34 research outputs found

    Frugivoria e ictiocoria em uma √°rea de v√°rzea na Amaz√īnia Central brasileira

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    The aim of the study was to investigate the interaction between fish and plants through analysis of seeds taken entire from the digestive tract of fish, sampled in the Catal√£o Lake, Central Brazilian Amazon. Samples were collected in 2014 during periods corresponding to the flooding, peak of flood and receding waters. Seeds were consumed by 148 fish individuals, belonging to 14 species, two orders and six families, among them some migratory species, such as Colossoma macropomum, Pterodoras granulosus and species belonging to the genera Brycon and Triportheus. The most intense consumption was observed in May, June and July, corresponding to periods of flooding and early receding of waters. Eighteen plant species belonging to 16 families were identified. Cecropia spp., Ficus insipida and Laetia corymbulosa were the most abundant in the fish diets. Triportheus albus (n=33), Triportheus auritus (n=27) and Colossoma macropomum (n=19) had the largest number of sampled specimens containing seeds in their digestive tract. Seeds of 18 species were sown in a greenhouse with soil from v√°rzea, in order to verify their viability; of these, only seeds of two species (Bactris riparia and Senna alata) did not germinate. For analysis of percentage, germination time and speed, were used two plant species, Cecropia spp. and Laetia corymbulosa, since they were the species most consumed by three species (Triportheus albus, T. angulatus and T. auritus), which were amongst the most abundant fish species in the study area. The percentage, speed and average time of germination of these two species did not differ from seeds taken from the stomach or intestine of the fishes evaluated. The same germination parameters were calculated for a subset of seeds taken only in the intestines (n= 100 seed) and those derived directly from the mother plants (n= 100). The results indicated significant difference for both species among the subsets of seeds taken from the intestines and from the mother-plants. Seeds subjected to the digestive process of the fish showed no germination increment. However, the fact that there were found viable seeds in the digestive tract of fishes with migratory habits, suggests that ichthyochory should be considered an highly important vector of seed dispersal in the v√°rzeas.O objetivo do estudo foi investigar a intera√ß√£o entre peixes e plantas por meio da an√°lise de sementes retiradas inteiras do trato digest√≥rio de peixes capturados no lago Catal√£o, Amaz√īnia Central, Brasil. As coletas foram realizadas no ano de 2014 durante os per√≠odos correspondentes √† enchente, cheia e vazante. Consumiram sementes 148 exemplares de peixes pertencentes a 14 esp√©cies, duas ordens e seis fam√≠lias, entre elas algumas de h√°bito migrat√≥rio, como Colossoma macropomum, Pterodoras granulosus, e esp√©cies dos g√™neros Brycon e Triportheus. O consumo mais intenso foi verificado nos meses de maio, junho e julho, correspondentes aos per√≠odos de cheia e in√≠cio da vazante. Foram identificadas 18 esp√©cies vegetais pertencentes a 16 fam√≠lias. Cecropia spp., Ficus insipida e Laetia corymbulosa apresentaram a maior frequ√™ncia de ocorr√™ncia de consumo por peixes. Triportheus albus (n=33), Triportheus auritus (n=27) e Colossoma macropomum (n=19) tiveram o maior n√ļmero de exemplares capturados com sementes. As sementes foram semeadas em casa de vegeta√ß√£o sobre solo de v√°rzea, com o objetivo de verificar a sua viabilidade; dessas, apenas as sementes de duas esp√©cies (Bactris riparia e Senna alata) n√£o germinaram. Para an√°lise de porcentagem, velocidade e tempo m√©dio de germina√ß√£o, foram utilizadas duas esp√©cies, Cecropia spp. e Laetia corymbulosa, por terem sido as esp√©cies mais consumidas por tr√™s das esp√©cies de peixes mais abundantes na √°rea de estudo, Triportheus albus, T. angulatus e T. auritus. A porcentagem, a velocidade e o tempo m√©dio de germina√ß√£o dessas duas esp√©cies n√£o diferiram entre sementes retiradas do est√īmago e do intestino dos peixes. Os mesmos par√Ęmetros germinativos foram calculados para um subconjunto das sementes retiradas somente do intestino (n=100 sementes) e daquelas oriundas diretamente das plantas-m√£e (n=100). Os resultados indicaram diferen√ßa significativa para as duas esp√©cies entre subconjuntos das sementes retiradas dos intestinos e das plantas-m√£e. Sementes submetidas ao processo digest√≥rio dos peixes n√£o apresentaram incremento germinativo. Entretanto, o fato de terem sido encontradas sementes vi√°veis no trato digest√≥rio de peixes com h√°bito migrat√≥rio, sugere que a ictiocoria deve ser considerada um vetor de elevada importante na dispers√£o de sementes na v√°rzea

    The shadow of the Balbina dam: A synthesis of over 35 years of downstream impacts on floodplain forests in Central Amazonia

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    1. The Balbina hydropower dam in the Central Amazon basin, established in the Uatum√£ River in the 1980s, is emblematic for its socio‚Äźenvironmental disaster. Its environmental impacts go far beyond the reservoir and dam, however, affecting the floodplain forests (igap√≥) in the downstream area (dam shadow), which have been assessed using a transdisciplinary research approach, synthesized in this review. 2. Floodplain tree species are adapted to a regular and predictable flood pulse, with high‚Äź and low‚Äźwater periods occurring during the year. This was severely affected by the operation of the Balbina dam, which caused the suppression of both the aquatic phase at higher floodplain elevations and the terrestrial phase at lower floodplain elevations (termed the ‚Äėsandwich effect‚Äô). 3. During the period of construction and reservoir fill, large‚Äźscale mortality already occurred in the floodplains of the dam shadow as a result of reduced stream flow, in synergy with severe drought conditions induced by El Ni√Īo events, causing hydraulic failure and making floodplains vulnerable to wildfires. 4. During the operational period of the dam, permanent flooding conditions at low topographical elevations resulted in massive tree mortality. So far, 12% of the igap√≥ forests have died along a downstream river stretch of more than 125 km. As a result of flood suppression at the highest elevations, an encroachment of secondary tree species from upland (terra firme) forests occurred. 5. More than 35 years after the implementation of the Balbina dam, the downstream impacts caused massive losses of macrohabitats, ecosystem services, and diversity of flood‚Äźadapted tree species, probably cascading down to the entire food web, which must be considered in conservation management. 6. These findings are discussed critically, emphasizing the urgent need for the Brazilian environmental regulatory agencies to incorporate downstream impacts in the environmental assessments of several dam projects planned for the Amazon region.Additional co-authors: Fl√°via Machado Durgante, Aline Lopes, Susan E. Trumbore, Hans ter Steege, Adalberto Luis Val, Wolfgang J. Junk, Maria Teresa Fernandez Piedad

    Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

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    Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ‚Č•‚ÄČ9.55‚ÄČcm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

    Mapping density, diversity and species-richness of the Amazon tree flora

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    Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution

    Consistent patterns of common species across tropical tree communities

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    Trees structure the Earth‚Äôs most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10‚ÄČcm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth‚Äôs 800 billion tropical trees with trunk diameters of at least 10‚ÄČcm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world‚Äôs most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

    Pervasive gaps in Amazonian ecological research

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    Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5‚Äď7 vast areas of the tropics remain understudied.8‚Äď11 In the American tropics, Amazonia stands out as the world‚Äôs most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13‚Äď15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon‚Äôs biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region‚Äôs vulnerability to environmental change. 15%‚Äď18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

    Pervasive gaps in Amazonian ecological research

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    Unraveling Amazon tree community assembly using Maximum Information Entropy: a quantitative analysis of tropical forest ecology

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    In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics

    Unraveling Amazon tree community assembly using Maximum Information Entropy: a quantitative analysis of tropical forest ecology

    Get PDF
    In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics
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