[MCN] Increased heat associated with forest decline in western Canada

[Lance Olsen]

Global Change Biology October 2015

Net aboveground biomass declines of four major forest types with 
forest ageing and climate change in western Canada's boreal forests
Han Y. H. Chen, Yong Luo
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"Our results suggest that persistent warming and decreasing water 
availability have profound negative effects on forest biomass in the 
boreal forests of western Canada."
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Abstract
http://onlinelibrary.wiley.com/doi/10.1111/gcb.12994/full

Biomass change of the world's forests is critical to the global 
carbon cycle. Despite storing nearly half of global forest carbon, 
the boreal biome of diverse forest types and ages is a poorly 
understood component of the carbon cycle. Using data from 871 
permanent plots in the western boreal forest of Canada, we examined 
net annual aboveground biomass change (?AGB) of four major forest 
types between 1958 and 2011. We found that ?AGB was higher for 
deciduous broadleaf (DEC) (1.44 Mg ha?1 year?1, 95% Bayesian 
confidence interval (CI), 1.22-1.68) and early-successional 
coniferous forests (ESC) (1.42, CI, 1.30-1.56) than mixed forests 
(MIX) (0.80, CI, 0.50-1.11) and late-successional coniferous (LSC) 
forests (0.62, CI, 0.39-0.88). ?AGB declined with forest age as well 
as calendar year. After accounting for the effects of forest age, 
?AGB declined by 0.035, 0.021, 0.032 and 0.069 Mg ha?1 year?1 per 
calendar year in DEC, ESC, MIX and LSC forests, respectively. The 
?AGB declines resulted from increased tree mortality and reduced 
growth in all forest types except DEC, in which a large biomass loss 
from mortality was accompanied with a small increase in growth. With 
every degree of annual temperature increase, ?AGB decreased by 1.00, 
0.20, 0.55 and 1.07 Mg ha?1 year?1 in DEC, ESC, MIX and LSC forests, 
respectively. With every cm decrease of annual climatic moisture 
availability, ?AGB decreased 0.030, 0.045 and 0.17 Mg ha?1 year?1 in 
ESC, MIX and LSC forests, but changed little in DEC forests. Our 
results suggest that persistent warming and decreasing water 
availability have profound negative effects on forest biomass in the 
boreal forests of western Canada. Furthermore, our results indicate 
that forest responses to climate change are strongly dependent on 
forest composition with late-successional coniferous forests being 
most vulnerable to climate changes in terms of aboveground biomass.
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"The growth in CO2 emissions closely follows the growth in Gross 
Domestic Product (GDP) corrected for improvements in energy 
efficiency."

P. Friedlingstein, et al. "Update on CO2 emissions."
Nature Geoscience. Published online: 21 November 2010
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"An impressive study across all of northern Russia from 1953-2002 
showed a shift in tree allometries. In areas where summer 
temperatures and precipitation have both increased, a general 
increase in biomass (up 9%) is primarily a result of increased 
greenery (33% more carbon in leaves and needles), rather than woody 
parts (roots and stem). In areas that have experienced warming and 
drying trends, greenery has decreased, and both roots and stems have 
increased (Lapenis et al. 2005)."

"  ...  there is little theoretical or experimental support to 
suggest that climate warming will cause absolute climatic tolerances 
of a species to evolve sufficiently to allow it to conserve its 
geographic distribution."

Camille Parmesan. "Ecological and Evolutionary Responses to Recent 
Climate Change." Annual Review of Ecol. Evol. & Systematics  2006. 
37:637-69


















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