Articles containing the keyword 'risk model'

Within the European Community snow damage affects an estimated 4 million m³ of timber every year, causing significant economic losses to forest owners. In Northern Europe, for example, the occurrence of snow damage has increased over the last few decades mainly due to the increase in total growing stock. The most common form of damage is stem breakage, but trees can also be bent or uprooted. Trees suffering snow damage are also more prone to consequential damage through insect or fungal attacks.

Snow accumulation on trees is strongly dependent upon weather and climatological conditions. Temperature influences the moisture content of snow and therefore the degree to which it can accumulate on branches. Wind can cause snow to be shed, but can also lead to large accumulations of wet snow, rime or freezing rain. Wet snow is most likely in late autumn or early spring. Geographic location and topography influence the occurrence of damaging forms of snow, and coastal locations and moderate to high elevations experience large accumulations. Slope plays a less important role and the evidence on the role of aspect is contradictory. The occurrence of damaging events can vary from every winter to once every 10 years or so depending upon regional climatology. In the future, assuming global warming in northern latitudes, the risk of snow damage could increase, because the relative occurrence of snowfall near temperatures of zero could increase.

The severity of snow damage is related to tree characteristics. Stem taper and crown characteristics are the most important factors controlling the stability of trees. Slightly tapering stems, asymmetric crowns, and rigid horizontal branching are all associated with high risk. However, the evidence on species differences is less clear due to the interaction with location. Management of forests can alter risk through choice of regeneration, tending, thinning and rotation. However, quantification and comparison of the absolute effect of these measures is not yet possible. An integrated risk model is required to allow the various locational and silvicultural factors to be assessed. Plans are presented to construct such a model, and gaps in knowledge are highlighted.

• Nykänen, E-mail: mn@mm.unknown
• Broadgate, E-mail: mb@mm.unknown
• Kellomäki, E-mail: sk@mm.unknown
• Peltola, E-mail: hp@mm.unknown
• Quine, E-mail: cq@mm.unknown

Ungulate browsing results in important damages on the forests, affecting their structure, composition and development. In the present paper, we examine the occurrence of browsing damage in Norwegian forests, using data provided by the National Forest Inventory along several consecutive measurements (entailing the period 1995–2014). A portfolio of variables describing the stand, site and silvicultural treatments are analyzed using classification trees to retrieve combinations related to browsing damage. Our results indicate that the most vulnerable forest stands are young with densities below 1400 trees ha^–1 and dominated by birch, pine or mixed species. In addition, stand diversity and previous treatments (e.g. thinnings) increase the damage occurrence and other variables, like stand size, could play a role on forest susceptibility to browsing occurrence although the latter is based on weaker evidence. The methods and results of our study can be applied to implement management measures aiming at reducing the browsing damages of forests.

• Díaz-Yáñez, School of Forest Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland http://orcid.org/0000-0003-3829-5759 E-mail: olalla.diaz@gmail.com
• Mola-Yudego, Norwegian Institute of Bioenergy Research, P.O. Box, 115, 1431 Ås, Norway; School of Forest Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland http://orcid.org/0000-0003-0286-0170 E-mail: blas.mola@uef.fi
• González-Olabarria, Forest Sciences Centre of Catalonia (CTFC-CEMFOR), Ctra. de St. Llorenç de Morunys, km 2, 25280 Solsona, Spain http://orcid.org/0000-0002-5040-712X E-mail: jr.gonzalez@ctfc.es