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International audienceAbstractKey messageThese results present great interest for the knowledge of fire effects and the regeneration capacity of the ecosystems, which is essential to minimise the long-term fire impacts.ContextThis study integrates thermal analysis of soil with tests of fire effects on Pinus radiata seeds germination and field seedling emergence in P. radiata plantations. The consequences of fire intensity P. radiata plantation regeneration can be predicted from the results.AimsThis study aims to identify the effects of fire on soil organic matter and emergence of P. radiata seedlings in a stand in NW Spain and to test the response of seeds from two provenances of P. radiata to smoke and heat.MethodsBurnt, unburnt and laboratory-heated samples of dry soil were analysed in a differential scanning calorimeter. Based on the comparison between heat released during the combustion of the organic matter of these samples, we estimated the fire severity. Early emergence of P. radiata seedlings was recorded in the field after fire. Finally, the effects of fire on seeds germination were tested in the laboratory.ResultsThe limited loss of soil organic matter indicated that the fire had been of low severity and that the temperatures reached during the fire remained below the ignition temperatures of soil organic matter. The germination rate was high in controls and the lowest fire severities but decreased with fire intensity. The two provenances differed in their response to fire intensity. Seedling emergence was moderate and varied over time.ConclusionThe intensity of the investigated fire remained moderate, with a limited loss of soil organic matter. It limited seedling germination and emergence. Nevertheless, despite the scarce seedling emergence observed in the field, re-establishment of the population was possible

& 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.

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