The impact of afforestation on vegetation, soil properties, and Pinus brutia Ten. recruitment in post-fire P. brutia forests

In post-fire environments, non-native species plantations can significantly affect community dynamics, including species composition, diversity, and ecosystem processes. Long-term studies are essential to assess stand invasiveness, the persistence of planted species, and the re-establishment of native species. This study examines Eucalyptus camaldulensis (River red gum), Pinus pinea (Stone pine), and Pinus brutia (Turkish red pine) plantations in post-fire P. brutia forests in Turkey by assessing the vegetation characteristics and soil properties, as well as the allelopathic effects of these species on the seed germination and seedling development of P. brutia. A total of 17 woody taxa were recorded across three types of plantation sites. The E. camaldulensis stand had the highest species richness (14 species), followed by the P. brutia and P. pinea stands (10 and 9 species, respectively). An 11-year monitoring study of tree canopy cover in plantation forests revealed that P. brutia successfully colonized and expanded its canopy cover within the E. camaldulensis stand. In contrast, P. brutia entered and later established in the P. pinea stand. Leaf extract and soil experiments to detect the potential allelopathic effects of E. camaldulensis and P. pinea indicated that, unlike the inhibitory effects observed in P. pinea, E. camaldulensis may promote P. brutia seed germination. Regarding soil properties, the E. camaldulensis stand showed higher cation exchange capacity, electrical conductivity, organic matter content, and nutrient availability than the other stands. In conclusion, our findings demonstrate that P. brutia has a high potential to re-colonize areas afforested with other species after a fire, and the time required for its re-colonization depends on the facilitating or inhibiting effect created by other species, the size of the plantation stand, and the distance to the P. brutia stands.