Modelling Pinus pinaster seedling emergence and early survival after group selection system cuttings

Structural and species diversification of forests is essential for their adaptation to climate change. Planted forests normally present pure, even-aged structures, less resilient to disturbances and climate change, in which diversification efforts are especially needed. Managing these plantations through regeneration cuttings oriented to generate more diverse stands in terms of structure and species is a suitable option to explore. Hence, to assess whether group selection system cuttings can facilitate regeneration and diversification in Pinus pinaster stands, an experiment was established in a 70-year-old planted stand in southern Spain. The experiment involved the creation of 14 gaps with diameters ranging from 2 to 3.5 times the dominant height of the stand (36 – 62 m). Since 2018, ecological factors and seedling characteristics have been monitored annually every fall in 350 plots distributed within the gaps, in order to analyze their relationship with emergence and early survival of pine seedlings. Our results showed that inter-species competition and distance to the gap edge are negatively influencing seedling emergence. However, those competing shrubs are also facilitating seedling survival once they have developed juvenile needles. The thickness of the litter layer exhibited a negative role in seedling survival, as it impeded root access to the mineral soil. Although annually pine seedling emergence would allow the stand to successfully regenerate, we found a bottleneck in early survival that is hampering forest regeneration of the stand. Our results suggest the need to consider light availability/evapotranspiration relationships after regeneration cuttings in maritime pine stands, especially under climate change conditions. • Gap cutting is allowing gradual incorporation of pine seedlings. • Shrub and herbs are controlling maritime pine emergence and early establishment. • Our results emphasized the need for site-specific management under climate change.