How long do Norway spruce snags stand? Evaluating four estimation methods

We estimated time from death to fall (standing time) of Norway spruce (Picea abies (L.) Karst.) snags in a submountainous old-growth forest in south-central Norway, applying four calculation methods to 124 dendrochronologically cross-dated still-standing snags and 64 fallen logs. The calculation methods consistently estimated expected standing time of snags at 26-34 years, with a median of 16-21 years and 20% of snags standing for >48-58 years. The survival function from all methods took the approximate form of a negative exponential, with a 3%-4% annual fall rate for snags. In the distribution of time since death, a small peak in dead trees 20-30 years ago (late 1970s) coincides with a historic epidemic of bark beetles. The method using only time since death of still-standing snags appears to be the most feasible for estimating total standing time of snags in old-growth forests with constant tree mortality.