New mortality models were developed for the purpose of improving long-term growth andyield simulations in Finland, Norway, and Sweden and were based on permanent national forestinventory plots from Sweden and Norway. Mortality was modelled in two steps. The first modelpredicts the probability of survival, while the second model predicts the proportion of basal areain surviving trees for plots where mortality has occurred. In both models, the logistic function wasused. The models incorporate the variation in prediction period length and in plot size. Validationof both models indicated unbiased mortality rates with respect to various stand characteristicssuch as stand density, average tree diameter, stand age, and the proportion of different tree species, Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and broadleaves.When testing against an independent dataset of unmanaged spruce-dominated stands in Finland,the models provided unbiased prediction with respect to stand age.
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