Giants of the Amazon: How does environmental variation drive the diversity patterns of large trees?

For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for example, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the diversity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high diversity of large trees. By contrast, variables associated with resources tend to govern tree diversity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high diversity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species diversity. Finally, we mapped general patterns of tree species diversity in the Brazilian Amazon, which differ substantially depending on size class.

Using near-infrared spectroscopy to discriminate closely related species: a case study of neotropical ferns.

Identifying plant species requires considerable knowledge and can be difficult without complete specimens. Fourier-transform near-infrared spectroscopy (FT-NIR) is an effective technique for discriminating plant species, especially angiosperms. However, its efficacy has never been tested on ferns. Here we tested the accuracy of FT-NIR at discriminating species of the genus Microgramma. We obtained 16 spectral readings per individual from the adaxial and abaxial surfaces of 100 specimens belonging to 13 species. The analyses included all 1557 spectral variables. We tested different datasets (adaxial + abaxial, adaxial, and abaxial) to compare the correct identification of species through the construction of discriminant models (Linear discriminant analysis and partial least squares discriminant analysis) and cross-validation techniques (leave-one-out, K-fold). All analyses recovered an overall high percentage (> 90%) of correct predictions of specimen identifications for all datasets, regardless of the model or cross-validation used. On average, there was > 95% accuracy when using partial least squares discriminant analysis and both cross-validations. Our results show the high predictive power of FT-NIR at correctly discriminating fern species when using leaves of dried herbarium specimens. The technique is sensitive enough to reflect species delimitation problems and possible hybridization, and it has the potential of helping better delimit and identify fern species.

Dataset on wood density of trees in ecotone forests in Northern Brazilian Amazonia.

Wood density is expressed by the ratio between dry weight and fresh volume of a sample piece. The value of this measure is an important variable for assessing wood functional properties, successional stages and biomass/carbon stock estimates in different terrestrial ecosystems. Wood density data were collected for tree species from ecotone forests of the northern Brazilian Amazonia. We sampled 680 individuals with stem diameter ≥10 cm. For each sampled individual measurements were taken for three stem variables: bark thickness (mm), bark density (g cm-3) and wood density (g cm-3). This dataset is intended to improve biomass and carbon estimates of forests in the northern ecotone region of Brazilian Amazonia, an area poorly known in terms of ecosystem dynamics.

Floristic composition in ecotone forests in northern Brazilian Amazonia: preliminary data.

BACKGROUND: Ecotone has been defined as "a multi-dimensional environmentally stochastic interaction zone between ecological systems with characteristics defined in space and time, and by the strength of the interaction" (Hufkens et al. 2009). This is a known concept to define transitional zones between two or more ecological communities, ecosystems or biotic regions. Ecotone forests, dispersed in northern Brazilian Amazonia, are natural formations which have been largely affected by anthropogenic impacts, such as deforestation and fire. Maracá Ecological Station, State of Roraima, Brazil, is a protected area with extensive representations of ecotone forests in this region of the Amazonia. Forest inventories and floristic surveys are important as they extend our knowledge (1) of forest structure and tree species composition and (2) of tree and palm species ecology in this region of the Amazonia. Both improve our ability to predict changes in plant diversity, considering the future scenarios of climate change in comparison with previous surveys performed in Maracá. NEW INFORMATION: We present a forest inventory carried out in 129 plots (10 m x 50 m; 6.45 ha in total) dispersed in a grid (5 km x 5 km) located in a forest zone ecotone in the eastern part of Maracá Ecological Station. All stems (tree + palm) with diameter at breast height ≥ 10 cm were recorded, identified and measured. A total of 3040 stems were recorded (tree = 2815; palm = 225), corresponding to 42 botanic families and 140 identified species. Seven families and 20 genera contained unidentified taxa (12.2%). Sapotaceae (735 stems; 10 species), Leguminosae (409; 24) and Rubiaceae (289; 12) were the most abundant families. Peltogyne gracilipes Ducke (Leguminosae), Pradosia surinamensis (Eyma) T.D.Penn. (Sapotaceae) and Ecclinusa guianensis Eyma (Sapotaceae) were the species with the highest importance value index (~ 25%). The dominance (m2 ha-1) of these species corresponds to > 36% of the total value observed in the forest inventory. Our dataset provides complementary floristic and structure information on tree and palm in Maracá, improving our knowledge of this Amazonian ecotone forest.

Volatile monoterpene 'fingerprints' of resinous Protium tree species in the Amazon rainforest.

Volatile terpenoid resins represent a diverse group of plant defense chemicals involved in defense against herbivory, abiotic stress, and communication. However, their composition in tropical forests remains poorly characterized. As a part of tree identification, the 'smell' of damaged trunks is widely used, but is highly subjective. Here, we analyzed trunk volatile monoterpene emissions from 15 species of the genus Protium in the central Amazon. By normalizing the abundances of 28 monoterpenes, 9 monoterpene 'fingerprint' patterns emerged, characterized by a distinct dominant monoterpene. While 4 of the 'fingerprint' patterns were composed of multiple species, 5 were composed of a single species. Moreover, among individuals of the same species, 6 species had a single 'fingerprint' pattern, while 9 species had two or more 'fingerprint' patterns among individuals. A comparison of 'fingerprints' between 2015 and 2017 from 15 individuals generally showed excellent agreement, demonstrating a strong dependence on species identity, but not time of collection. The results are consistent with a previous study that found multiple divergent copies of monoterpene synthase enzymes in Protium. We conclude that the monoterpene 'fingerprint' database has important implications for constraining Protium species identification and phylogenetic relationships and enhancing understanding of physiological and ecological functions of resins and their potential commercial applications.

Structure and tree species composition in different habitats of savanna used by indigenous people in the Northern Brazilian Amazon.

BACKGROUND: Woody plant diversity from the Amazonian savannas has been poorly quantified. In order to improve the knowledge on wood plants of these regional ecosystems, a tree inventory was carried out in four different habitats used by indigenous people living in the savanna areas of the Northern Brazilian Amazon. The habitats were divided into two types (or groups) of vegetation formations: forest (riparian forest, forest island, and buritizal = Mauritia palm formation) and non-forest (typical savanna). The inventory was carried out in two hectares established in the Darora Indigenous Community region, north of the state of Roraima. NEW INFORMATION: The typical savanna is the most densely populated area (709 stems ha-1); however, it has the lowest tree species richness (nine species, seven families) in relation to typical forest habitats: riparian forest (22 species, 13 families and 202 stems ha-1), forest islands (13 species, 10 families and 264 stems ha-1), and buritizal (19 species, 15 families and 600 stems ha-1). The tree structure (density and dominance) of the forest habitats located in the savanna areas studied in this work is smaller in relation to forest habitats derived from continuous areas of other parts of the Amazon. These environments are derived from Paleoclimatic fragmentation, and are currently affected by the impact of intensive use of natural resources as timberselective logging and some land conversion for agriculture.

Angiospermas em remanescentes de floresta montana no sul da Bahia, Brasil / Angiosperms of Montane Forest areas in southern Bahia, Brazil

Foi realizado um levantamento florístico de três remanescentes de floresta montana localizados na Mata Atlântica do sul da Bahia. Durante os anos de 2004 a 2008 foram feitas coletas periódicas de material botânico, principalmente ao longo de trilhas no interior dos fragmentos das áreas: Reserva Serra da Pedra Lascada - SPL, Reserva Serra das Lontras - SLO e Reserva Particular do Patrimônio Natural Serra Bonita - SBO. A riqueza florística em cada área foi comparada entre si e com outras áreas de Mata Atlântica na Bahia e no Sudeste do Brasil. Foi registrado um total de 1.129 espécies em 467 gêneros e 124 famílias. O hábito arbóreo representou 46,9 por cento das espécies, seguido de herbáceas (20,1 por cento), epífitas (19,5 por cento) e trepadeiras (13,5 por cento). As famílias Araceae, Asteraceae, Bromeliaceae, Fabaceae, Lauraceae, Melastomataceae, Myrtaceae, Orchidaceae, Piperaceae, Poaceae, Rubiaceae e Solanaceae apresentaram a maior riqueza florística nas três áreas em conjunto. O gênero Psychotria (Rubiaceae) apresentou o maior número de espécies em todas as áreas (21 spp.), destacando-se também Miconia (20 spp.), Solanum (20 spp.), Piper (19 spp.), Ocotea (16 spp.), Leandra (16 spp.), Peperomia (15 spp.) e Myrcia (14 spp.). Os resultados confirmam a elevada riqueza de angiospermas no sul da Bahia e evidenciam, pela primeira vez, a ocorrência de espécies características de regiões montanhosas da Mata Atlântica do Sudeste do Brasil nessa região.

A floristic study of three areas of montane Atlantic forest in southern Bahia, Brazil, was carried out. From 2004 to 2008 regular botanical collections were made, principally along trails in the interior of the forest fragments at: the Reserva Serra da Pedra Lascada (SPL), the Reserva Serra das Lontras (SLO) and the Reserva Particular do Patrimônio Natural Serra Bonita (SBO). The species richness of each area was compared to that of the other two, and together to other areas of Atlantic coastal forest in Bahia and southeastern Brazil. For all three areas, a total of 1129 species in 467 genera and 124 families were found. Trees represented 46.9 percent of the species, followed by herbs (20.1 percent), epiphytes (19.5 percent), and vines and lianas (13.5 percent). The families Araceae, Asteraceae, Bromeliaceae, Fabaceae, Lauraceae, Melastomataceae, Myrtaceae, Orchidaceae, Piperaceae, Poaceae, Rubiaceae, and Solanaceae showed the highest species richness for the three areas together. The genus Psychotria (Rubiaceae) had the highest number of species for all three areas (21 spp.), followed by Miconia (20 spp.), Solanum (20 spp.), Piper (19 spp.), Ocotea (16 spp.), Leandra (16 spp.), Peperomia (15 spp.), and Myrcia (14 spp.). The results confirm the high species diversity of angiosperms in southern Bahia and demonstrate for the first time the presence of species characteristic of montane regions of southeastern Brazil in this region.