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

Abstract

& Key message 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. & Context 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. & Aims 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. & Methods 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. & Results 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%. & Conclusion 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.

Fire Severity Drives the Natural Regeneration of Cytisus scoparius L. (Link) and Salix atrocinerea Brot. Communities and the Germinative Behaviour of These Species

“…Scarified seeds of C. scoparius were subjected to a solution of 2,3,3-triphenyl tetrazolium chloride salt at 1%. Five replicates, of 25 seeds each, were made [29,38]. The seeds were kept in the solution for 48 h in the dark and then all tincted seeds were recorded as live seeds.…”

“…Fire severity, through combustion or lethal heating during burning, directly determines the availability of post-fire in situ propagules generated [90]; however, it can also lead to greater recruitment of seedlings and resprouts [12,38] and, likely, this affects the natural regeneration of communities. Our results showed that the germination behaviour of C. scoparius and S. atrocinerea were strongly influenced by certain fire factors.…”

Fire and seed maturity drive the viability, dormancy, and germination of two invasive species: Acacia longifolia (Andrews) Willd. and Acacia mearnsii De Wild

“…Fire and summer temperatures work together breaking seed dormancy (Luna 2020), opening the possibility for new species to establish in natural communities or even become dominant. Since germination is the most critical stage in the life cycle of many plants, the influence of fire on seed dormancy breaking and germination may be decisive for the establishment of native (Reyes et al 2000) and invasive alien species (IAS) (Arán et al 2017). The ecological advantage of the non-dormant phase is that seeds can germinate abundantly in favorable conditions and establish large populations quickly.…”

“…Seed maturation can interact with fire and/or with summer temperatures (Luna 2020) by modulating the dormancy and germination response to fire (Reyes and Casal 2001;Ooi 2010). Specifically, Arán et al (2017) found that 2-year-old Acacia melanoxylon R. Br. seeds slightly increased germination compared with fresh seeds and that the seeds of the soil bank (many years of maturation) were mainly dormant seeds whose germination was stimulated by high fire temperatures, and García-Duro et al (2019) found great modifications of the viability, dormancy, and germination of Paraserianthes lophanta (Willd.)…”

“…Particularly, heat shocks generated during fires are reported to have an important role releasing seed dormancy of Acacia species (Arán et al 2013;Ooi et al 2014;Cruz et al 2017). Seeds from Australian Acacia seed banks are generally 85% viable (Milton 1980;Arán et al 2017) and may remain dormant for 50 years or more (Holmes 1989;Leino and Edqvist 2010). Since fire may eliminate native seeds from the surface layer, stimulation of germination of seeds from soil seed bank by fire could cause a massive germination event of acacias.…”