Genetic parameters were estimated for the diameter–height (d-h) relationship and three other tree stem-form characteristics (total height, breast height diameter, and total tree volume) for data from 10 diallel progeny trials of Scots pine ( Pinus sylvestris L.), at about 30 years of age in Sweden. Linear mixed models were fit to the data, where adjustments for intertree competition and microsite heterogeneity were made by means of covariates in a nearest-neighbour analysis. The d-h relationship was analyzed with a covariate (tree height) adjusted model of diameter. Average estimates of the additive coefficient of variation and narrow-sense heritability for the d-h relationship were 7.4% and 0.22, respectively. Estimates of dominance were comparatively small (average dominance: phenotypic variance ratio of 0.04). The results indicate that there is scope to modify the d-h relationship by selection and breeding. Additive genetic correlations between the d-h relationship and height were negative, with a mean of –0.62. Selection for height would thus result in stems that are more slender than average, suggesting that tall trees allocate relatively more resources to height growth than to diameter growth. Selection based on height alone will negatively affect volume gain.

Europe has a history rich in examples of successful and problematic introductions of trees with a native origin outside of Europe (non-native trees, NNT). Many international legal frameworks such as treaties and conventions and also the European Union have responded to the global concern about potential negative impacts of NNT that may become invasive in natural ecosystems. It is, however, national and regional legislation in particular that affects current and future management decisions in the forest sector and shapes the landscapes of Europe. We identified all relevant legal instruments regulating NNT, the different legal approaches and the regulatory intensity in 40 European countries (no microstates). Information on hard and effective soft law instruments were collected by means of a targeted questionnaire and consultation of international and national legislation information systems and databases. In total, 335 relevant legal instruments were in place in June/July 2019 to regulate the use of NNT in the investigated 116 geopolitical legal units (countries as well as sub-national regions with their own legislation). Countries and regions were empirically categorized according to ad hoc-defined legislation indicators. These indicators pay respect to the general bans on the introduction of non-native species, the generally allowed and prohibited NNT, approval mechanisms and specific areas or cases where NNT are restricted or prohibited. Our study revealed a very diverse landscape of legal frameworks across Europe, with a large variety of approaches to regulating NNT being pursued and the intensity of restriction ranging from very few restrictions on species choice and plantation surface area to the complete banning of NNT from forests. The main conclusion is that there is a clear need for more co-ordinated, science-based policies both at the local and international levels to enhance the advantages of NNT and mitigate potential negative effects.

Non-native forest tree species have been introduced in Europe since the 16th century, but only in the second half of the 20th century the significance of the seed source origin for their economic use was recognized, resulting in the establishment of numerous provenance trials at a national, regional, European and International level, as those led by IUFRO. Breeding programs have also been launched in the continent for the most economically important species. Aim of this work is the formulation of provenance recommendations for planting of five non-native tree species in Europe (Douglas fir, grand fir, Sitka spruce, lodgepole pine and black locust), based on the information obtained from twenty countries, in the frame of the EU FP-1403 NNEXT Cost Action. The survey revealed that official and non-official national recommendations, based on provenance research results, have been elaborated and followed at a different level and extend for the above five species, but only for Douglas fir recommendations exist in almost all the participating to the survey countries. The compilation of provenance recommendations across Europe for each species is presented in the current work. Besides the recommended introduced seed sources, European seed sources are also preferred for planting, due to ease of access and high availability of forest reproductive material. European breeding programs yielding genetic material of high productivity and quality constitute currently the seed source of choice for several species and countries. Consolidation of trial data obtained across countries will allow the joint analysis that is urgently needed to draw solid conclusions, and will facilitate the development of ‘Universal-Response-Functions’ for the species of interest, rendering possible the identification of the genetic material suitable for global change. New provenance trial series that will test seed sources from the entire climatic range of the species, established in sites falling within and outside the environmental envelopes of their natural ranges, are urgently needed to pinpoint and understand the species-specific climate constraints, as well as to correlate functional traits to the seed origin and the environmental conditions of the test sites, so that the selection of suitable forest reproductive material of non-native tree species in the face of climate change can be feasible.

Possibilities for early selection of clones for future seed cone production were studied in a clonal seed orchard of Scots pine (Pinus sylvestris L.) in northern Sweden over the first 30 years following establishment. The annual data were modelled as series of bivariate analyses. The correlations between cone production of clones in any individual year and that of a previous year, and cumulative cone production over all years were studied. The corresponding multivariate analysis for a full data fit simultaneously was best estimated with a genetic distance-based power model (AR). The genetic (variation among clones) and environmental variation were of the same magnitude. The genetic correlations were larger than the phenotypic correlations and both increased with orchard age. Basing selection of clones on a single observation at an early age to improve future cone production was not effective, but efficiency increased if cumulative cone count over many years was used. Year-to-year genetic correlations indicated that early forecasts by clone of cone production at mature ages are highly uncertain. Reliable predictions (moderate correlations) could be achieved only if based on rather mature grafts, 14 or more years after establishment.

Douglas fir is expected to play an increasingly important role in Swedish forestry under a changing climate. Thus far, seed orchards with clones of phenotypically selected trees (plus trees) have been established to supply the market with highly qualitative reproductive material. Given the high genetic variation of the species, its growth properties are significantly affected by the provenance. Here, we applied microsatellite markers to identify the origin of clones selected within the Swedish breeding programme. Moreover, we analysed the timing of bud burst in open-pollinated families of these clones. In particular, we aimed to explain the provenance effect on phenology by using molecular identification as a proxy. A Bayesian clustering analysis with microsatellite data enabled the assignment of the clones to one of the two varieties and also resolved within-variety origins. The phenological observations indicated an earlier bud burst of the interior variety. Within the coastal variety, the northern provenances exhibited a later bud burst. We found a significant effect of the identified origin on bud burst timing. The results of this study will be used to support further breeding efforts.