Marginal/peripheral populations of forest tree species and their conservation status: report for southeastern Europe

The Southeastern Europe, which is usually known as Balkan Peninsula, harbours a vast number of plant species among which a great number of relict and endemic ones. This region was one of the main areas in Europe where plant species found shelter in refugia and survived during the last glaciation. These refugia were the source areas for the postglacial colonization of many forest tree species. Human impact has been reported in the region since antiquity resulting in fragmentation of forests and deforestation. Marginal/peripheral (MaP) populations could be identified for most of the forest tree species occurring in the region. However, detailed information about MaP populations is restricted to few cases. Most of the MaP populations identified by FP1202 experts are not located in protected areas. Thus, approximately 27 % of the MaP populations are included in Natura 2000 sites, and only one out of the four reported populations is included in a genetic conservation unit. Many MaP populations (40%) are registered as seed stands and only 14% are included in EUFGIS database. Conservation of forest genetic resources, including MaP populations, is a component of sustainable management of forests in many countries of the region

The Dynamics and Variability of Radial Growth in Provenance Trials of Norway Spruce (Picea abies (L.) Karst.) Within and Beyond the Hot Margins of its Natural Range

Multi-site field trials provide valuable data for the investigation of possible effects of environmental changes on forest tree species. We analyze the descendants of plus trees from 33 Norway spruce seed sources of Romanian Carpathians, at age 30, in four comparative field trials: two established in the natural range of species and two outside of it. The dynamics and variation of radial growth, earlywood and latewood were analyzed. The influence of populations, site conditions and climatic factors were also quantified. The provenances response in the four comparative trials was asymmetric for mean radial growth, but its dynamics was less favourable outside of the natural range. Analysis of variance showed significant differences (P<0.001) between the testing sites, but non-significant (P<0.05) for the populations. Populations x localities interaction was high (P<0.001) in the first half of the testing period, but decreased over time, becoming not significant at the age of 30. At intra-populational level, the average coefficient of variation for radial growth was higher outside the natural range, whereas the proportion of latewood decreased. The temperature in the first half of the growing season negatively influenced (P<0.001) the radial increment, but in the latewood proportion significat effects (PË‚0.05) were recorded only in trials located outside of the natural range. An increased variability of radial growth and a decrease of latewood proportion are expected in Norway spruce stands located at lower altitudes, towards the limits of the natural range. Our results may contribute to the sustainable management of Norway spruce forests within and outside its natural range

Bud burst and flowering phenology in a mixed oak forest from Eastern Romania

Bud burst and flowering phenology have been observed in year 2008 ina natural white oak species complex situated in eastern Romania. A total of 300 mature individuals was mapped and identified based on leaf morphology. The community consists of four oak species: Quercus pedunculiflora, Q. robur, Q. pubescens and Q. petraea. A set of 28 individuals could not be unambiguously classified to one or another species. Data on bud burst showed a normal distribution and the differences among species were small. The "very late" flushing was recorded on 15th of April, three weeks later when compared to early flushing individuals. The time period between the bud burst and the complete development of leaves was nearly the same in all oak species, varying on average, between 18.4 and 20.6 days. The spatialdistribution of phenological groups within the complex appears to be non-randomly, because in many parts of the study plot exist groups in which most of the trees belong to the same phenological category. Our results indicate an overlap in flowering time for all oak species which occur in the area. The data support the hypothesis that interspecific gene flow is possible between closely related oak species

Resilient forests for the future

Forest ecosystems are of global importance, ecologically, economically and culturally. However, despite their fundamental role in mitigating the worst effects of climate change, to date there have been surprisingly few resources devoted to defining, conserving and planning resilient forests for the future. Progress in this field of research, which requires international and interdisciplinary cooperation, collaboration and communication, was presented and discussed at the second biannual conference of the European Research Group, Evoltree (https://www.evoltree.eu). Over four days more than 140 scientists met to share developments and to discuss forest ecology, genetics, genomics and evolution with a focus on realising “Resilient Forests for the Future”. From examining evolutionary dynamics and using the past to understand future responses, to evaluating breeding approaches and the sustainable use of forest genetic resources, the conference addressed critical themes with relevance to this topic. The role of genomics in conservation, investigation of biotic interactions and identifying climate resilient forests were also explored. Finally, innovative methods and approaches which promise to increase the scale and speed with which forest evolutionary research can progress were introduced and evaluated. The Evoltree network and conference series provides invaluable opportunities to share knowledge and increase collaboration on forest genetic research, the need for which has never been greater or more urgent

Inferring fine-scale spatial structure of the brown bear (Ursus arctos) population in the Carpathians prior to infrastructure development

Landscape genetics is increasingly being used in landscape planning for biodiversity conservation by assessing habitat connectivity and identifying landscape barriers, using intraspecific genetic data and quantification of landscape heterogeneity to statistically test the link between genetic variation and landscape variability. In this study we used genetic data to understand how landscape features and environmental factors influence demographic connectedness in Europe’s largest brown bear population and to assist in mitigating planned infrastructure development in Romania. Model-based clustering inferred one large and continuous bear population across the Carpathians suggesting that suitable bear habitat has not become sufficiently fragmented to restrict movement of individuals. However, at a finer scale, large rivers, often located alongside large roads with heavy traffic, were found to restrict gene flow significantly, while eastern facing slopes promoted genetic exchange. Since the proposed highway infrastructure development threatens to fragment regions of the Carpathians where brown bears occur, we develop a decision support tool based on models that assess the landscape configuration needed for brown bear conservation using wildlife corridor parameters. Critical brown bear corridors were identified through spatial mapping and connectivity models, which may be negatively influenced by infrastructure development and which therefore require mitigation. We recommend that current and proposed infrastructure developments incorporate these findings into their design and where possible avoid construction measures that may further fragment Romania’s brown bear population or include mitigation measures where alternative routes are not feasible

Interspecific gene flow and maintenance of species integrity in oaks

Oak species show a wide variation in morphological and physiological characters, and boundaries between closely related species are often not clear-cut. Still, despite frequent interspecific gene flow, oaks maintain distinct morphological and physiological adaptations. In sympatric stands, spatial distribution of species with different ecological requirements is not random but constrained by soil and other micro-environmental factors. Here, we discuss factors that may influence the maintenance of the integrity of oak species in the face of interspecific gene flow. Pre-zygotic isolation (e.g. cross incompatibilities, asynchrony in flowering, pollen competition) and post-zygotic isolation (divergent selection) contribute to the maintenance of species integrity in sympatric oak stands. The antagonistic effects of interspecific gene flow and divergent selection are reflected in the low genetic differentiation between hybridizing oak species at most genomic regions interspersed by regions with signatures of divergent selection (outlier regions). In the near future, the availability of high-density genetic linkage maps anchored to scaffolds of a sequenced Q. robur genome will allow to characterize the underlying genes in these outlier regions and their putative role in reproductive isolation between species. Reciprocal transplant experiments of seedlings between parental environments can be used to characterize selection on outlier genes. High transferability of gene-based markers will enable comparative outlier screens in different oak species

TESTING BAYESIAN ALGORITHMS TO DETECT GENETIC STRUCTURE IN TWO CLOSELY RELATED OAK TAXA

The aim of this study was to test the Bayesian algorithm implemented in the software STRUCTURE in order to detect the number of clusters, by using microsatellite data from four oak species. Several assignment models, with or without a priori grouping of individuals to species, were proposed. Better results were obtained by using the sampling location information and when only two taxa were analyzed. Particularly, pedunculate oak and sessile oak formed distinct clusters whatever the assignment model we use. By contrast, no separation between the two oaks from series Lanuginosae was observed. This can be explained, on one hand, by the small sampling size for Italian oak, or by the genetic similarities of the two pubescent oaks, namely Quercus pubescens and Q. virgiliana, on the other hand. Our findings support the hypothesis according which Italian oak is an intraspecific taxonomic unit of pubescent oak

Tree Shape Variability in a Mixed Oak Forest Using Terrestrial Laser Technology: Implications for Mating System Analysis

The accuracy of the description regarding tree architecture is crucial for data processing. LiDAR technology is an efficient solution for capturing the characteristics of individual trees. The aim of the present study was to analyze tree shape variability in a mixed oak forest consisting of four European white oak species: Quercus petraea, Q. frainetto, Q. pubescens, and Q. robur. Moreover, we tested for association between tree shape and individual heterozygosity and whether oak trees identified as pollen donors in a previous genetic study have a larger size in terms of crown and trunk characteristics than non-donors. The woody structure of a tree was defined by the quantitative structure model (QSM) providing information about topology (branching structure), geometry, and volume. For extracting the 3D point clouds a high-speed 3D scanner (FARO FocusS 70) was used. The crown variables were strongly correlated to each other, the branch volume being influenced by branch length, maximum branch order, and the number of branches but not influenced by diameter at breast height (DBH), trunk length, trunk volume, or tree height. There was no relationship between the individual heterozygosity based on nuclear microsatellite genetic markers and crown and trunk characteristics, respectively. Branch volume, total area, DBH, trunk volume, and the total volume of tree were significantly larger in pollen donors compared to non-donor Q. petraea trees. Thus, the mean branch volume was more than three times higher. Pollen donors had nearly two and half times larger total area in comparison to non-donor individuals. Our results suggest that a thorough characterization of tree phenotype using terrestrial laser scanning may contribute to a better understanding of mating system patterns in oak forests