ABSTRACT
The native bracken (Pteridium arachnoideum) often occurs in mono-specific stands in the Brazilian Cerrado, and this dominance can impact on both the above-ground vegetation and soil seed bank. This study investigated how invasion by this species over a 20-year period changed the seed bank and the relationship between the seed bank and litter mass. We extracted soil samples from three replicated invaded and uninvaded sites, and followed seedling emergence for six months. We collected the above-ground biomass and litter of P. arachnoideum in ten 1m2 plots from three invaded sites. There was no difference between invaded and uninvaded areas in seed bank richness, diversity or overall abundance. The most abundant family was the Melastomataceae, followed by the Poaceae. The Melastomataceae was more abundant in uninvaded sites, but the most common species of this family (Tibouchinastenocarpa) was not affected. The grasses were more common in invaded sites in the rainy season and were affected by heterogeneity in the litter layer. The seed bank could play a role in the recovery of these invaded areas, but the presence of weeds and invasive grasses could constrain their use as a management strategy.
Subject(s)
Biodiversity , Plants , Pteridium/physiology , Seeds/physiology , Brazil , Seasons , SoilABSTRACT
Abstract The native bracken (Pteridium arachnoideum) often occurs in mono-specific stands in the Brazilian Cerrado, and this dominance can impact on both the above-ground vegetation and soil seed bank. This study investigated how invasion by this species over a 20-year period changed the seed bank and the relationship between the seed bank and litter mass. We extracted soil samples from three replicated invaded and uninvaded sites, and followed seedling emergence for six months. We collected the above-ground biomass and litter of P. arachnoideum in ten 1m2 plots from three invaded sites. There was no difference between invaded and uninvaded areas in seed bank richness, diversity or overall abundance. The most abundant family was the Melastomataceae, followed by the Poaceae. The Melastomataceae was more abundant in uninvaded sites, but the most common species of this family (Tibouchinastenocarpa) was not affected. The grasses were more common in invaded sites in the rainy season and were affected by heterogeneity in the litter layer. The seed bank could play a role in the recovery of these invaded areas, but the presence of weeds and invasive grasses could constrain their use as a management strategy.
Resumo O samambaião (Pteridium arachnoideum) frequentemente domina áreas de cerrado, e pode alterar tanto a vegetação estabelecida quanto o banco de sementes do solo. Nesse estudo investigamos como áreas de cerrado invadidas por essa espécie a mais de 20 anos alteraram o banco de sementes, e também a relação entre banco de sementes e quantidade de serapilheira. Extraímos amostras de solo em três invadidas e em áreas controle adjacentes, e monitoramos a emergência de plântulas por seis meses. Coletamos a biomassa aérea e a serapilheira de P. arachnoideum em dez parcelas de 1m2 nas áreas invadidas. Ariqueza, diversidade e abundância totalnão diferiram entre áreas invadidas e controle. A família mais abundante foi Melastomataceae, seguida por Poaceae. Melastomataceae foi mais comum em áreas controle, mas não a espécie mais comum nessa família (Tibouchina stenocarpa). Gramíneas foram predominantes em áreas invadidas durante a estação chuvosa, e foram afetadas pela heterogeneidade da camada de serapilheira. O banco de sementes pode ser importante para a recuperação dessas áreas invadidas, mas esse uso pode ser prejudicado pela presença de ervas daninhas e gramíneas invasoras.
Subject(s)
Biodiversity , Plants , Pteridium/physiology , Seeds/physiology , Brazil , Seasons , SoilABSTRACT
Pteridium is a cosmopolitan genus that acts as an invasive species in many parts of the world. Most research on this genus has occurred in Europe, and there is a lack of data on it from South America, in spite of causing considerable conservation problems. We compared the biomass allocation of P. esculentum subsp. arachnoideum in two ecosystems in Brazil - Atlantic forest and Brazilian savanna. We measured the biomass of fronds, rhizomes and above-ground litter. We also compared the density, length and biomass of fronds from this Brazilian study with similar data of P. esculentum subsp. arachnoideum derived from Venezuela and P. aquilinum from Europe. P. esculentum subsp. arachnoideum showed a wide response range. We found a negative relationship between frond and necromass, indicating a negative feedback effect, while a positive relationship was observed between frond and rhizome biomass. The continental comparison of relationships showed that Pteridium responds in a different way in both Brazil and Europe, and that in Brazil fronds tend to be longer and heavier, presumably as a result of the continuous growing season in South America while is shortened in Europe by frost. The paper shows the ability of Pteridium to adapt to different ecosystems.
