The development of studies on natural regeneration in fragments of the Atlantic Forest assists to evaluate the regenerative power of forests against natural and anthropic disturbances. So, the objective of the work was to analyze the structure of the regenerative component and ecological succession of arboreal species in an urban fragment of Atlantic Forest. The study was undertaken in Parque Estadual Dois Irmãos (PEDI), in Recife, Pernambuco, in which 10 subplots of 1 m x 25 m (25 m²) each was installed. As inclusion criterion, the regenerating individuals of arboreal species should have a height equal to or greater than one meter and circumference at the height of the chest (CAP 1.30 m) inferior to 15 cm. The individuals were classified as the ecological groups origin (native or exotic species) and were calculated via phytosociological parameters such as heights classes for regenerating individuals and diversity index. For data analysis Mata Nativa version 4.05 was used. The families that presented the highest number of species were: Myrtaceae and Fabaceae. It was observed that 15% of the species belong to the pioneer group, while 48% belonged to the initial secondary group, and 22% to the late secondary group. The distribution of individuals of the species Hirtella racemosa and Chamaecrista ensiformis in the different size and relative density classes allow us to affirm that these species act directly in the process of ecological succession. The fragment is in the initial secondary stage of succession.

Por meio da liberação de substâncias alelopáticas, produzidas no metabolismo secundário, um indivíduo pode influenciar o desenvolvimento de outros organismos em seu entorno. Esse trabalho teve como objetivo avaliar o efeito de extratos aquosos de partes de Tradescantia zebrina Heynh. ex Bosse. (zebrina) sobre a germinação de sementes de Lactuca sativa L. (alface). O experimento foi conduzido sob condições naturais do ambiente (25°C e 72% UR), utilizando extratos de folha e raiz de zebrina nas concentrações de 100%, 75%, 50% e 25%, com água destilada como tratamento controle. Foram utilizadas 50 sementes de alface, distribuídas uniformemente em papel germitest®, devidamente esterilizado e umedecido com a solução, em caixas gerbox®, com cinco repetições. As observações ocorreram por sete dias, avaliando-se porcentagem de germinação (%G), índice de velocidade de germinação (IVG), tempo médio de germinação (t) e velocidade média de germinação (v). Os dados foram submetidos às análises estatísticas observando-se, posteriormente, que as aplicações de extratos de folhas e das raízes de zebrina reduziram o percentual de germinação e a velocidade de germinação das sementes de alface, indicando o efeito alelopático.

This study aimed to evaluate the allelopathic effects of aqueous extracts of Tectona grandis L.F. in various concentrations produced from leaves and flowers. Seeds of lettuce (Lactuca sativa L.) and germitest paper as substrate were used, the germitest paper was moistened with distilled water, and aqueous extract in concentrations of 100%, 75%, 50%, 25% and 0% (distilled water). The extracts were homogeneously deposited on twenty-five seeds evenly distributed in gerbox-type boxes. The materials used in the experiment were previously sterilized with alcohol (70%). A completely randomized experimental design with four replicates was used and the experiment was conducted under natural conditions of temperature and humidity. The tests were carried out in the laboratory, the experiment was watched for 10 days always at the same hour and the variables analyzed were Germination Percentage (%G), Speed of Germination Index (SGI), Mean germination time (MGT) and Mean speed of germination (MSG). The data were submitted to Analysis of Variance and compared by Tukey test considering 95% of probability. It was observed that there were no significant differences in leaf and flower extracts for the variables %G, MGT and MSG, however, in SGI aqueous leaf extract differed significantly at the highest concentrations (75% and 100%). It was concluded that aqueous extracts of leaves and flowers of T. grandis had no inhibitory potential in relation to the percentage and average germination time of lettuce seeds at any of the concentrations.

Rainfall is the main source of water in forest ecosystems and stemflow is an important pathway for nutrients to enter these ecosystems. Thus, this study aimed to evaluate effective precipitation in a fragment of tropical forest and stemflow nutrient input of tree species in different periods of rainfall. Total precipitation and throughfall were measured using rain gauges inside and at the edge of the fragment. After a phytosociological survey, nine species with the highest absolute density in the fragment were chosen and three individuals were selected. Water collectors were fixed around their trunk to collect stemflow water. The stemflow water was measured in milliliters, and pH, electrical conductivity and the input of K, P and Na were determined. Based on the throughfall and stemflow, the effective precipitation was calculated. The stemflow nutrient input presented the following decreasing order: Na>K>P. The high input of Na can be explained by the fact that the fragment is close to the coastal area. Stemflow of forest species proved to be an important pathway for nutrients to enter forest ecosystems, effectively participating in nutrient cycling.