Data from: Drivers of snag fall rates in Fennoscandian boreal forests

Persistence of standing dead trees (snags) is an important determinant for
their role for biodiversity and dead wood associated carbon fluxes. How
fast snags fall varies widely among species and regions and is further
influenced by a variety of stand- and tree-level factors. However, our
understanding of this variation is fragmentary at best, partly due to lack
of empirical data. Here, we took advantage of the accruing time
series of snag observations in the Finnish, Norwegian, and Swedish
National Forest Inventories that have been followed in these programs
since the mid-1990s. We first harmonized observations from slightly
different inventory protocols and then, using this harmonized dataset of
ca. 43 000 observations that had a consistent 5-year census interval, we
modeled the probability of snags of the main boreal tree
species Pinus sylvestris, Picea abies, and Betula spp. falling,
as a function of tree- and stand-level variables, using Bayesian logistic
regression modeling. The models were moderately good at
predicting snags remaining standing or falling, with a correct
classification rate ranging from 68% to 75% among species. In
general, snag persistence increased with tree size and climatic wetness,
and decreased with temperature sum, advancing stage of decay, site
productivity, and disturbance intensity (mainly harvesting). Synthesis and
applications. The effect of harvesting demonstrates that an efficient
avenue to increase the amount of snags in managed forests is protecting
them during silvicultural operations. In the warmer future, negative
relationship between snag persistence and temperature suggests decreasing
the time snags remain standing and hence decreasing habitat availability
for associated species. As decomposition rates generally increase after
fall, decreasing snag persistence also implies substantially faster
release of carbon from dead wood.