Effects of post-fire management practices and slope-aspect on medium-term Spanish black pine regeneration: implications of using a direct seeding strategy in burnt areas

The natural regeneration of non-serotinous Spanish black pine (Pinus nigra Arn. ssp. salzmannii) is known to be null or limited after severe wildfires. However, it remains challenging to define efficient management strategies within the burnt area, which can help to increase the post-fire resilience of this species. We conducted a direct seeding experiment during 2011-2015 to assess the effect of different post-fire management treatments (control, soil ripping, woodchips, and soil ripping + woodchips) performed in opposite slope-aspects (north- and south-facing) on pine emergence, seed predation, survival, growth, and biomass allocation during the early stages of seedling development (1-5 years) after a severe wildfire. Our results showed that the slope-aspect did not have an important effect in both the seedling emergence and seed predation rates. In contrast, the influence of slope-aspect was significant as both survival and growth of pine seedlings were reduced at the south-facing slope-aspect compared to the north-facing slope-aspect due to harsher environmental conditions. A variable and reduced impact on seedling emergence and seed predation rates was induced by both soil ripping and woodchips treatments. Overall, post-fire management treatments helped to enhance survival rates during early growth stages, although this effect was short-lasting. This knowledge can be used to define post-fire seeding management strategies oriented to enhance the resilience of severely burnt pine forest stands; therefore, while both the soil ripping and woodchips treatments might not be practices leading to increase their post-fire regeneration, direct seeding at north-facing slope-aspects could be a more appropriate management strategy.