ABSTRACT The ability to maintain high competitiveness under a wide range of conditions is common among successful invasive species. The performance of rhizomatous macrophytes in different habitats is closely related to morphological and physiological adaptations in the rhizome system. We investigated the effects of soil moisture conditions on the microstructure of rhizomes of Hedychium coronarium (Zingiberaceae), an aggressive invader of Neotropical riparian sites. We collected rhizome fragments of H. coronarium and soil samples in wet and dry regions of riparian areas dominated by this species in southeastern Brazil. We measured soil moisture content gravimetrically and rhizome fragments were fixed, sectioned, and stained for histological analysis. Only rhizomes from wet regions exhibited aerenchyma, whereas amyloplasts were much more abundant and larger in rhizomes from dry regions than in rhizomes from wet regions. Even though low starch content in wet soils indicates the occurrence of anaerobic metabolism, the presence of aerenchyma may contribute to the typically high performance of H. coronarium in waterlogged soils. Although further studies are needed to assess how responses at the rhizome level affect the competitive ability of H. coronarium, our findings show that they may play a role in the dominance of this species in Neotropical riparian sites.

ABSTRACT Biological invasions have negative impacts on different ecosystem-level functions, such as nutrient cycling. In aquatic environments, exotic litter can change the activity of the decomposer microbiota. We tested whether litter quality, litter decay, and enzyme activity differed between nativeEgeria densaand exoticHydrilla verticillata. The invasive plant presented higher lignin and lower cellulose content than the native plant. Both species showed rapid fibre decay in the first five days.E. densahad higher cellulose and hemicellulose decay thanH. verticillatta. Although the species did not exhibit differences in enzyme activity over time,E. densahad a higher enzymatic efficiency thanH. verticillata. This differential enzymatic performance can cause changes in the mineralisation processes of the invaded environments. The lower decomposition rates for invasive litter, associated with differences in litter quality, could increase the amount of particulate organic material in invaded environments.

RESUMOVários artigos vêm mostrando que os sistemas de metrô causam impactos na qualidade do ar, através da emissão de material particulado. No entanto, não há informações disponíveis sobre o efeito desse impacto na vegetação. Folhas de árvores de três espécies diferentes localizadas do lado da saída de dutos de um metrô no Rio de Janeiro, Brasil, se mostraram mais assimétricas do que as de árvores localizadas do lado da entrada. Essas folhas também apresentaram alterações na camada de cera epicuticular e no conteúdo de clorofila.

ABSTRACTWhile a number of papers have shown that subway systems have an impact on the air quality through the release of particulate matters, no information about the impact of such particles on tree attributes is available. Tree leaves from three different species from the exit side of a subway station in Rio de Janeiro, Brazil, were more asymmetrical than leaves from the entrance side. This leaves also presenting changes in leaves cuticle and chlorophyll content.

Espécies invasoras podem causar alterações estruturais e funcionais nos ecossistemas invadidos, tais como alterações na cadeia trófica. Neste trabalho, descrevemos o primeiro registro de herbivoria de rametas de lírio-do-brejo, erva daninha aquática agressiva no Brasil, por capivaras em uma área de várzea de uma reserva de Cerrado. Este é o primeiro registro de herbivoria de rametas de H. coronarium em áreas invadidas. As capivaras desta região podem estar se utilizando dos bancos de lírio-do-brejo como habitat e como recurso alimentar, o que poderia ocasionar alterações na competição aparente entre esta invasora e as macrófitas nativas.

Invasive species can cause structural and functional changes in their non-native habitats, such as changes in the trophic chain. We describe ramet herbivory of butterfly ginger, an aggressive aquatic weed in Brazil, by capybaras in a floodplain area of a Cerrado reserve. This is the first record of herbivory of H. coronarium in invaded areas. Capybaras could be using the butterfly ginger as habitat and as a food resource, which could cause changes in apparent competition between these invasive and native macrophytes.

Este trabalho apresenta uma análise da climatologia de frentes frias e do regime de ventos induzido por esses fenômenos sobre a Região Metropolitana de São Paulo (RMSP), no período de 21 anos (1987 a 2007). Foram utilizados dados de vento da estação meteorológica do IAG/USP, localizada no bairro da Água Funda - São Paulo - SP. Os resultados mostram que três frentes, em média, chegam a RMSP mensalmente, sendo que sua freqüência é maior nos meses de março a maio, e de agosto a dezembro. Com relação ao vento, esse mostrou-se mais intenso nos dias anteriores a passagem da frente fria, mínimo na chegada, aumentando gradativamente nos dias seguintes (quando sua direção é predominantemente de sudeste (90% da velocidade média, e 70% das rajadas). As correlações feitas entre frentes frias e a dinâmica nos reservatórios mostraram que, em média, o tempo de resposta de um evento para outro foi de 2 a 3 dias na represa Guarapiranga, e 3 a 4 dias na represa Billings. Os parâmetros físico-químicos medidos nas represas foram temperatura (C), pH e Turbidez (NTU).

This study presents an analysis of climatology of cold fronts and wind regimes induced by these phenomena over the Metropolitan Region of São Paulo (MRSP) within a time period of 21 years from 1987 to 2007. The wind data series were acquired from the IAG/USP meteorological station, located at Água Funda neighborhood of São Paulo City. The results showed that three fronts, on average, reached the MRSP monthly, and their frequency is higher from March to May and from August to December. Winds showed to be more intense few days before the cold front passage. During the cold front arriving day, wind velocity was at lowest value, increasing gradually in the following days, when the direction was predominantly from southeast quadrant (90 % around the mean velocity and 70 % of the gusts). The correlations between the cold fronts and the dynamics of the reservoirs showed that, in average, the time lag between these events was 2 to 3 days for Guarapiranga Reservoir and 3 to 4 days for Billings Reservoir. The physical-chemical parameters measured in the reservoirs were temperature (C), pH and Turbidity (NTU).