One sixth of Amazonian tree diversity is dependent on river floodplains

Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.Naturali

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

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

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, 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 organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected 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 lost

Old-growth Neotropical forests are shifting in species and trait composition

Tropical forests have long been thought to be in stable state, but recentinsights indicate that global change is leading to shifts in forest dynamics and species composition. These shifts may be driven by environmental changes such as increased resource availability, increased drought stress, and/or recovery from past disturbances.The relative importance of these drivers can be inferred from analyzing changes in trait values of tree communities. Here, we evaluate a decade of change in species and trait composition across five old-growth Neotropical forests in Bolivia, Brazil, Guyana, and Costa Rica that cover large gradients in rainfall and soil fertility. To identify the drivers of compositional change, we used data from 29 permanent sample plots and measurements of 15 leaf, stem, and whole-planttraits that are important for plant performance and should respond to global change drivers. We found that forests differ strongly in their community-meantrait values, resulting from differences in soil fertility and annual rainfall seasonality. The abundance of deciduous species with high specific leaf areaincreases from wet to dry forests. The community-mean wood density is high in the driest forests to protect xylem vessels against drought cavitation, and is high in nutrient-poor forests to increase wood longevity and enhance nutrient residence time in the plant. Interestingly, the species composition changed over time in three of the forests, and the community-mean wood density increased and the specific leaf area decreased in all forests, indicating that these forests are changing toward later successional stages dominated by slow-growing,shade-tolerant species. We did not see changes in other traits that could reflect responses to increased drought stress, such as increased drought deciduousnessor decreased maximum adult size, or that could reflect increased resource availability (CO2, rainfall, or nitrogen). Changes in species and trait composition in these forests are therefore most likely caused by recovery from past disturbances. These compositional changes may also lead to shifts in ecosystem processes, such as a lower carbon sequestration and “slower” forest dynamics

Compatibilidade entre tratamento de sementes de amendoim com fungicidas, sobrevivência de Rhizobium e nodulação Compatibility between peanut seed preservation with fungicides, survival of rhizobia and nodulation

Conduziu-se um experimento para testar a compatibilidade dos fungicidas captã, PCNB e tirã com a inoculação de sementes de amendoim, cujo tratamento se efetuou simultaneamente com a inoculação ou dez dias antes desta. No momento da inoculação e quatro horas após, fez-se uma contagem de Rhizobium nas sementes, pelo método da diluição e inoculação de gotas em placas, mantendo-se um controle sem aplicação de fungicida. Para se estudar o efeito dos tratamentos na nodulação e fixação, plantaram-se as sementes em solo esterilizado, avaliando-se a nodulação e o teor de ureídeos nas folhas. Somente o captã aplicado simultaneamente à inoculação foi prejudicial à sobrevivência bacteriana nas sementes. De maneira geral, a aplicação dos fungicidas simultaneamente à inoculação mostrou-se prejudicial em relação à antecipada.<br>An experiment was carried out to test the compatibility between peanut seed treated with the fungicides captan, PCNB and thiram with rhizobia inoculation. The application of the fungicides was done either simultaneously or ten days before the inoculation of the seeds. A control, without inoculation, was included. Countings of rhizobia on the seed were made immediately after inoculation and four hours after, by dilution and drop plating technique. In order to study the effect of treatments on nodulation and nitrogen fixation, treated and untreated seeds were planted in gamma irradiated soil and nodulation and leaf ureid content were later evaluated. It was observed that only captan applied to the seed simultaneously with inoculation was significantly deleterious to survival of the rhizobia. In general the application of the fungicide ten days before inoculation caused no significant harmfull effect to survival of rhizobia on the seed