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Avaliação da evolução da vegetação nos telhados verdes da ETAR de Alcântara : contribuição para promover a conectividade ecológica em meio urbano
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As coberturas verdes são uma solução de base natural. Enquanto tal, em contexto urbano, podem
promover diversos serviços de ecossistema, que impactam à escala do edifício, urbana e ecológica. Deste
modo a importância da vegetação numa cobertura verde estende-se além do seu valor estético. As suas
características funcionais influenciam os processos ecológicos, e consequentemente a performance da
cobertura verde no fornecimento de serviços de ecossistema. O presente trabalho foi desenvolvido
na cobertura verde da Fábrica de Água de Alcântara, em Lisboa. Esta cobertura intensiva, organizada
em talhões monoculturais, foi instalada em 2011, tendo como principais objetivos a integração
paisagística, a regulação térmica do edifício, o isolamento acústico e a atenuação de cheias. No entanto,
tendo uma localização privilegiada junto ao Parque Florestal de Monsanto, tem um enorme potencial
enquanto corredor ecológico. O objetivo do trabalho foi o de avaliar o estado e a evolução da vegetação
da cobertura verde após 10 anos da sua instalação, bem como encontrar soluções para a renovação do
coberto vegetal. Especificamente, envolveu: i) a caracterização do estado atual da vegetação da
cobertura; ii) a avaliação da evolução da composição da cobertura desde a sua implementação em 2011;
iii) a seleção de espécies de plantas autóctones para tornar o coberto vegetal mais sustentável e resiliente;
iv) a realização de um teste piloto em pequena escala para avaliar o desempenho de algumas das espécies
nativas selecionadas, a curto prazo. Observou-se a presença de 42 espécies, a larga maioria exótica,
cobrindo no seu conjunto apenas 38% da área total da cobertura verde. Das espécies presentes na
cobertura, destacaram-se duas gramíneas exóticas, por serem as espécies com maior extensão de área
ocupada, correspondendo a 19%. Observou-se ainda a presença de espécies nativas, presumindo-se que
terão ocorrido de forma espontânea, demonstrando o potencial da cobertura na conectividade ecológica.
No âmbito da renovação do coberto vegetal, desenvolveu-se uma metodologia, baseada numa
abordagem ecológica, para a seleção de espécies autóctones, caracterizando as espécies quanto a
características de adaptabilidade, funcionais e estéticas. Esta metodologia aplicou-se a um conjunto de
espécies nativas produzidas em viveiro comercial, tendo-se selecionado 30 espécies com potencial de
estabelecimento na cobertura, de acordo com as características mencionadas. Após a seleção das
espécies, procedeu-se à realização de um teste piloto, com um subconjunto das espécies selecionadas,
avaliando-se a sua sobrevivência e crescimento no contexto da cobertura verde da FA de Alcântara. Os
resultados demonstraram uma taxa de sobrevivência geral de 75%, tendo todas as espécies alcançado
uma taxa de sobrevivência acima de 50%. Na taxa de crescimento verificou-se uma grande variabilidade
de valores, devido em grande medida ao facto de as espécies terem alturas iniciais e máximas potenciais
diferentes e por serem características de diferentes estádios sucessionais da vegetação. Posteriormente,
compararam-se as características funcionais entre as dez espécies dominantes da cobertura verde e as
dez espécies do teste piloto demonstrando-se, com esta análise, que as espécies nativas selecionadas
poderão dar um contributo maior para a conectividade ecológica da cobertura verde da FA de Alcântara
com os espaços verdes na envolvente. Os resultados deste trabalho mostram que a gestão e manutenção
da vegetação têm um impacto importante na composição da cobertura verde, nomeadamente o corte
periódico e gestão da rega. Como tal, a sua adequação aos objetivos da cobertura verde é um aspeto
essencial para o seu sucesso e sustentabilidade. A progressiva substituição de espécies de plantas
exóticas, algumas com comprovado carácter invasor, por espécies nativas, apresenta-se como uma
solução viável para tornar as coberturas verdes urbanas mais ecológicas, pela sua maior adaptação ao
contexto biológico e climático local, e pelo seu contributo para a conectividade ecológica urbana com
potencial de promoção da biodiversidade, mantendo simultaneamente elevado valor estético.
Green roofs are a natural based solution. In the urban context, they can promote different ecosystem services, at the building, urban and ecological scales. The vegetation's importance in a green roof extends beyond its aesthetic value. Its functional traits influence ecological processes and the performance of the green roof in providing ecosystem services. The present study took place on the wastewater treatment plant's green roof in Alcântara, Lisbon. This intensive green roof, organized in monocultural plots, was installed in 2011, with the main objectives of landscape integration, building's thermal regulation, acoustic insulation, and flood mitigation. It has a privileged location, next to the Monsanto Forest Park, having an enormous potential as an ecological corridor. The objective of this study was to evaluate the green roof's vegetation condition and evolution ten years after installation, as well as to find solutions for the renewal of the plant community. Specifically, it involved: i) characterization of the current state of the plant community; ii) evaluation of the evolution of the community’s composition since its implementation in 2011; iii) the selection of native plant species to make vegetation cover more sustainable and resilient; iv) conducting a small-scale pilot test to assess the short-term performance of some of the selected native species. The presence of 42 species was observed, most of them exotic, covering 38% of the total green roof area. Two exotic grass' species stood out, as they occupied 19% of the total green roof area. The native species present may have occurred spontaneously, demonstrating the green roof's potential for ecological connectivity. For the vegetation's renewal, a new methodology was developed, based on an ecological approach, to select native species, considering their aesthetic, functional and adaptability characteristics. The methodology was applied to a set of native species produced in a commercial nursery, from which 30 species with potential for establishment in the green roof were selected. After the species selection, a pilot test was carried out, with a subset of those species, to evaluate their survival and growth in the context of the green roof . The results demonstrated a general survival rate of 75%, with all species reaching a survival rate above 50%. The growth rate showed high variability mainly because species had different initial and maximum potential heights and are characteristic of different successional stages of the vegetation. Subsequently, relevant functional traits were compared between the ten dominant species of the green roof and the ten species of the pilot test. This analysis demonstrated that the pilot test's species might contribute more to the ecological connectivity of the wastewater treatment plant's green roof with the surrounding green spaces. The results showed that the management and maintenance of vegetation, for example, periodic cutting, and abundant irrigation, had an impact on the composition of the green roof. As such, they should be adapted to the green roof objectives to ensure its success and sustainability. The progressive replacement of exotic plant species, some with a proven invasive character, by native species, proved to be a viable solution to make urban green roofs more ecological, due to their adaptation to the local biological and climatic context, and contribution to the urban ecological connectivity with the potential to promote biodiversity, while maintaining a high aesthetic value.
Green roofs are a natural based solution. In the urban context, they can promote different ecosystem services, at the building, urban and ecological scales. The vegetation's importance in a green roof extends beyond its aesthetic value. Its functional traits influence ecological processes and the performance of the green roof in providing ecosystem services. The present study took place on the wastewater treatment plant's green roof in Alcântara, Lisbon. This intensive green roof, organized in monocultural plots, was installed in 2011, with the main objectives of landscape integration, building's thermal regulation, acoustic insulation, and flood mitigation. It has a privileged location, next to the Monsanto Forest Park, having an enormous potential as an ecological corridor. The objective of this study was to evaluate the green roof's vegetation condition and evolution ten years after installation, as well as to find solutions for the renewal of the plant community. Specifically, it involved: i) characterization of the current state of the plant community; ii) evaluation of the evolution of the community’s composition since its implementation in 2011; iii) the selection of native plant species to make vegetation cover more sustainable and resilient; iv) conducting a small-scale pilot test to assess the short-term performance of some of the selected native species. The presence of 42 species was observed, most of them exotic, covering 38% of the total green roof area. Two exotic grass' species stood out, as they occupied 19% of the total green roof area. The native species present may have occurred spontaneously, demonstrating the green roof's potential for ecological connectivity. For the vegetation's renewal, a new methodology was developed, based on an ecological approach, to select native species, considering their aesthetic, functional and adaptability characteristics. The methodology was applied to a set of native species produced in a commercial nursery, from which 30 species with potential for establishment in the green roof were selected. After the species selection, a pilot test was carried out, with a subset of those species, to evaluate their survival and growth in the context of the green roof . The results demonstrated a general survival rate of 75%, with all species reaching a survival rate above 50%. The growth rate showed high variability mainly because species had different initial and maximum potential heights and are characteristic of different successional stages of the vegetation. Subsequently, relevant functional traits were compared between the ten dominant species of the green roof and the ten species of the pilot test. This analysis demonstrated that the pilot test's species might contribute more to the ecological connectivity of the wastewater treatment plant's green roof with the surrounding green spaces. The results showed that the management and maintenance of vegetation, for example, periodic cutting, and abundant irrigation, had an impact on the composition of the green roof. As such, they should be adapted to the green roof objectives to ensure its success and sustainability. The progressive replacement of exotic plant species, some with a proven invasive character, by native species, proved to be a viable solution to make urban green roofs more ecological, due to their adaptation to the local biological and climatic context, and contribution to the urban ecological connectivity with the potential to promote biodiversity, while maintaining a high aesthetic value.
Descrição
Relatório de Estágio de Mestrado, Ecologia e Gestão Ambiental, 2022, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Coberturas Verdes Serviços de Ecossistema Adaptabilidade Características funcionais Espécies nativas Teses de mestrado - 2022