Summary Soil nutrient availability can strongly affect root traits. In tropical forests, phosphorus (P) is often considered the main limiting nutrient for plants. However, support for the P paradigm is limited, and N and cations might also control tropical forests functioning. We used a large‐scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low‐fertility soils in Central Amazonia after 1 yr of fertilisation. Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition. Here we showed that rock‐derived nutrients determined root functioning in low‐fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicated that even slow‐growing tropical rainforests can respond rapidly to changes in resource availability.

No abstract

No 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.

Invasive species can affect ecosystems functioning by forming dense monospecific stands and outcompeting native plants. However, the performance of the invader depends on its plastic responses to abiotic attributes of invaded communities. Understanding the interplay between intraspecific competition and environmental conditions is important to elucidate the domain and aggressive potential of invasive species. Here, we assessed the performance of the invasive Hedychium coronarium in two levels of intraspecific competition created through rhizome density under full light and partial shade. We tested the influence of light, density and their interaction on ramet length and number of ramets during the first three months after planting (phase 1) and after 22 months (phase 2), and on rhizome dry weight and the ramet/rhizome biomass ratio in phase 2. In both phases, ramets were longer under shade and the number of ramets was higher under low rhizome density indicating lower intraspecific competition. In phase 2, there was a negative effect of rhizome density on ramet length, but it was restricted to shade, probably due to the aggravation of competition for light. Rhizome dry weight was greater under shade conditions and it was not affected by rhizome density, and ramet/rhizome ratio did not differ between treatments. Our results supported a large phenotypic plasticity of H. coronarium ramets, which allowed similar performances despite variations in environmental conditions and population densities. We suggest that this mechanism of energy allocation enhances the success of this invasive plant in varied habitats, such as open and closed, forested sites.

efluente. O sistema de tratamento proposto foi eficiente na remoção de E. coli da água, sendo que, após estabilização do sistema, ocorreu remoção média de 95% da contaminação. A etapa contendo E. crassipes apresentou maior remoção média, porém mostrou diminuição da eficiência a partir de 60 dias após implementação do sistema. A remoção média das etapas contendo C. demersum e T. domingensis foi prejudicada devido à presença de E. coli no solo usado como substrato durante as primeiras semanas de experimento. Contudo Typha domingensis).The most probable number of E. coli in the water was quantified for supply site, effluent and at each stage of treatment (sedimentation and use of each type of aquatic macrophyte). We conclude that E. coli contamination in water supply and in fishpond can reach the environment through the effluent. The proposed treatment system was efficient in removing E. coli from the water, and when the system was stabilized the average removal efficiency of E. coli was 95%.The tank containing E. crassipes showed the highest removal average, even though it exhibited an efficiency reduction after 60 days of experiment.The average removal of the tanks containing C. demersum and T. domingensis was hampered due to the presence of E. coli in soil used as substrate. However, after the decrease of substrate contamination effect, these two plants were essential for the maintenance of water quality of the treated effluent, indicating the benefits of aquatic macrophytes diversity in treatment systems. The effluent quality was maintained even when some system steps presented a decrease of removal efficiency.

No abstract

Diante das alterações ambientais, em consequência das práticas antrópicas, é necessário desenvolver novas mentalidades que busquem caminhos para reduzir as pressões humanas na degradação ambiental. O artigo tem como objetivo apresentar caminhos trilhados em trabalhos de pesquisa em Educação Ambiental não formal. Para tanto, foi realizado um levantamento dos principais conceitos abordados e métodos utilizados nos artigos apresentados na comunicação oral do Grupo de Discussão de Pesquisa (GDP) em contextos não escolares, no X Encontro de Pesquisa em Educação Ambiental (EPEA), em 2019. Dos artigos avaliados, foram reconhecidas três categorias de conceitos: pertencimento, relação sociedade-natureza e o próprio conceito de educação ambiental; e duas categorias de método: oito artigos trabalharam a pesquisa com atividades formativas, e dez buscaram compreender o contexto e as opiniões dos participantes. Tais caminhos sinalizam uma postura de respeito à pluralidade de saberes e de manifestações, compatíveis com a pluralidade do mundo, na busca de concretizar  uma educação ambiental dialógica, acessível, democrática, diversa, cidadã, política e crítica.