Understanding biological characteristics of Acacia melanoxylon in relation to fire to implement control measurements

Abstract

Acacia melanoxylon produces abundant seeds leading to large seed banks in the soil. These seeds display a large viability and their germination is stimulated by heat. To control the populations, it is necessary to remove adults and young individuals, and to prevent seedling establishment after fire occupying the space with rapid growth and high competitive native species. Acacia melanoxylon displays a widespread distribution in South West Europe, and an improved knowledge of its reproductive characteristics is required in order to control its expansion. This experiment was designed to provide useful indicators for an efficient management of A. melanoxylon populations based on its biological cycle in relation to fire. We explored the reproductive biology of A. melanoxylon, from seed dissemination—–quantifying seed rain over a year, their germination with and without fire—the seedling and sapling banks and the structure of the adult population. We analysed the effects of fire, seed maturation and scarification on the viability of seeds and the stimulation of seed germination in the aerial seed bank and in the different strata of the soil seed bank. Our results indicate that A. melanoxylon produced millions of seeds per ha and per year, half of which germinated and the other half went to the soil seed bank, maintaining the viability many years. The germination was the most critical step in the population dynamics of this species, and fire stimulates germination up to 90%. A. melanoxylon adults and seedlings removal, followed by colonization of rapid growth and high competitive native species that cover the ground very quickly would be a good control action.