Resumo A dinâmica da serapilheira é um dos processos fundamentais para o crescimento e manutenção dos fragmentos florestais nativos, sendo considerada a principal via de ciclagem de nutrientes nas florestas. Portanto, estudos sobre a serapilheira acumulada e conteúdo de nutrientes subsidiam informações para uma melhor compreensão da dinâmica dos nutrientes. O objetivo do estudo foi avaliar o estoque de serapilheira e nutrientes em diferentes estações do ano e a taxa instantânea de decomposição em um fragmento de Floresta Atlântica ao longo de dois anos. A amostragem da serapilheira foi realizada em 12 parcelas permanentes com dimensões de 20 m x 50 m. Determinou-se a massa seca da serapilheira e o teor dos nutrientes. O acúmulo médio anual de serapilheira foi de 5.269 kg ha-1. Não houve diferença estatística na quantidade de serapilheira entre as estações do ano. Houve diferença estatística nos teores de N, P, K Ca e Mg entre as diferentes estações do ano. Os estoques de nutrientes foram de 123.3, 92.8, 13.2, 11.8, 9.6 e 3.0 kg ha-1 para Ca, N, Mg, S, K e P, respectivamente. O total de nutrientes na serapilheira acumulada foi de 253,7 kg ha-1 ano-1. O tempo de renovação da serapilheira foi de 281 dias. O tempo para a decomposição de 50% e 95% da mesma foi de 196 e 850 dias, respectivamente. A produção média de serapilheira, o estoque de nutrientes e a decomposição estão de acordo com outros estudos realizados, indicando que o fragmento de Floresta Atlântica sazonal semidecidual apresenta indicadores de ciclagem de nutrientes. Esses resultados encontrados mostram que o ecossistema se encontra sustentável sob ponto de vista da ciclagem e liberação dos nutrientes.

Abstract Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Therefore, studies on accumulated litter and nutrient content provide information for a better understanding of nutrient dynamics. The aim of the study was to evaluate leaf litter and nutrient stock in different seasons and the instantaneous rate of decomposition in an Atlantic Forest Fragment over two years. Litter sampling was carried out in 12 permanent plots with dimensions of 20 m x 50 m. Litter dry mass and nutrient concentration were determined. The average annual accumulation of litter was 5269 kg ha-1. There was no statistically significant difference in the amount of litter between seasons. There was a statistically significant difference in the contents of N, P, K Ca and Mg between the different seasons. Nutrient stocks were 123.3, 92.8, 13.2, 11.8, 9.6, 3.0 kg ha-1 year-1 for Ca, N, Mg, S, K and P respectively. The total of nutrients in the accumulated litter was 253.7 kg ha-1 year-1. The litter renewal time was 281 days. The times required for 50% and 95% litter decomposition were 196 and 850 days. The average litter stocks, nutrients and decomposition are in line with other studies, indicating that the Atlantic Forest fragment seasonal semi-deciduous presents indicators of nutrient cycling. These results show that the ecosystem is sustainable from the point of view of cycling and nutrient release.

Abstract The objective of this study was to analyse the initial medium-term growth of a P. reticulata settlement under different phosphorus doses. The experiment was carried out in an area of Atlantic Forest, Sooretama, Northern Espírito Santo State, Brazil. Five doses of P per each tree (0 g, 27 g, 47 g, 67 g and 87 g) were tested in a randomized block design with three replicates and 18 plants per plot. At 3 months, 9 months and 15 months, height and diameter were measured at the soil level. At 36 months height, diameter at breast height, survival, basal area, and nutritional evaluation of the trees were measured. A logistic model was also used to model the growth in height of individual trees and a logistic model considering fixed effects and mixed form (fixed and random effects), in order to verify if the inclusion of the random effect (tree) would result in gains in terms of accuracy in the estimation of the future height of P. reticulata trees. The species presents potential for use in reforestation programs under edaphoclimatic conditions tested and under similar conditions. The species was not very demanding in P, and the addition of this nutrient promotes negative effects on its growth in the short and medium term. Regarding the model of growth in height, the logistic model adjusted in the mixed form showed to be superior to the traditional adjustment.

Resumen El objetivo de este estudio fue analizar el crecimiento inicial a mediano plazo de un asentamiento de P. reticulata bajo diferentes dosis de fósforo. El experimento se llevó a cabo en un área del Bosque Atlántico, Sooretama, norte del estado de Espírito Santo, Brasil. Se probaron cinco dosis de P por árbol (0 g, 27 g, 47 g, 67 g y 87 g) en un diseño de bloques al azar con tres repeticiones y 18 plantas por parcela. A los 3 meses, 9 meses y 15 meses se midió la altura y el diámetro a nivel del suelo. A los 36 meses de la siembra, se midió el diámetro a la altura del pecho, la supervivencia y el área basal y se hizo una evaluación nutricional de los árboles. También se utilizó un modelo logístico para modelar el crecimiento en altura de árboles individuales y el modelo logístico considerando efectos fijos y forma mixta (efectos fijos y aleatorios) para verificar si la inclusión del efecto aleatorio (árbol) resultaría en ganancias en términos de precisión en la estimación de la altura futura de los árboles de P. reticulata. La especie presenta potencial para su uso en programas de reforestación en condiciones edafoclimáticas probadas y en condiciones similares. La especie no fue muy exigente en fósforo y la adición de este nutriente promovió efectos negativos en su crecimiento a corto y mediano plazo. Con respecto al modelo de crecimiento en altura, el modelo logístico ajustado en forma mixta mostró ser superior al ajuste tradicional.

ABSTRACT The development of tissue cultured-based protocols applied to braúna, an endangeres species, would be though highly desirable. However, contamination-free explants are determinant for the success of this technique, which might be vulnerable to the toxicity of disinfectants. Here, we aimed at establishing an efficient protocol for in vitro production of axenic seedlings of braúna and to evaluate the toxicity of disinfectant agents in the Lactuca sativa model species. Experiments I and II: Seeds were treated with sodium hypochlorite (NaOCl) and fungicide captan, with and without residue, by different immersion times, respectively. The following were analyzed: contamination; germination and normal and abnormal seedlings. Experiment III: Lettuce seeds placed in Petri dishes were exposed to 2.5 mL captan at 0.5; 1; 2; 4 and 8%; 0.01% glyphosate and distilled water. The germination, length of seedlings, cell cycle, nuclear and chromosomal alterations of the cells of the root meristem were assesed. The isolated use of NaOCl was not efficient in the disinfestation of braúna seeds. However, the immersion of the seeds in captan, for 10 minutes with its residue, led to higher germination and vigor indexes; however, resulted in the formation of abnormal seedlings. This compound exhibited toxicity in the lettuce model seeds because affected the germination and the whole development of the seedlings, showing clastogenic and aneugenic action in the meristematic cell cycle.