Logging versus fire: How does disturbance type influence the abundance of Pinus strobus regeneration?

Abstract

Eastern white pine (Pinus strobus) has decreased in abundance over the past century throughout the Great Lakes Region of North America, but the relative constraints placed on recruitment under contrasting disturbance regimes are not well understood. The objectives of this study were to determine the extent to which white pine could invade areas recently disturbed by fire or logging (within 10–28 years), and assess the relative limitations placed on recruitment by seed supply, microsite habitat, and competition. We compared white pine regeneration on 61 sites disturbed by fire or logging that were adjacent to intact mature stands that provided a seed source. White pine seedling and sapling densities declined with increasing distance from a seed source, and the rate of decrease was determined by the interaction between seed supply and variation in number and quality of safe sites. For a given combination of seed source and site, white pine seedlings were three times more abundant on burned than logged sites. White pine seedlings grew into the sapling size class more often on burned than logged sites due to lower shrub cover on burned sites. At 25 years after disturbance, regeneration densities of white pine sufficient to achieve eventual future dominance occurred up to 80 m and 20 m from the edge of mature white pine stands after fire and logging, respectively. To attain a similar level of white pine stocking after disturbance, three to four times as many patches of mature white pine need to be left after logging than after fire.