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Litter production in forest ecosystems is a major indicator of primary productivity because litter helps incorporate carbon and nutrients from plants into the soil and is directly involved in plant-soil interactions. To our knowledge, few studies have investigated the relationship between species diversity and ecosystem processes in subtropical forest fragments. In this work, we determined forest structural parameters and assessed seasonal leaf litter input, leaf decomposition rate, litter quality and soil characteristics in two subtropical Atlantic Forest fragments. Litter production was greater in the native fragment with the higher species diversity (FN1). Th e two native fragments (FN1 and FN2) diff ered in basal area, volume and dominance in the upper stratum, which were positively correlated with litter production in FN1 but negatively correlated in FN2. Soil in FN1 exhibited higher contents of organic C, available phosphorus and exchangeable calcium, and the leaf litter had a higher C:N ratio. Although these results are consistent with a plant-soil feedback, which suggests the presence of a complementary eff ect, the dominance of certain families in subtropical forest fragments results in a selection eff ect on litter productivity and decomposition.

QuestionsCarbon dynamics in tropical forests is influenced by a variety of biotic and abiotic factors that act over temporal and spatial scales. At the local scale, carbon stock and dynamics can be determined by the environment and ecosystem diversity. Also, during forest regeneration, which is a temporal process, it is expected that those factors that influence carbon also change over time. Here we examine how carbon stock and dynamics are influenced by forest age, environment and functional diversity during forest regeneration. Using the relative effects of the different drivers of carbon dynamics, we attempt to discern the mechanisms (mass effect or niche complementarity) that explain those processes.LocationWe carried out this study in Atlantic Forest of different ages during natural regeneration in southern Brazil.MethodsWe measured environmental characteristics (soil physical and chemical attributes and canopy openness), estimated functional diversity and above‐ground carbon and its dynamics over time. We examined univariate and multivariate predictors of carbon stock and dynamics using structural equation models.ResultsWe found that age had the strongest influence on carbon stock, while environmental characteristics, functional and taxonomic diversities were much less important or unimportant. Our results suggest that the influence of time on tropical forest carbon dynamics overlaps and outweighs the effects due to environmental limits and mechanisms mediated by diversity (mass effects, niche complementarity).ConclusionsNatural regeneration can be an effective strategy for restoring carbon sequestration and methods that use manipulation of regenerating forests with the hope of improving the process are unlikely to bring additional advantage in terms of carbon sequestration.

RESUMO -O banco e chuva de sementes podem ser indicadores utilizados para avaliar o potencial de recuperação de uma área que sofre influência antrópica. Assim, os objetivos deste trabalho foram quantificar o número de sementes viáveis e estimar a diversidade de espécies do banco e chuva de sementes, a fim de conhecer o potencial de recuperação de uma área inserida em uma matriz agrícola. Foram instalados 40 coletores para avaliar a chuva de sementes, bem como coletadas amostras de solo, para caracterizar o banco de sementes. Na chuva de sementes, foram encontradas 2.079 sementes, pertencentes a 43 espécies, sendo as famílias Lauraceae e Fabaceae as mais representativas. No banco de sementes, germinaram 69 indivíduos pertencentes a 23 espécies, sendo a família Asteraceae a mais representativa. Observou-se elevada diversidade de espécies na chuva de sementes (H'= 2,34 nats ind -1 ), em que as sementes das espécies secundárias tardias foram as mais abundantes, enquanto no banco de sementes, as espécies pioneiras. Em conclusão, o fragmento florestal encontrava-se em estágio sucessional avançado, o que pode garantir estabilidade ao sistema diante da influência antrópica.Palavras-chave: Matriz agrícola; Estratégia de regeneração; Propágulos. SEED BANK AND SEED RAIN IN A TRANSITIONAL FOREST AREA IN THE SOUTH OF BRAZILABSTRACT -The seed bank and seed rain can be used as indicators to evaluate the recovery potential of an anthropic area. Our aims were quantify the number of viable seeds and estimate species diversity of bank and seed rain to assess the recovery potential of an area surrounded by agriculture. We installed 40 collectors to evaluate seed rain and collected soil samples for seed bank quantifications. We found 2,079 seeds in seed rain, comprising 43 species, being Lauraceae and Fabaceae the most abundant families. Seed bank was represented by 69 seeds of 23 species, predominating Asteraceae family. We observed high species diversity in seed rain (H'= 2.34 nats ind -1 ). Secondary species predominated in seed rain, while pioneer species in seed bank. In conclusion, forested area is in an advanced successional stage indicating a potential capacity of system under anthropogenic pressures.

Flood events in riparian forests of southern Brazil, can be characterized as unpredictable and of low magnitude with an average duration of less than 15 days. Inga marginata is an evergreen tree which grows in Southeast South America on a wide range of environments, including riparian forests. In this paper, the interactive effects of the light environment and soil flooding on morphological parameters of I. marginata were examined. Seedlings were acclimated in two contrasting light conditions: sun or shade for 30 days. Sun and shade plants were subjected to soil flooding for two periods; five or 15 days. After 5 days, the interaction between flooding and light did not affect growth, chlorophyll content and dry mass or the root-shoot ratio. After 15 days, flooded plants from the sunny treatment had a lower shoot dry mass compared to control sun plants and flooded plants from the shaded treatment. Moreover, the higher dry mass observed for shade plants compared to sun plants, following flooding, can also be directly associated with a higher content of soluble sugars. Shade plants of I. marginata showed a greater acclimation to soil waterlogging. This acclimation appears to be associated with a larger accumulation of soluble sugars compared to non-flooded plants. The responses observed on the shade plants appear to be decisive to indicate the use of I. marginata in degraded areas.Keywords: waterlogging, acclimation, plant dry mass, reforestation, riparian forests. Respostas de crescimento e acúmulo de açúcares solúveis em Inga marginataWilld. (Fabaceae) submetida ao alagamento e sob condições contrastantes de luminosidade ResumoAs inundações em florestas ripárias do Sul do Brasil, podem ser caracterizadas como imprevisíveis e de baixa magnitude com uma duração média de menos de 15 dias. Inga marginata é uma árvore que cresce no sudeste da América do Sul em uma grande variedade de ambientes, incluindo matas ciliares. Neste trabalho, os efeitos combinados da luminosidade e do e alagamento do solo nos parâmetros morfológicos de I. marginata foram examinados. As plântulas foram aclimatadas em duas condições contrastantes de luminosidade: sol e sombra por 30 dias. Plantas de sol e sombra foram submetidas ao alagamento do solo por dois períodos; cinco ou 15 dias. Após 5 dias, a interação entre a inundação e luminosidade não afetou o crescimento, teor de clorofila e massa seca e a razão raiz-parte aérea. Após 15 dias, plantas de sol sob inundação apresentaram menor massa seca na parte aérea em relação as plantas controle de sol e as plantas alagadas de sombra. Além disso, a maior massa seca observada nas plantas de sombra em comparação com plantas de sol, sob inundação, pode ser diretamente associado com um maior teor de açúcares solúveis. Plantas de sombra de I. marginata mostraram uma maior aclimatação ao encharcamento do solo. Esta aclimatação parece estar associada com um maior acúmulo de açúcares solúveis em comparação com as plantas não-inundadas. As respostas observadas nas plantas de sombra parecem ser det...