HR: 08:45h
AN: GC11B-04    [Abstracts]
TI: Climate change in Canadian forests: Effect of global warming and CO2 fertilization on natural populations of black and white spruce
AU: * Nelson, E A
EM: liz.nelson@utoronto.ca
AF: University of Toronto, 33 Willcocks St, Toronto, ON M5A4T3, Canada
AU: Thomas, S C
EM: sc.thomas@utoronto.ca
AF: University of Toronto, 33 Willcocks St, Toronto, ON M5A4T3, Canada
AB: Global increases in temperature and atmospheric CO2 concentration are predicted to enhance tree growth in the short term, but studies of current impacts of climate change on Canada's forests are limited. This study examined the effects of increasing temperature and atmospheric CO2 concentration on tree ring growth in west-central Manitoba and northern Ontario, sampling white spruce (Picea glauca) and black spruce (Picea mariana), respectively. Over 50 tree cores from each site were sampled, analysed for ring-width, cross-dated and detrended, generating a ~100 y chronology for each population. We found a positive correlation between ring-width increment and spring temperatures (April-May: p<0.005) in Ontario. In Manitoba, however, we found a negative correlation between summer temperatures (Jul-Aug: p<0.005) and ring-width increment coincident with a positive relationship with summer precipitation (July: p<0.03). We examined the residuals following a regression with temperature for a positive trend over time, which has been interpreted in prior studies as evidence for a CO2 fertilization effect. We detected no such putative CO2 fertilization signal in either spruce population. Our results suggest that temperature-limited lowland black spruce communities may respond positively to moderate warming, but that water-limited upland white spruce communities may suffer from drought stress under high temperature conditions. Neither population appears to benefit from increasing CO2 availability.
DE: 0428 Carbon cycling (4806)
DE: 0476 Plant ecology (1851)
DE: 1630 Impacts of global change (1225)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1699 General or miscellaneous
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting