Importance of seed bank for the management of invasive Acacia dealbata

• Autor(a) principal: Passos, Isabel Maria Melo Mendes
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10773/13375
• topic: Ecologia; Sementes - Armazenamento; Acacia dealbata

The management of invasive plants is a hard task, which may be further hampered by the existence of extensive and long-lived seed banks. Acacia dealbata is an Australian tree considered one of the most aggressive invasive plant species in Portugal; the species is known to produce a persistent seed bank, but its extension and viability hasn’t been explored. In this work we aim to characterize the seed bank of A. dealbata, namely its extension, germinability and viability, in order to contribute to the management of the species, but also increase knowledge about its ecology. The extension of the seed bank was assessed by collecting soil samples in invaded stands and adjacent areas and counting the seeds. These were then germinated at 25ºC and some were exposed to an initial temperature of 60ºC, aiming to assess the effect of extreme soil temperature in dormancy breaking. Results showed that beneath canopy the seed bank averaged 4 608 seed/m2 (± 820), but maximum values can reach 62 747 seeds/m2. In areas adjacent to the invaded stands a mean value of 9 seeds/m2 (± 5) was found, with maximum values of 632 seeds/m2. Although only 8,6% of the seeds germinated without any stimulus, in total 89,7% of the seeds found showed to be viable after scarification, with 81% of the seeds remaining dormant in the soil. Of the seeds exposed to 60ºC almost 64% germinated without any physical stimulation, suggesting that extreme soil temperatures, reached in hot days, may break seed dormancy. Multivariate analysis showed that the probability of accumulating high numbers of seeds in soil decreases with higher stoniness and root density, and increases with higher A. dealbata density and with fewer fire events. Our results show that the soil seed bank of A. dealbata is numerous and viable, suggesting that risk of reinvasion after plant removal is very high. It was also shown that the species has the ability to disperse seed beyond invaded stands Although frequently disregarded, this study alerts for the need to include extensive and long-lived seed banks in the management of invasive plants, since these hidden legacies may quickly hamper control efforts. Alternatives to deal with such seed banks are discussed.