The journal news feed presents key findings from selected scientific articles from SNS’ scientific journal Scandinavian Journal of Forest Research. The summaries are personal interpretations of the content made by the editor of News & Views.
The journal news feed from Scandinavian Journal of Forest Research (SJFR) Volume 30, troche Issue 4, 2015 reviews four new interesting research articles.
Download the latest journal news feed here!
Browsing prevents aspen and rowan from growing large
Intensified levels of ungulate browsing have raised concerns over the recruitment of aspen and rowan in boreal forests in Sweden. In a five-year study, the growth of young aspens and rowans was compared within and outside fences. Outside fences, 20 to 40% of the trees below 1 m tall were browsed, and a slightly lower proportion of trees 1-2 m. Aspens were browsed harder than rowans when very young, but later the reverse was true. Transition to the ungulate-safe height (>3 m) was reduced by a factor of two in rowan and four in aspen due to browsing. However, it is still not known whether aspens and rowans are “overgrazed” from a conservation point of view. The question remains whether organisms dependent on mature growth stages of aspen and rowans can be sustained over extended periods of time at the current browsing rate.
Read more in: Edenius, L. & Ericsson, G. 2015. Effects of ungulate browsing on recruitment of aspen and rowan: a demographic approach. Scand J For Res 30(4), 283-288.
Models predict thinning responses on oak crowns
Thinning guidelines for different kinds of trees are often based on crown size. To improve understanding of the crown response of pendunculate oak (Quercus robur) to different thinning practices, a study was carried out involving nine thinning experiments in Sweden, Denmark and Great Britain. Stem size, stand density and site productivity were measured in even-aged stands and run through various models. The results from the study indicate that the crown radius increases with increased diameter at breast height, increased thinning grade (decreasing stand density) and decreased site productivity. The models are valid for predicting the crown radius of pedunculate oak in even-aged forest stands.
Read more in: Attocci, G. & Skovsgaard J. P. 2015. Crown radius of pendunculate oak (Quercus robur L.) depending on steam size, stand density and site productivity. Scand J For Res 30(4), 289-303.
Mixed forests even out growth variation
It has been claimed that mixed forests are more productive than monocultures. An experimental comparison of the productivity of mixed stands and corresponding monocultures in southern Sweden indicates that the mixed and pure species (monocultures) plots do not differ in average growth. The experiment involved measurements at 15 years of age, and included mostly native Swedish trees, plus Populus and Larix hybrids. However, monocultures do vary more in their growth levels compared with the mixtures – mixing two or more species can be a way to reduce the risk of failure due to damage to one species. Specific analyses were conducted for Picea abies, for which tree species mixtures tended to reduce production, and Quercus robur, for which mixtures tended to increase production.
Read more in: Drössler, L. et al. 2015. Early development of pure and mixed tree species plantations in Snogeholm, southern Sweden. Scand J For Res 30(4), 304-316.
Forest fires in Portugal – a growing problem
Forest fires have affected, on average, 3 % of the forest land each year in Portugal over the last 30 years. The compulsory afforestation of previously open land, rapid changes in society and abandonment of old rural practices all contribute to the increased number of forest fires. A study based on interviews and questionnaires completed by different stakeholders, forest owners and members of the public showed a consensual view of anthropogenic reasons for fire – negligence or arson – alongside the lack of cleanliness in the woods, which causes forest fires to spread rapidly. A greater understanding of social perceptions is important to reduce conflicts of interest, and promote a greater consensus about the goals and fundamental actions of sustainable forest management.
Read more in: Riberio, C. et al. 2015. A look at forest fires in Portugal: technical, institutional, and social perceptions. Scand J For Res 30(4), 317-325.