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U.S. Mid-Atlantic Temperate Forest Growth Over the 20th Century
Pan, Y., Birdsey, R., Hom, J. and McCullough, K. 2009. Separating effects of changes in atmospheric composition, climate and land-use on carbon sequestration of U.S. Mid-Atlantic temperate forests. Forest Ecology and Management 259: 151-164.

What was done
The authors examined "how changes in atmospheric composition (CO2, O3 and N deposition), climate and land-use affected carbon dynamics and sequestration in Mid-Atlantic temperate forests during the 20th century," by modifying and applying "a well established process-based ecosystem model with a strong foundation of ecosystem knowledge from experimental studies," which they validated "using the U.S. Forest Inventory and Analysis (FIA) data."

What was learned
For previously harvested and currently regrowing forests, the calibrated model produced the following percentage changes in net ecosystem productivity (NEP) due to observed changes in N deposition (+32%), CO2 (+90%), O3 (-40%), CO2 + O3 (+60%), CO2 + N deposition (+184%), and CO2 + N deposition + O3 (+138%), while corresponding changes in NEP for undisturbed forests were +18%, +180%, -75%, +78%, +290%, +208%. In addition, the results of Pan et al. revealed that "the 'fertilization' effect of N deposition mainly stimulates carbon allocation to short-lived tissues such as foliage and fine roots," but that "the 'fertilization' effect by elevated CO2 likely enhances more sustainable carbon storage such as woody biomass (including coarse roots)."

What it means
In discussing the future implications of their findings, the four USDA Forest Service scientists say they indicate that "the change in atmospheric composition, particularly elevated CO2, will gradually account for more of the carbon sink of temperate forests in the Mid-Atlantic region," and they opine that "such a significant 'fertilization effect' on the forest carbon sequestration could eventually result in a 'greener world' after a long period of chronic change in atmospheric composition and cumulative impact."

Reviewed 15 September 2010