RESUMEN
Understanding the plant communities affected by human activities related to urbanization is an important tool to conserve these. In this way, this study on an urban forest fragment aimed to evaluate, through a phytosociological study and investigation of the germination of the seed bank, the current forest structure, the successional strata, and the regenerative capacity of the remnant. Three different stages comprised this research, the first with a floristic survey of the entire forest remnant, then the phytosociological study of the canopy (PAP above 10 cm) and regeneration strata (PAP 5-10 cm), and at last, the study on the seed bank. The phytosociological survey of the canopy stratum presented 1,368 individuals, with 41 species distributed into 24 families. The stratum of natural regeneration had 665 individuals, being 38 species distributed into 24 families. The seed bank was made up by only 8 native species, and 3 exotic species. The floristic diversity of the seed bank in all samples was low due to few species provide seeds to the soil. In addition, the strata and the seed bank had a low similarity, confirming thus the fragility and the need for preservationist attitudes.
Understanding the plant communities affected by human activities related to urbanization is an important tool to conserve these. In this way, this study on an urban forest fragment aimed to evaluate, through a phytosociological study and investigation of the germination of the seed bank, the current forest structure, the successional strata, and the regenerative capacity of the remnant. Three different stages comprised this research, the first with a floristic survey of the entire forest remnant, then the phytosociological study of the canopy (PAP above 10 cm) and regeneration strata (PAP 5-10 cm), and at last, the study on the seed bank. The phytosociological survey of the canopy stratum presented 1,368 individuals, with 41 species distributed into 24 families. The stratum of natural regeneration had 665 individuals, being 38 species distributed into 24 families. The seed bank was made up by only 8 native species, and 3 exotic species. The floristic diversity of the seed bank in all samples was low due to few species provide seeds to the soil. In addition, the strata and the seed bank had a low similarity, confirming thus the fragility and the need for preservationist attitudes.
Asunto(s)
Desarrollo de la Planta , Banco de Semillas , UrbanizaciónRESUMEN
Urban forests are usually isolated and highly disturbed, however they are important shelters for tolerant animal species. Their food habits expose the different ecological roles these animals perform in the habitat. We analyzed the contribution of Didelphis albiventris Lund (1840), as a seed disperser, to the vegetation renewal of an urban forest fragment, describing its frugivorous diet and testing the viability of ingested seeds. Both male and female of white-eared opossum included a vast variety of items in their diet, mainly invertebrates and fruits. Fruits were consumed during all year round and seasonality was not observed. The majority of consumed fruits was from pioneer plant species, which is common in disturbed areas, in accordance to the opossum's opportunistic habits. The viability of ingested seeds, evaluated by linear logistic regression models applied to data from germination tests, was different of the seeds collected directly from ripe fruits; it varied among species, maybe due to the intrinsic characteristics of plant species. As a highly generalist species, D. albiventris can inhabit disturbed environments and then disperse seeds from pioneer plants, where the vegetation must be restored. It is crucial that this process does not depend only on the specialist frugivores, which are frequently absent in urban forest fragments. Therefore, the presence of generalist species of secondary environments has its importance emphasized.
Florestas urbanas são geralmente isoladas e altamente degradadas; contudo são importantes abrigos para espécies de animais tolerantes. Os hábitos alimentares destes animais explicitam os diferentes papéis ecológicos que eles desempenham no hábitat. Nós analisamos a contribuição de Didelphis albiventris Lund (1840) como dispersor de sementes para a regeneração da vegetação de um fragmento florestal urbano. Para isso, descrevemos sua dieta frugívora e testamos a viabilidade das sementes por ele ingeridas. Tanto machos quanto fêmeas de gambá-de-orelha-branca incluiram uma grande variedade de itens alimentares na dieta, principalmente invertebrados e frutos. Frutos foram consumidos durante todo o ano e a sazonalidade não foi observada. A maioria das sementes defecadas era proveniente de plantas pioneiras, comuns em ambientes perturbados, o que concorda com seu hábito oportunista. A viabilidade das sementes ingeridas, verificada mediante modelos de regressão logística linear aplicada a dados de testes de germinação, foi diferente das sementes obtidas de frutos maduros e variou entre espécies, talvez devido a características intrínsecas da planta. Enquanto uma espécie generalista, D. albiventris é capaz de habitar ambientes perturbados, e dispersar as sementes de plantas de estágio inicial de sucessão, onde a vegetação necessita ser restaurada. É essencial que este processo não dependa exclusivamente de frugívoros especialistas, que na maioria das vezes estão ausentes nos fragmentos florestais urbanos. Consequentemente, a presença de espécies generalistas de ambientes secundários tem sua importância enfatizada.