Fungi, implementation of molecular approaches to expedite diversity assessment, and increased focus on plant-fungal symbiotic interactions throughout the Amazon.
ABSTRACT During a taxonomic review of Scleria sect. Hymenolytrum, herbarium specimens were analysed and identified as distinct from the currently accepted taxa within the section. Therefore, this study aimed to describe this new species - Scleria occulta L.Schneider & A.Gil, sp. nov., with emphasis on its morphoanatomical leaf traits. The original descriptions and nomenclatural types of the names involved were analysed together with morphological, anatomical, and micromorphological leaf data obtained from herbarium specimens, histological sections, clearing, and Scanning Electron Microscopy (SEM) images. The new species is known from only four specimens collected in Brazil and Venezuela, occurring in shaded environments within Ombrophilous forests. This study highlights the importance of integrative taxonomic approaches and access to virtual botanical collections for updating existing records and facilitating the description of new taxa. We identified new characters not previously highlighted as diagnostic for this group, including features of the staminate spikelets. Here, we provide illustrations and an identification key distinguishing the new species from morphologically similar taxa.
Secondary forests account for more than half of the planet's tropical formations. It is necessary to understand these forests in order to allow for efficient recovery and restoration processes of altered areas. In Rond & ocirc;nia state, in the Brazilian Amazon, where much of the natural vegetation cover has been altered over the last several decades, secondary forests have become particularly important. In this study, we selected species for restoration in Rond & ocirc;nia based on published work on secondary forests in the state, complemented with field collections by the authors. For each of the selected species, the successional category, dispersal syndrome and functional group was searched in the literature. Information regarding flowering and fruiting times as well as geographic distribution and habitats occupied in the state were obtained from vouchers deposited in herbaria. We listed 55 species from 49 genera and 23 families, of which 40% can be characterized as pioneers, 52.7% as secondary and 5.4% as climax species. Regarding functional group, 49% are diversity species and 34.5% are cover species. As for the dispersal syndrome, 60% are zoochoric, 16.3% anemochoric and 10.9% barochoric. Almost all of the species included in the list are common throughout the state and most are easy to recognize and identify. The species listed are present in all the main environments of Rond & ocirc;nia, and most are from terra firme forest. The listed species have the potential to play a fundamental role in the establishment and development of forests in altered and/or degraded areas in the state.
In a context of rapid deforestation and agricultural expansion, the GOD (Groundwater type, Overall lithology of aquifer, and Depth of groundwater) approach can be used to identify areas most susceptible to diffuse contamination of the aquifer. We applied this approach to evaluate the intrinsic vulnerability to pollution of the Alter do Ch & atilde;o Aquifer System, located in the Santar & eacute;m region (Par & aacute; State, Brazil). The parameters G (hydraulic confinement), O (lithology of overlying layers) and D (water table depth) were estimated using data from 41 boreholes from SIAGAS (Sistema de Informa & ccedil;& otilde;es de & Aacute;guas Subterr & acirc;neas) and spatialized with interpolation via kriging. Results reveal predominantly low to moderate vulnerability (79% of the study area), with critical zones near the Tapaj & oacute;s and Amazon rivers (high to extreme vulnerability, 2.2%). The presence of Belterra clay significantly reduces risks in the central plateau. Methodological limitations, associated to data availability, highlight the need for enhanced monitoring networks. This mapping provides a decision-support tool for integrated groundwater management in the Amazon.
Consumption of wild animals, especially the paca (Cuniculus paca), is a common practice among traditional communities. This rodent represents the main intermediate host for Echinococcus vogeli, the etiological agent of human polycystic echinococcosis, which is a zoonosis of growing public health concern in the region. This study aimed to investigate the occurrence of E. vogeli in livers of pacas slaughtered and consumed by resident traditional communities in the Western Brazilian Amazon. The research was observational and descriptive, conducted between May 2022 and December 2023 in traditional communities of Sena Madureira and Rio Branco (State of Acre, Brazil). Household interviews were performed to characterize hunting practices and dog management, along with the collection of paca livers for parasitological and molecular analysis (amplification and sequencing of a fragment of the cox1 mtDNA). Of the 78 families interviewed, 78% reported the practice of subsistence hunting. A total of 194 dogs were recorded, 83% of which actively participated in hunting activities, and 80% often consumed raw viscera, mostly from pacas. Among the 23 livers analyzed, 48% contained hydatid cysts (ranging from 1 to 13 cysts per liver), with E. vogeli infection confirmed based on morphology and PCR. The findings suggest that feeding dogs with raw viscera may facilitate the establishment of the domestic transmission cycle of E. vogeli, thereby increasing the risk of zoonotic infection. The close contact between humans, dogs, and infected paca livers highlight the urgent need for epidemiological surveillance and educational strategies aiming at the prevention of echinococcosis in endemic areas.
ABSTRACT Despite growing interest in microalgae for biodiesel, the quality parameters of biodiesel from Amazonian species remain largely unexplored. The rich biodiversity of the Amazon and the limited studies of its native microalgae make species such as Stigeoclonium sp. B23 promising candidates for sustainable and high-quality biodiesel. This study evaluated the effects of different nutritional conditions on fatty acid production and biodiesel quality in the Amazonian microalga Stigeoclonium sp. B23. Eight experimental conditions were established using modified BG-11 medium, combining the presence or absence of sodium nitrate with supplementation of sodium acetate (0.82 g L⁻¹) and/or sodium bicarbonate (0.42 g L⁻¹), to assess the impact of nitrogen limitation and alternative carbon sources. Among the tested experiments, the sodium nitrate depletion combined with supplementation of sodium acetate and sodium bicarbonate (Experiment 8) produced the most favorable fatty acid profile for biodiesel synthesis, with a cetane number of 77.1, oxidative stability of 7.07 h, and a saponification value of 127.3 mg g-1. Experiment 8 also showed a balanced composition of saturated (28.6%) and monounsaturated (6.4%) fatty acids. The biodiesel produced met all evaluated quality standards, including cetane number, iodine value, cold filter plugging point, and oxidative stability. These findings demonstrate the strong biotechnological potential of Stigeoclonium sp. B23 as a sustainable source of high-quality biodiesel.
