Models to assess the risk of snow and wind damage in pine, spruce, and birch forests in Sweden

Each year damage to forests caused by snow and wind causes high economic lo sses. In Sweden, approximately 4 million m(3) are damaged annually by snow and wind, roughly corresponding to a value of US$150 million, and in Europe , the damage amounts to hundreds of millions of US dollars each year. To he lp to reduce these losses, tools for risk assessment within forest manageme nt have been developed. Predictions were developed of the risk of damage fr om snow and wind to Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and Birch (Betula spp. L.) plots using tree, stand, and site characteristics. The data were obtained from 6756 permanent sample plo ts within the Swedish National Forest Inventory, which were inventoried twi ce at five-year intervals between 1983 and 1992. input data for model devel opment used measurements from the first inventory of tree characteristics f or the largest sample tree, stand, and site data, and records of snow and w ind damage from the second inventory. Models were developed for three diffe rent regions for pine- and spruce-dominated sites, while models for the who le country were developed for birch sites. In general the estimated proport ion of damaged plots was highly overestimated (31.7%-56.2%), compared with the observed proportion of 3.4%-11.9%. The models for Norway spruce compris ing tree, stand, and site data show the best predictability of damaged plot s, with 60.6%-67.6% of plots correctly classified. It is concluded that the models developed can be used to detect sites with a high probability of da mage from snow and wind, and thus be used as tools to reduce future damage and costs in practical forestry.