Estrutura, composição florística e relações ambientais da regeneração natural em uma floresta estacional semidecidual

This paper aims to evaluate the floristic and structure of natural regeneration in a forest fragment located in the south of Espírito Santo State, as well as to verify the interaction between vegetation and environmental variables. The study was developed in Private Reserve of Nature Patrimony (RPPN) Cafundó, with twelve sample units (1 x 20m), where three classes based on size - Class 1 (plants between 0.1 and 1m high), Class 2 (plants between 1.1 and 3m high) and Class 3 (plants higher than 3m and less than 5cm DBH). This RPPN has a total area of 517ha, which approximately 358ha were used for allocation of experimental units. Individuals were classified according to ecological group and dispersion syndrome. Floristic diversity, equability, density and frequency of species were also calculated. Analysis of natural regeneration, floristic similarity between natural regeneration and the upper layer as well the regenerating layer interaction with environmental variables was performed through Canonical Correspondence Analysis. We found 678 individuals distributed in 73 morphospecies/species, with Actinostemon klotzschii and Goniorrhachis marginata being the most abundant. Sorensen's similarity between natural regeneration and the adult tree layer was 29%. The most dominant ecological groups were late secondary, while zoochory was the predominant dispersion syndrome among existing species. Shannon diversity index was 3.13 and equability 0.72. Goniorrhachis marginata, Actinostemon klotzschii and Psychotria carthagenensis species had correlation with carbon (C), phosphorus (P), declivity and canopy cover. We concluded that the natural regeneration component within studied area has a high richness and density of individuals when compared to studies developed in similar phytophysiognomies. The studied environmental variables seem to have little influence on the distribution of natural regeneration species in the RPPN, once only carbon, phosphorus, declivity and canopy cover have explained the species distribution within fragment.O objetivo deste estudo foi descrever a florística e estrutura da regeneração natural do estrato arbustivo-arbóreo em um fragmento florestal no sul do estado do Espírito Santo, bem como verificar a interação da vegetação com algumas variáveis ambientais selecionadas. Foi desenvolvido na Reserva Particular do Patrimônio Natural (RPPN) Cafundó, em doze subparcelas de 1 x 20 m, onde foram delimitadas três classes de tamanho - classe 1 (plantas entre 0,1 e 1 m de altura), classe 2 (1,1 e 3 m de altura) e classe 3 (altura maior que 3 m e menor que 5 cm DAP). A RPPN possui uma área de 517 ha, onde 358 ha foram utilizados para alocação das unidades experimentais. Os indivíduos foram classificados quanto ao grupo ecológico e síndrome de dispersão. Foi calculado o índice de diversidade, equabilidade, densidade e frequência das espécies e a similaridade de Sorensen entre o estrato regenerante e adulto. A interação do estrato regenerante com variáveis ambientais foi realizada através da Análise de Correspondência Canônica. Foram amostrados 678 indivíduos, distribuídos em 73 espécies/morfoespécies, sendo Actinostemon klotzschii e Goniorrhachis marginata as mais abundantes. A similaridade entre regeneração e estrato arbóreo foi 29%. O grupo ecológico e a dispersão predominante, respectivamente, foram secundária tardia e zoocoria. A diversidade de Shannon (H’) foi 3,13 e equabilidade de 0,72. As espécies Goniorrhachis marginata, Actinostemon klotzschii e Psychotria carthagenensis tiveram correlação com carbono (C), fósforo (P), declividade e cobertura de dossel. Concluiu-se que a regeneração natural na área estudada possui elevada riqueza e densidade de indivíduos quando comparado a estudos desenvolvidos na mesma fitofisionomia. As variáveis ambientais estudadas parecem ter pouca influência na distribuição das espécies da regeneração natural, uma vez que apenas o carbono, o fósforo, a declividade e a cobertura do dossel explicaram parte da distribuição das espécies no fragmento

Interplays between Atta ants (Formicidae: Attini), soils and environmental properties in the Brazilian Neotropics: a preliminary assessment

Leaf-cutting ants are the most important herbivore in the neotropics, represent active agents of pedobioturbation, and are regarded as ecosystem engineers. These ants have a wide variety of ecological functions, such as pollination, seed dispersal, and tree-growing control. Despite this importance, little is known on their distribution in relation to possible soil and environmental conditions that affect Atta ants occurrence. This study aimed to spatialize the main occurrences of Atta species in the Brazilian territory and evaluate the main environmental conditions driving ants species in the Brazilian tropical landscapes, at a preliminary basis. We compiled data of occurrence for 12 Atta species from Global Biodiversity Information Facility (GBIF) databases, and scientific literature (up to 2019) for each Atta species. To each point, we obtained the respective geoenvironmental data as soil properties, biome, geology, vegetation land use, and climate variables. From these data, possible zonalities of occurrence of 9/10 Atta species were discussed. We applied the principal components analysis (PCA) and Canonical Correspondence Analysis (CCA) to identify the environmental gradient and investigate the possible interplay between variables and species. Soil, vegetation, and land use attributes are the main drivers on the distribution of Atta at local scale where their evolutionary physiological and foraging adaptations allow them to nest and maintain the fungi culture. At broader scales, climatic attributes are key drivers of Atta distribution across Brazil, and also influence pedogenic processes. Our study demonstrates that species of Atta ants are not randomly dispersed in Brazil and are strongly associated with complex and diverse Brazilian landscapes. We remark that further studies on the distribution of leaf-cutting ants of the Atta genus in Brazil, as well as their evolutionary phylogenetics, are needed, based on larger database