Effect of high temperatures on seed germination and seedling survival in three pine species (Pinus pinaster, P. sylvestris and P. nigra)

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Abstract
In the present study, we analyse the germination and seedling growth of three Pinus species (P. pinaster, P. sylvestris and P. nigra) under laboratory conditions after thermal shocks simulating the temperature effects of fire. Temperatures up to 150°C and 5 min exposure show negative effects on the percentage germination of P. pinaster seeds. P. sylvestris and P. nigra cannot stand temperatures greater than 110°C and 5 min exposure. In all three species, thermal shocks delay the start of germination. In addition, seeds from P. pinaster germinate over a longer time range. Seedling aerial growth after germination is influenced by high temperatures in P. sylvestris and P. nigra, but not in P. pinaster. Finally, thermal shocks produce a reduction in root growth in comparison with aerial growth in P. sylvestris.