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Reforestation with native species determines that autochthonous populations and plantations are often within the reach of gene flow. To address efficient strategies for forest plantation management it is fundamental to track the origin of reforestation material, in order to limit potentially detrimental effects on the adaptive potential of autochthonous populations. The use of genetic information to determine the origin of plantations is very effective when historical data about reforestation programs are absent. The main objectives of our study were to assess the origin of silver fir plantations in the Majella National Park (Central Apennines) and to compare genetic diversity parameters between plantations and natural stands. The latter objective is particularly relevant to evaluate the levels of genetic variation in plantations of local origin and to evaluate their suitability as already established reforestation stands. A comprehensive genetic dataset (1619 individuals from 33 natural silver fir populations genotyped at 16 nuclear microsatellite markers) was built to characterize potential seed sources for 10 plantations from the Majella National Park. Their genetic origin was assessed through combining the results of Bayesian assignment tests and analyses of genetic differentiation. Based on the genetic structure characterizing natural populations, we were able to definitely assess the origin of most of the planted individuals. Five plantations were established using material which most likely originated in natural populations that are only 10–20 km distant. These plantations harbour levels of genetic variation similar to the surrounding natural populations and are, therefore, to be considered valuable local forest genetic resources. The other five plantations consist either partially or entirely of allochthonous individuals which are similar to Alpine and northern Apennine populations. To avoid exotic gene flow to nearby autochthonous populations, we suggest the removal of plantations in which allochthonous individuals are present before they reach sexual maturity. However, before taking such action, we recommend the monitoring of the relative performance of different provenances, i.e. plantations entirely made by either putatively autochthonous or undoubtedly allochthonous material. Such an investigation would allow a thorough ex post evaluation of past reforestation programs. To conclude, our results show that genetic data can provide essential information for general decision-making in forest plantations management and, considering the thorough characterization of silver fir genetic structure in this multi-refugial area, such information can be particularly useful for a correct management of Apennine plantations. [ABSTRACT FROM AUTHOR]

Knowledge of the impact of forest management practices is crucial to allow the use of natural resources while ensuring the sustainability of genetic variation, which is essential for the potential adaptive capacity of forests. The main objective of this work was to study the effects of a seed cut on the genetic diversity of a mixed Nothofagus forest in northwestern Andean Patagonia. Silviculture based on the shelterwood system was carried out in stands composed of Nothofagus dombeyi , Nothofagus nervosa and Nothofagus obliqua , located in Lanín Natural Reserve (Neuquén province, Argentina). Through intensive sampling of pre (mature trees) and post (regeneration) harvest populations of all three species from a 3-ha plot established after 20 years of the silvicultural intervention, in combination with microsatellite genotyping (more than 2000 individuals with 15 markers), we determined that modification of relative abundance of species in the post-harvest population that followed the implemented management had altered the global genetic diversity of the mixed forest; however, no impact was detected at species level in the entire plot or in two subplots with different species proportions. Pollen and seed dispersal from the surrounding areas may have contributed significantly to maintaining both genetic diversity in the post-harvest natural regeneration and the low differentiation between this and the pre-harvest gene pool in all species. The use of species-specific markers allowed us to determine that the level of introgressive hybridization was not changed by management; however, further studies are required to evaluate whether this practice influences the directionality of introgression. [ABSTRACT FROM AUTHOR]

The current distribution of forest genetic resources on Earth is the result of a combination of natural processes and human actions. Over time, tree populations have become adapted to their habitats including the local ecological disturbances they face. As the planet enters a phase of human-induced climate change of unprecedented speed and magnitude, however, previously locally-adapted populations are rendered less suitable for new conditions, and ‘natural’ biotic and abiotic disturbances are taken outside their historic distribution, frequency and intensity ranges. Tree populations rely on phenotypic plasticity to survive in extant locations, on genetic adaptation to modify their local phenotypic optimum or on migration to new suitable environmental conditions. The rate of required change, however, may outpace the ability to respond, and tree species and populations may become locally extinct after specific, but as yet unknown and unquantified, tipping points are reached. Here, we review the importance of forest genetic resources as a source of evolutionary potential for adaptation to changes in climate and other ecological factors. We particularly consider climate-related responses in the context of linkages to disturbances such as pests, diseases and fire, and associated feedback loops. The importance of management strategies to conserve evolutionary potential is emphasised and recommendations for policy-makers are provided. [ABSTRACT FROM AUTHOR]

Abstract: The influence of forest management on stand structure and genetic diversity was studied in a European beech (Fagus sylvatica L.) forest in the Gran Sasso – Laga National Park, Apennine Mountains, central Italy. Field work was carried out in two plots to compare both spatial structure and genetic variability between an old-growth beech stand and a post-harvest naturally regenerated stand. The study was based on a total census of living trees within the plots. Vertical and horizontal stand structures were analyzed by means of spatial functions. Individuals were genotyped with four highly polymorphic nuclear microsatellite loci (nSSRs) and with RAPD markers. Population spatial genetic structure was inferred using a Bayesian Monte Carlo Markov Chains method implemented in the Geneland software. The major structural differences distinguishing the old-growth stand from the managed stand were tree size differentiation, vertical crown distribution and horizontal stem distribution. Concerning genetic features, the managed stand presented no significant differences from the unmanaged stand. Nevertheless, the old growth forest had a higher spatial structuring of genetic diversity than did the managed stand. Molecular markers (nSSR alleles and RAPD fragments) detected in the unmanaged stand were rarely detected in the managed stand, and rare markers were lost. [Copyright &y& Elsevier]

Pinus pinaster is a conifer native to western Europe and northern Africa. Following on-going breeding programmes, provenance and progeny trials were established in some of the countries of the species’ range (France, Portugal and Spain) and quantitative traits were measured: growth, stem form, survival and pest and disease resistance, amongst others. Populations from the wide range of P. pinaster were recently screened with molecular markers in order to assess their genetic diversity. Data were obtained using allozymes, chloroplast (cpSSRs) and nuclear (nuSSRs) microsatellites and amplified fragment length polymorphisms (AFLPs). Based on mtDNA-RFLP analysis, three maternal lineages (named “western”, “eastern” and “Moroccan”) were identified and no population showed a mixed composition. In this study, the imprint that differentiation in putatively isolated glacial refugia (identified by the different maternal lineages) might have left on the nuclear genome was analysed using a wide range of molecular markers and adaptive traits. Multivariate ordination of populations based on nuclear molecular markers (allozymes and nuSSRs) showed a clear clustering of provenances sharing a given mtDNA lineage. However, that clustering was found to be less tight when only quantitative traits were investigated. In P. pinaster, the within-population estimates of gene diversity using different traits were not correlated. Therefore, caution is advisable when designing conservation strategies based on molecular marker studies or a limited number of populations. After these results, we recommend a conservation strategy characterised by gene flow consistent with the current population structure, careful seed transfer among maternal lineages (if any), selection of populations for conservation based on the originality of their allelic composition and definition of Management Units (MUs) based on adaptive traits. [Copyright &y& Elsevier]