Forest carbon cycles play an important role in efforts to understand and mitigate climate change. Large amounts of carbon (C) are stored in deep mineral forest soils, but are often not considered in accounting for global C fluxes because mineral soil C is commonly thought to be relatively stable. We explore C fluxes associated with forest management practices by examining existing data on forest C fluxes in the northeastern US. Our findings demonstrate that mineral soil C can play an important role in C emissions, especially when considering inten- sive forest management practices. Such practices are known to cause a high aboveground C flux to the atmo- sphere, but there is evidence that they can also promote comparably high and long-term belowground C fluxes. If these additional fluxes are widespread in forests, recommendations for increased reliance on forest biomass may need to be reevaluated. Furthermore, existing protocols for the monitoring of forest C often ignore mineral soil C due to lack of data. Forest C analyses will be incomplete until this problem is resolved.
Keywords: carbon accounting, deep soil mineral carbon, Forest carbon pool assessments, forest soil, stand level carbon dynamics
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Historical evidence shows that atmospheric greenhouse
gas (GhG) concentrations increase during periods of
warming, implying a positive feedback to future climate
change. We quantified this feedback for CO2 and CH4 by
combining the mathematics of feedback with empirical icecore
information and general circulation model (GCM)
climate sensitivity, finding that the warming of 1.5 –4.5C
associated with anthropogenic doubling of CO2 is amplified
to 1.6– 6.0C warming, with the uncertainty range deriving
from GCM simulations and paleo temperature records.
Thus, anthropogenic emissions result in higher final GhG
concentrations, and therefore more warming, than would be
predicted in the absence of this feedback. Moreover, a
symmetrical uncertainty in any component of feedback,
whether positive or negative, produces an asymmetrical
distribution of expected temperatures skewed toward higher
temperature. For both reasons, the omission of key positive
feedbacks and asymmetrical uncertainty from feedbacks, it
is likely that the future will be hotter than we think.
Citation: Torn, M. S., and J. Harte (2006), Missing feedbacks,
asymmetric uncertainties, and the underestimation of future
warming.
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