ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Jill Johnstone
Authors   Jill Johnstone and F. S. Chapin, III
Category   Life Science
Title   Non-Equilibrium Succession Dynamics Indicate Continued Northern Migration of Lodgepole Pine
Affiliation   Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA

Abstract

Because species affect ecosystem functioning, understanding migration processes is a key component of predicting future ecosystem responses to climate change. This study provides evidence of range expansion under current climate conditions of an indigenous species with strong ecosystem effects. Surveys of stands along the northern distribution limit of lodgepole pine (Pinus contorta var. latifolia) in central Yukon Territory, Canada showed consistent increases in pine dominance following fire. These patterns differed strongly from those observed at sites where pine has been present for several thousand years. Differences in species thinning rates are unlikely to account for the observed increases in pine dominance. Rates of pine regeneration at its range limits were equivalent to those of spruce, indicating a capacity for rapid local population expansion. The study also found no evidence of strong climate limitation of pine population growth at the northern distribution limit. These data are interpreted as evidence of current pine expansion at its range limits, and imply that the northern distribution of lodgepole pine is not in equilibrium with current climate conditions. The migration dynamics of lodgepole pine have important implications for ecosystem functioning because of pine’s effects on fire regime, carbon storage, and productivity in boreal forest.