Occurrence and management of oak in southern Swedish forests

This article describes the current proportions of forest types with oak (Quercus robur and Q. petraea) in southern Sweden, provides an overview of oak distribution over time and reviews literature about oak regeneration relevant for the region. Further we discuss silvicultural possibilities to maintain and promote oak in Scandinavia. In Götaland pure oak forest covers 1% of the forest area and mixed forest types with > 10% oak proportion cover approximately 10% of the area. Common types of mixture are spruce-oak and pine-oak forest. Both mixtures are frequent in mature forest, especially pine-oak. Additionally, about one third of spruce-oak mixtures can be found in medium-aged forest. Intensive management would be necessary to promote single oak trees in old pine stands or spruce plantations, but the proportion of oak in coniferous forest provides some potential to maintain additional oak trees. The distribution of acorns by Jays, enhanced measures against browsing, and the release of single oak trees from competing tree species could help to maintain more oak trees for nature conservation. However, regarding management of oak for timber production, conventional methods are recommended. Planting after clear cutting of coniferous forest, or short shelter periods after mast years in oak stands, are established methods to regenerate pure oak stands. Another possibility to develop mature oak forest are mixed oak-spruce plantations, as traditionally practised in a small region in southern Sweden. The different approaches of oak management in Sweden were presented in April 2012 on the annual meeting of the section silviculture of DVFFA (German Union of Forest Research Organizations) in Wermsdorf near Leipzig to give an overview and access to recent forest research in Sweden

Lignin engineering in forest trees

Wood is a renewable resource that is mainly composed of lignin and cell wall polysaccharides. The polysaccharide fraction is valuable as it can be converted into pulp and paper, or into fermentable sugars. On the other hand, the lignin fraction is increasingly being considered a valuable source of aromatic building blocks for the chemical industry. The presence of lignin in wood is one of the major recalcitrance factors in woody biomass processing, necessitating the need for harsh chemical treatments to degrade and extract it prior to the valorization of the cell wall polysaccharides, cellulose and hemicellulose. Over the past years, large research efforts have been devoted to engineering lignin amount and composition to reduce biomass recalcitrance toward chemical processing. We review the efforts made in forest trees, and compare results from greenhouse and field trials. Furthermore, we address the value and potential of CRISPR-based gene editing in lignin engineering and its integration in tree breeding programs

Tree Composition and Seedling Recruitment in Urban and Rural Forests

In 1993, Dr. Nancy Broshot randomly located 25 permanent study sites in Forest Park in Portland, Oregon to examine the effects of urbanization on forest health. Plant community structure was examined. In 2003, Dr. Broshot reexamined the plant communities at each site and found significantly higher tree mortality and reduced recruitment (young trees) in all areas of the park. Many seedlings that had been present in 1993 were absent in 2003. In 2013, a 20-year follow up study of the tree community was conducted. Although the rate of tree mortality had dropped, recruitment of seedlings and saplings was still low. A series of lichen studies completed at each site in 2013 indicated high levels of nitrogenous air pollution at all sites in the park. In 2014, three control sites along a gradient of air quality in the Mount Hood National Forest above Estacada, Oregon were added to the study. Plant community variables were measured in the same manner as in Forest Park. We found significantly more live trees, saplings and seedlings at the control sites than at sites in Forest Park. We also found significantly fewer dead trees at control sites. Indeed, we had more seedlings at the three control sites than at all 25 of the Forest Park sites. We believe the low level of recruitment may be due to nitrogenous deposition from air pollution in Forest Park; we are waiting for results from collected soil samples to evaluate this hypothesis

Is interlocked grain an adaptive trait for tropical tree species in rainforest?

Many trees in tropical rain forest exhibit interlocked grain. This phenomenon was observed, using a splitting method, on 10 trees from different genera in French Guiana. There were rather strong variations between and within trees. Different indexes were used and compared to describe this interlocked grain. Previous results have shown that the rupture energy necessary to create a radiallongitudinal surface by wood splitting grows more than 2 or 3 times with interlocked grain occurrence. Moreover, radial splitting of large tropical trees with high density wood is more prone to appear due to the decrease of the ratio between rupture energy and Young's modulus when wood density increases. Finally the long lasting high level of maturation stress in tropical trees growing in primary forest means a very high level of stored elastic energy in the trunk that could be dangerous for the living tree. Interlocked grain can be a good solution to prevent the risk of radial splitting for these adult trees. (Résumé d'auteur

Forest Measurements

Forest measurements, one of the cornerstones in the foundation of forestry, is the art and science of providing the quantitative information about trees and forest stands necessary for forest management, planning, and research. The updated edition (sixth edition) of this longstanding classic textbook, Forest Measurements, provides new and complete coverage of conventional and current measurement practices and technological applications that link the role of forest measurements with management of forest resources

Tree growth acceleration and expansion of alpine forests: The synergistic effect of atmospheric and edaphic change.

Many forest ecosystems have experienced recent declines in productivity; however, in some alpine regions, tree growth and forest expansion are increasing at marked rates. Dendrochronological analyses at the upper limit of alpine forests in the Tibetan Plateau show a steady increase in tree growth since the early 1900s, which intensified during the 1930s and 1960s, and have reached unprecedented levels since 1760. This recent growth acceleration was observed in small/young and large/old trees and coincided with the establishment of trees outside the forest range, reflecting a connection between the physiological performance of dominant species and shifts in forest distribution. Measurements of stable isotopes (carbon, oxygen, and nitrogen) in tree rings indicate that tree growth has been stimulated by the synergistic effect of rising atmospheric CO2 and a warming-induced increase in water and nutrient availability from thawing permafrost. These findings illustrate the importance of considering soil-plant-atmosphere interactions to understand current and anticipate future changes in productivity and distribution of forest ecosystems