ABSTRACT Our research focused on the reproductive phenology of Mauritiella armata, a key veredas species in southeastern Brazil, and aspects of its floral and fruit morphology and sexual system. We observed the reproductive phenological patterns of M. armata for 36 months, and examined the relationships between phenophases and environmental variables to describe its phenological patterns in relation to environmental filters, as well as its floral and fruit morphologies, sexual system (to evaluate dioecy), and the biometry of its reproductive parts. Flowering was observed in the dry season and at the beginning of the rainy season, with fruiting occurring during the rainy season. The reproductive phenophases responded to environmental seasonality, principally temperature in the period immediately preceding the expression of the phenophase, as well as to environmental variations that had occurred up to six months earlier. The dioecious sexual system of M. armata was confirmed, with flowering synchronization between the sexes. The population studied did not exhibit apomixis, having xenogamy as its reproductive system. The staminate inflorescences were larger than the pistillate inflorescences and had greater numbers of flowers, although the pistillate flowers were larger. Wind pollen dispersal was not observed, thereby indicating that this species requires biotic pollination for fruit production.

Abstract Many factors can influence the structures and distributions of plant communities. Plant diversity of swamp forests reflect responses to water stress conditions. We evaluated the floristic diversity, structure, and composition of the regenerating shrub-tree species of six swamp forests in veredas ecosystems (northern Minas Gerais, Brazil), and the floristic similarities between them. All individuals ≥ 1 cm in diameter at ground level and < 3 cm in diameter at breast height were sampled in one hundred 25 m2 plots in each area. A total of 5442 individuals were recorded, distributed among 134 species, 85 genera, and 47 botanical families, with a diversity (Shannon) of 3.38 and equability (Pielou) of 0.69. Beta diversity was high, while similarities between the areas were low, with only two species common to all six sites. The forests showed different compositions, diversities, and natural regeneration structures, reflecting their ecotone nature and past anthropic impacts.

Resumo Este estudo analisou as variações florísticas, estruturais e suas relações com variáveis do solo em dois trechos de vegetação ripária em uma região ecotonal entre savana e zonas semi-áridas. Propomos a hipótese de que, apesar da proximidade entre as áreas amostradas, as condições do solo são distintas e levam a mudanças na estrutura e composição da vegetação, mas essas mudanças também são influenciadas pelo caráter ecotonal. Este estudo foi desenvolvido na APA do rio Pandeiros, Minas Gerais, onde alocamos 140 parcelas de 10 ×10 m (100 m2), com 10 m de distância entre parcelas, em duas áreas de vegetação ripária denominadas Larga e São Domingos (70 parcelas em cada área), onde realizamos o levantamento fitossociológico e coletamos amostras de solo. No total, 751 indivíduos arbóreos foram amostrados, distribuídos em 89 espécies e 35 famílias botânicas. As áreas diferiram fortemente na estrutura e composição das espécies, e apresentaram peculiaridades florísticas e influência da vegetação circundante. Apesar da baixa distância entre as áreas amostradas, estes são ambientes singulares influenciados por diferentes solos, pela composição mista da área ecotonal e os impactos antropogênicos a que estão expostas.

Abstract This study analyzed the floristic, structural variations and their relationships with soil variables in two stretches of riparian vegetation in an ecotonal region between savanna and semiarid zones. We following the hypothesis of despite the proximity between the sampled areas, soil conditions are distinct and lead to changes in structure and composition of the vegetation. This study was development at EPA of Pandeiros River, Minas Gerais, where we allocated 140 plots of 10 × 10 m (100 m2), with 10 m distance between plots, in two areas of riparian vegetation, named Larga and São Domingos (70 plots in each area), where we conducted the phytosociological survey and collected soil samples. In total, 751 arboreal individuals were sampled, distributed in 89 species and 35 botanical families. The areas differed strongly in structure and species composition, and showed floristic peculiarities and influence of surrounding vegetation. Despite of low distance between the sampled areas, these are singular environments influenced by different soils, by the mixed composition of the ecotonal area and the anthropogenic impacts to which they are exposed.

RESUMO As veredas são um tipo de vegetação associada aos cursos d'água, caracterizada pela presença da palmeira arbórea Mauritia flexuosa. Estes sistemas não são bem compreendidos e sofrem grande pressão antrópica. Os objetivos deste estudo foram descrever a regeneração natural de duas florestas higrófilas em sistemas de veredas com diferentes impactos antropogênicos e investigar se a variação nesta comunidade de plantas está associada as condições edáficas. O estudo foi realizado em sítios preservado e impactado localizado na área de Proteção Ambiental do rio Pandeiros, norte de Minas Gerais. Em cada sítio, 100 parcelas de 25 m2 foram estabelecidas para o levantamento dos arbustos e árvores regenerantes (≥1 cm de diâmetro na base do caule e < 3 cm de diâmetro na altura do peito). A estrutura da vegetação foi avaliada pelos parâmetros fitossociológicos, índice de similaridade e distribuição de tamanhos dos indivíduos. O estrato regenerativo correlacionou com as análises químicas e físicas do solo. A vegetação no sítio preservado foi caracterizada por um maior número de indivíduos e menor diversidade, mas continha espécies típicas de ambientes alagados. Os resultados também mostraram diferenças na disponibilidade de nutrientes do solo entre os sítios que influenciaram a distribuição de espécies nas duas áreas estudadas.

ABSTRACT Veredas (palm swamps) is a type of vegetation associated with watercourses, characterized by the presence of Mauritia flexuosa palm trees. These systems are not well understood and suffer from high anthropogenic pressure. The aims of this study were to describe the natural regeneration of two swamp forests in vereda systems with different anthropogenic impacts and investigate if the variation in these plant communities are associated to edaphic conditions. The study was performed in preserved and impacted sites located in the Environmental Protection Area of the Pandeiros River in northern Minas Gerais. At each site, one hundred 25 m2 plots were established for surveying regenerating shrubs and trees (≥1 cm diameter at the base of the stem and < 3 cm diameter at breast height). Vegetation structure was evaluated by phytosociological parameters, similarity index, and size distribution of individuals. Regenerating strata was correlated with chemical and physical soil analyses. The vegetation at the preserved site was characterized by a higher number of individuals and a lower diversity but contained species that were typical of flooded areas. The results also showed differences in soil nutrient availability between sites that influenced the distribution of species at the two study sites.