Mammal Community Assembly During Primary Succession on the Pumice Plain at the Mount St. Helens Volcano (1983–2015)

Abstract

The 1980 eruption of Mount St. Helens created an outstanding opportunity to investigate mammal community assembly during primary succession. From 1983 through 2015, we documented the arrival of 34 of the 45 mammals in the regional species pool and the successful establishment of 25 species. The majority of small mammals that established were likely derived from source populations that survived in isolated refugia in adjacent areas that were less disturbed during the eruption, requiring dispersal distances of a few to several kilometers. In contrast, large mammals arrived from more distant source populations—tens of km away. The next important transition in mammal community assembly will likely occur in three or four decades, as shrub cover and coniferous tree density increases, leading to development of open-forest conditions that provide habitat for forest-associated species not yet established and concomitant decline of early-seral mammal species.