Overcoming lag phase: do regenerative attributes onset Acacia dealbata spread in a newly invaded system?

Abstract

Ecological theory predicts that the success of exotic plants in new environments depends on a combination of ecological attributes. Requirements for germination and seedling traits are the main components in the regenerative niche, and largely determine the success of exotic species in a new environment. Acacia dealbata Link is an Australian species with a great invasive potential. In Chaco Mountains (central Argentina), it seems to be undergoing a lag phase, as some local dominance in the form of dense monospecific patches has been recorded, although restricted to few disperse populations. In the present study we assessed which functional traits would allow this global invader to successfully overcome its lag phase, and what conditions could benefit or limit this process. Imbibition and germination experiments were designed, and included four temperature regimes in light and in continuous darkness. Additionally, germination response to light quality and simulation fire experiment was also conducted. Further, soil samples were taken to determine the size of the soil seed bank, and a morpho-functional characterisation of seedlings was conducted. Despite the absence of a consistent fire-stimulated germination response, our findings were in line with generalist germination requirements. Physical seed dormancy, large seed bank, broad temperature and light germination requirements, and fast-growing seedlings make this species a potential invader in this mountain system, and suggest that these regenerative attributes might help A. dealbata to overcome its present lag phase. Findings show that the efficiency of management decreases and the related economic cost increases as the time since invasion increases, so early intervention will be key in preventing spread of this species thorough this mountain region.