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Can the past predict the future? Insights from tree ring responses to climate in northern boreal forests

January 15, 2015


Xanthe Walker, Ph.D. Candidate
Dept. of Biology
University of Saskatchewan

Thursday, January 15 @ 12:00 a.m..
Geology Rm. 255

Title: Can the past predict the future? Insights from tree ring responses to climate

ABSTRACT: Unprecedented rates of climate change have increased forest stress and mortality worldwide. Tree growth responses to recent climate warming may signal changes in the susceptibility of forest communities to compositional change and consequently impact a wide range of ecosystem processes and services. In this study, I explored relationships between climate and radial growth of black spruce, a dominant tree species typical of cool and moist habitats in the boreal forests of North America. I found widespread negative correlations between growth and temperature, which I interpreted as drought stress. To test this interpretation I examined stable carbon isotope composition of tree rings. My results highlight the prominence of drought stress in the boreal forest, even for trees located in cool and moist landscape positions. As mature trees might be able to survive in stressful environmental conditions that do not permit successful recruitment and survival of seedlings, drought stressed individuals may be an indication of decreased ecosystem resilience. Thus with disturbance from fire, boreal forest stands may be less likely to recover to prefirestand densities. I explored possible linkages between drought stress in prefiretrees and postfireforest compositional changes. My results suggest that stands experiencing drought stress show the largest compositional changes and lowest resilience to disturbance. I conclude that if temperatures continue to warm, we can expect drought induced growth reductions and decreased resilience to disturbance throughout the northern boreal forest.