Multiple drivers influence tree species diversity and above-ground carbon stock in second-growth Atlantic forests: Implications for passive restoration.

Second-growth forests (SGF) are critical components for limiting biodiversity loss and climate change mitigation. However, these forests were established after anthropic disturbances such as land use for planting, and in highly human-modified landscapes. These interventions can decrease the ability of biological communities to recover naturally, and it is necessary to understand how multiple drivers, from local scale to landscape scale influence the diversity and carbon stock of these forests in natural regeneration. For this, we used data from 37 SGF growing on areas previously used for eucalyptus plantations in the Brazilian Atlantic Forest, after the last cut cycle. For each SGF, the forest tree species diversity was calculated based on the Hills number, and we also calculated the above-ground carbon stock. Then, we evaluated the influence of multiple environmental factors on these indexes: soil properties, past-management intensity, patch configuration, and landscape composition. Little influence of soil properties was found, only soil fertility negatively influenced above-ground carbon stock. However, past-management intensity negatively influenced tree species diversity and carbon stock. The isolation of other forests and tree species propagules source distance (>500 ha) also negatively influenced the diversity of species. This is probably due to the favoring of tree pioneer species in highly human-modified landscapes because they are more tolerant of environmental changes, less dependent on animal dispersal, and have low carbon stock capacity. Thus, areas with higher past-management intensity and more isolated areas are less effective for passive restoration and may require intervention to recover tree diversity and carbon stock in the Atlantic Forest. The approach, which had not yet been applied in the Atlantic Forest, brought similar results to that found in other forests, and serves as a theoretical basis for choosing priority areas for passive restoration in the biome.

Climate and evolutionary history define the phylogenetic diversity of vegetation types in the central region of South America.

In South America the biogeographic history has produced different biomes with different vegetation types and distinct floras. As these vegetation types may diverge in evolutionary histories, we analysed how alpha and beta phylogenetic diversity vary across them and determine the main drivers of variation in phylogenetic diversity. To this end, we compiled a list of 205 sites and 1222 tree species spread over four biomes and eight vegetation types in central South America. For each site we evaluated six measures of evolutionary alpha diversity (species richness, phylogenetic diversity sensu stricto and the standardized effect size of phylogenetic diversity, mean phylogenetic distance and mean nearest taxon distance) and beta diversity (phylogenetic Sorensen's similarity). We checked the influence of spatial and environmental variables using generalized least squares models. The greatest phylogenetic differentiation was found between west and east of central South America, mainly between the Chaco communities and the other vegetation types, suggesting that species found in this biome come from different lineages, comparing with the others vegetation types. Our results also showed a clustered phylogenetic structure for the Dry Chaco woodlands, which may be associated with harsh environmental conditions. In addition to historical process, climatic conditions are the main drivers shaping phylogenetic patterns among the distinct vegetation types. Understanding patterns of phylogenetic diversity and distribution can greatly improve conservation planning and management since it allows the conservation of unique biome characteristics.

Flooding avoidance Triplaris gardneriana Wedd. (Polygonaceae): growth and morpho-anatomical aspects / Evitação do alagamento em Triplaris gardneriana Wedd. (Polygonaceae): crescimento e aspectos morfo-anatômicos

The aim of this study was to analyze the effect of flooding in Triplaris gardneriana Wedd, cultivated in drained soil (control) and in flooded condition. The experiment was developed in a greenhouse, using plants with 90 days after the emergency. The response to treatment was evaluated at 0, 30, 60 and 90 days. Growth measurements were made, such as biomass allocation, relative growth rate (RGR). Adventitious roots were not measured only observed, as well as the development of hypertrophied lenticels. The RGR was continuously reduced along the 90 days in flooding conditions for the roots, stem and leaves, compared to control. The flooding of the substrate caused alterations such as: increasing of the cortex width and diameter of the central cylinder of root and increasing the diameter of the vessel element of the root and stem. Results show that T. gardneriana remains under stress when submitted to flooding. Therefore, the production of structures as lenticels, aerenchyma and adventitious roots, structures related to the avoidance of this type of stress, were key factors for the maintenance and survival of T. gardneriana.

O objetivo deste trabalho foi analisar o efeito do alagamento em Triplaris gardneriana Wedd, cultivadas em condições de solo drenado (controle) e solo alagado. O experimento foi desenvolvido em casa de vegetação, utilizando-se plantas com 90 dias após a emergência. As respostas ao tratamento foram avaliadas para os períodos de 0, 30, 60 e 90 dias. Foram feitas medidas de crescimento, como alocação de biomassa, taxa de crescimento relativo (TCR). Raízes adventícias não foram medidas, apenas observadas, assim como o desenvolvimento de lenticelas hipertrofiadas. A TCR foi continuamente reduzida durante os 90 dias em condições de inundação para as raízes, o caule e as folhas em relação ao controle. O alagamento do substrato provocou alterações anatômicas como aumento da largura do córtex e do diâmetro do cilindro central da raiz e aumento do diâmetro dos elementos de vaso do caule e da raiz. Nossos resultados indicam que T. gardneriana permanece em estresse quando submetida a inundações. No entanto, a produção de estruturas relacionadas à evitação deste tipo de estresse foi chave para a manutenção e sobrevivência de T. gardneriana.