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Biomass and leaf area equations are often required to assess or model forest productivity, carbon stocks and other ecosystem services. These factors are influenced by climate, age and stand structural attributes including stand density and tree species diversity or species composition. However, such covariates are rarely included in biomass and leaf area equations. We reviewed the literature and built a database of biomass and leaf area equations for 24 European tree species and 3 introduced species. The final dataset contained 973 equations. Most of the equations were site-specific and therefore restricted to the edaphic, climatic and stand structural conditions of the given site. To overcome this limitation, the database was used to develop regional species-specific equations that can be used in a wide range of stands and to quantify the effects of climate, age and stand structure on biomass or leaf area. The analysis showed considerable inter-and intra-specific variability in biomass relationships. The intra-specific variability was related to climate, age or stand characteristics, while the inter-specific variability was correlated with traits such as wood density, specific leaf area and shade tolerance. The analysis also showed that foliage mass is more variable than stem or total aboveground biomass, both within and between species, and these biomass components have contrasting responses to age and changes in stand structure. Despite the large number of published equations, many species are still not well represented. Therefore, generic equations were developed that include species-specific wood density instead of species identity. Further improvements may be possible if future studies quantify the stand structure of individual tree neighbourhoods instead of using the stand means for all trees sampled with the given stand.

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Oaks (Quercus spp.) are becoming increasingly important for future forest management as the climate in central Europe warms. Owing to the high costs of conventional row planting, artificial oak stand establishment in the form of "clusters" became popular in central Europe beginning in the 1970s. In cluster plantings, oaks are planted either in groups of ca. 20-25 at 1 m spacing between trees (i.e., group planting) or in denser groups with 20-30 oaks·m −2 (i.e., nest planting). In both cases, the clusters are spaced apart at a distance that represents the target density of future crop trees. A comprehensive review of the history, growth, tree quality development, and economic aspects of oak cluster plantings suggests that initial growing space was the most important factor influencing development of oaks in clusters. Consequently, survival, growth, quality, and biomass production were comparable in group and row plantings but lower in nest plantings. In addition, group plantings resulted in greater stand-level tree species diversity than nest or row plantings. We conclude that oak group planting is a comparatively inexpensive option for the artificial regeneration of oak-dominated broadleaved forests for a range of situations such as reforestation of disturbed areas or the afforestation of abandoned agricultural land. Future research needs regarding development and tending of forests established by oak group planting are highlighted.Key words: oak regeneration, tree quality and growth, species diversity and productivity, plant competition, forest restoration.Résumé : L'importance des chênes (Quercus spp.) pour l'aménagement forestier du futur augmente avec le réchauffement du climat de l'Europe centrale. En raison des coûts élevés de la plantation conventionnelle en rangée, l'établissement de chênaies artificielles selon une répartition par grappes est devenu populaire en Europe centrale au cours des années 1970. Dans les plantations en grappes, les chênes sont plantés en groupes d'environ 20 à 25 avec un espacement d'un mètre entre les arbres (c.-à -d. la plantation en groupes) ou en groupes plus denses de 20 à 30 chênes par m 2 (c.-à -d. la plantation en nids). Dans les deux cas, l'espacement entre les grappes est déterminé de façon à obtenir la densité cible des arbres d'avenir. Une analyse complète de l'histoire, de la croissance, du développement de la qualité des arbres et des aspects économiques de la plantation de chênes en grappes indique que l'espacement initial entre les plants est le facteur qui influence le plus le développement des chênes dans les grappes. Ainsi, la survie, la croissance, la qualité et la production de biomasse étaient semblables dans les plantations en groupes et en rangées, mais étaient moindres dans les plantations en nids. De plus, à l'échelle du peuplement, une plus grande diversité en espèces d'arbres a été observée dans les plantations en groupes comparativement aux plantations en nids ou en rangées. Nous concluons que la plantation de chênes en groupes est une opti...

Scientific studies have shown that mixed forests of silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) provide higher ecosystem services than monospecific forests. Mixed forests are known for their high resilience to climate change impacts and superior biodiversity compared to monospecific forests. Despite this superiority, the transformation from monospecific to mixed forests can meet socio-technical challenges that are manifested in dissent or even in conflicts. The integration of stakeholders and citizens plays a key role in analyzing their perceptions and views of forest transformation. Their knowledge is required to co-design and implement socially acceptable options and pathways to increase the share of mixed forests. Based on a survey in Southwest Germany, we analyzed stakeholders’ and citizens’ perceptions of ecosystem services of monospecific and mixed forests of silver fir and beech. The findings show that people believe that mixed forests provide better cultural, regulating, and supporting ecosystem services than monospecific forests. However, provisioning services were perceived as being equally or even better provided by monospecific forests. The assumed abundance of old trees and the feelings of pleasantness especially influenced the superior perception of ecosystem services provided by mixed forests. The results indicate that there is public support for the transformation of monospecific silver fir and beech forests into mixed forests in Southwest Germany.

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