Variações espaço-temporais no estoque de sementes do solo na floresta amazônica

A dispersão eficiente, a longevidade e a capacidade das sementes de permanecer em estado latente a espera de condições adequadas de germinação no banco de sementes do solo da floresta garantem a presença de espécies arbóreas pioneiras nas áreas perturbadas. As variações estacionais e espaciais na densidade e na composição florística do banco de sementes em Florestas Tropicais Úmidas são assuntos ainda pouco compreendidos. Este trabalho verificou a existência de modificações espaço-temporais do banco de sementes presente em áreas de Floresta Tropical úmida localizadas próximas a Manaus, AM. Em cada uma das seis áreas estudadas, foram coletadas 40 amostras circulares de solo superficial (10 cm de diâmetro e 2 cm de profundidade) ao acaso. Essas amostras foram coletadas a cada dois meses, entre agosto/2004 e junho/2005,. As amostras de solo foram distribuídas em bandejas em casa de vegetação e a emergência das sementes presentes no solo foi acompanhada por 4 meses. Houve uma redução significativa (H: 14,09, p < 0,05) na densidade média de sementes no solo em junho (início da estação seca) em relação a fevereiro (meio da estação chuvosa). Houve também diferença significativa (H: 188,72, p < 0,05) na densidade média de sementes do solo presente nas diferentes áreas amostradas. Assim como para outras áreas de florestas tropicais, o banco de sementes permanente da floresta foi dominado por espécies pioneiras, principalmente da família Melastomataceae, enquanto as espécies típicas da Floresta Tropical madura foram raras no solo florestal

NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

Strong floristic distinctiveness across Neotropical successional forests

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained

Mecanismos de regeneração natural em diferentes ambientes de remanescente de Floresta Ombrófila Mista, São Francisco de Paula, RS Mechanisms of natural regeneration in different environments in the remaining Mixed Rain Forest, São Francisco de Paula, RS

O objetivo deste trabalho foi avaliar os mecanismos de regeneração natural em três agrupamentos florísticos em remanescente de Floresta Ombrófila Mista, localizado em São Francisco de Paula, RS. A coleta dos dados foi realizada em seis conglomerados de um hectare, subdivididos em 16 parcelas cada, nas quais foram coletadas amostras da chuva de sementes, do banco de sementes no solo e do banco de plântulas. Os grupos florísticos apresentaram diferenças significativas para a densidade de indivíduos na chuva de sementes e no banco de plântulas. Para o banco de sementes no solo, o grupo G1 diferiu dos grupos G2 e G3. A riqueza de espécies observada no banco de plântulas sugere que este pode ser o mecanismo principal de manutenção da diversidade no remanescente. A chuva de sementes foi abundante e representou uma fonte expressiva de propágulos para abastecer o banco de sementes e banco de plântulas local e das áreas circunvizinhas. O banco de sementes do solo não apresentou potencial florístico para representar a riqueza de espécies presentes na vegetação arbórea, corroborando o estágio sucessional avançado desta floresta, uma vez que o banco de sementes é formado principalmente de espécies pioneiras.<br>The aim of this study was to evaluate the natural regeneration mechanisms in three floristic groups of the remaining Mixed Rain Forest, located in San Francisco de Paula, RS. The data were collected in six conglomerates of one hectare, subdivided into 16 plots, in which seed rain, soil seed bank, and seedling bank were collected. The groups presented differences in the density of individuals in the seed rain and in the seedling banks. For the soil seed bank, the group G1 differed from the groups G2 and G3. The seedlings bank, due to the wealth of species, may be the primary mechanism for maintaining diversity in the remnant. Seed rain was abundant and represented an expressive source of seeds to supply the seed bank and the seedling bank site and surrounding areas. The seed bank of soil did not show potential to replace the floristic richness of species in the arboreal vegetation, confirming the advanced stage of forest succession, once the seed bank is composed mainly of pioneer specie

Morfologia de sementes e do desenvolvimento pós-seminal de espécies de Bromeliaceae Seed and post-seminal development morphology on Bromeliaceae species

O estudo teve como objetivos caracterizar as sementes, fornecendo informações sobre o tipo e o tempo médio de germinação e de formação de plântulas, além de descrever a morfologia do desenvolvimento pós-seminal de seis espécies de Bromeliaceae. Os resultados mostram germinação do tipo epígea e plântulas criptocotiledonares para todas as espécies. As porcentagens máximas de germinação obtidas, acima de 80%, indicam alta qualidade fisiológica das sementes. O tempo médio de germinação e de formação de plântulas foi de 4-15 e 8-18 dias, respectivamente. As sementes são filiformes a elípticas, lisas ou com apêndices plumosos. Os caracteres morfológicos mais relevantes para a diferenciação entre gêneros e subfamílias de Bromeliaceae referem-se à forma e ao tipo de apêndices das sementes, e na forma e tamanho da bainha cotiledonar, hipocótilo e raiz primária das plântulas, subsidiando estudos taxonômicos, ecológicos e na área de tecnologia de sementes.<br>The aim of this study was to characterize the seeds, providing information about germination type and seedling rate, in addition to describe the post-seminal development morphology of the six species of Bromeliaceae. The results showed that the germination is epigeal with cryptocotylar seedlings. Maximum germination percentage was over 80%, for all species, indicating high physiological quality of the seeds. Germination and seedling rate was 4-15 and 8-18 days, respectively. Seeds are filiform to elliptical, smooth or with flight apparatus. The most relevant morphological characters for distinguishing among genera and subfamilies are shape and appendices of the seeds, form and size of the cotyledonal sheath, hypocotyl and primary root, providing information on taxonomic, ecological and seed technology studies

Biodiversity recovery of Neotropical secondary forests

Unidad de excelencia María de Maeztu MdM-2015-0552Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes

Multidimensional tropical forest recovery

Tropical forests disappear rapidly because of deforestation, yet they have the potential to regrow naturally on abandoned lands. We analyze how 12 forest attributes recover during secondary succession and how their recovery is interrelated using 77 sites across the tropics. Tropical forests are highly resilient to low-intensity land use; after 20 years, forest attributes attain 78% (33 to 100%) of their old-growth values. Recovery to 90% of old-growth values is fastest for soil (12 decades). Network analysis shows three independent clusters of attribute recovery, related to structure, species diversity, and species composition. Secondary forests should be embraced as a low-cost, natural solution for ecosystem restoration, climate change mitigation, and biodiversity conservation