Fernandes, P., Antunes, C., Pinho, P., Máguas, C. & Correia, O. (2016) Natural regeneration of Pinus pinaster and Eucalyptus globulus from plantation into adjacent natural habitats.Forest Ecology and Managment , 378, 91–102. DOI:10.1016/j.foreco.2016.07.027 (IF2016 3,064; Q1 Forestry)
The tree species used in planted forests are highly productive and have an important role in countries economy but the expansion of these trees into habitats outside plantations is a concern for managers and conservationists. Among the most planted forest species worldwide, we can find eucalypts and pines species. Understanding spatial patterns and the factors that influence these species colonization is crucial to increase the knowledge about expansion capability of these species and may help managers to improve and prioritize eventual control plans. Our study aimed to identify the recruitment spatial patterns of Pinus pinaster (native species) and Eucalyptus globulus (exotic species) into habitats surrounding plantations in Portugal (native forests, grasslands and shrublands) and to determine the factors that influence recruitment. This was done by looking at the recruitment success in several habitats near plantations, using a spatial gradient of distance to plantations edge. We observed as expected that the recruitment of P. pinaster and E. globulus decreased exponentially from the plantation edge. However, the higher P. pinaster seedling recruitment in this study (P. pinaster: 247 seedlings/ha; E. globulus: 22 seedlings/ha), the smallest decline in seedlings density with distance from plantation boundary (P. pinaster = −0.036 seedlings/m vs E. globulus = −0.048 seedlings/m), and the longer distance of seedling establishment, demonstrate clearly that P. pinaster is more successful colonizing the habitats near plantations than E. globulus. Nevertheless E. globulus can growth seedlings within the planted stands suggesting that the species is becoming naturalized. However, localized recruitment (92% of the total seedlings recorded were located less than 15 m from the plantation edge) and lower levels of establishment of E. globulus from managed plantations, suggested that this species did not demonstrate an invasive behavior. However, future research in abandoned eucalyptus plantation is needed to understand the role of plantation management and age as barriers to E. globulus colonization. Results from our survey revealed the suitability of all habitat types studied for P. pinaster natural regeneration, although their recruitment was more limited in forest habitat type. Forest and grassland were very resistant to E. globulus establishment. The two species recruitment was also influenced by different factors, with P. pinaster being independent of climatic variables, while E. globulus was affected by temperature seasonality and recruitment was found to be higher in areas with lower seasonal differences.