What was done
The authors validated the process-based TRIPLEX model of forest growth and carbon and nitrogen cycling against observed data, after which they used the calibrated model to investigate the potential impacts of projected increases in the atmosphere's CO2 content on the climate of northeast China and its interactions with the aerial fertilization effect of the increase in atmospheric CO2 in computing changes likely to occur in the net primary productivity (NPP) and carbon budget of the region's forests.

What was learned
First of all, Peng et al. report that "the model validation results show that the simulated tree total volume, NPP, total biomass and soil carbon are consistent with observed data across the Northeast of China, demonstrating that the improved TRIPLEX model is able to simulate forest growth and carbon dynamics of the boreal and temperate forest ecosystems at regional scale." Then they note that the application of the appropriately calibrated model indicates that climate change would increase forest NPP and biomass carbon but decrease overall soil carbon under all three of the climate change scenarios they studied, but that "the combined effects of climate change and CO2 fertilization on the increase of NPP were estimated to be 10-12% for [the] 2030s and 28-37% in [the] 2090s," because "the simulated effects of CO2 fertilization significantly offset the soil carbon loss due to climate change alone."

What it means
The seven scientists conclude that "overall, future climate change and increasing atmospheric CO2 would have a significant impact on the forest ecosystems of Northeastern China," and their findings clearly indicate that that impact would be beneficial. In addition, they say that "the results of the effects of CO2 fertilization on NPP simulated by TRIPLEX1.0 are consistent with the recent FACE experiments in temperate forests in North America and Europe (Norby et al., 2005), global analyses of Melillo et al. (1993) and Mathews (2007), and site-specific investigations in Canadian boreal forest ecosystems (Peng and Apps, 1998, 1999)," which consistencies lead them to additionally conclude that "the effect of CO2 fertilization on forest NPP is now firmly established." And that firmly-established effect is now a firmly-established global good.

References
Matthews, H.D. 2007. Implications of CO2 fertilization for future climate change in a coupled climate-carbon model. Global Change Biology 13: 1-11.

Melillo, J.M., McGuire, A.D., Kicklighter, D.W., Moore, B., Vorosmarty, C.J. and Schloss, A.L. 1993. Global climate change and terrestrial net primary production. Nature 363: 234-240.

Norby, R.J., DeLucia, E.H., Gielen, B., Calfapietra, C., Giardina, C.P., King, S.J., Ledford, J., McCarthy, H.R., Moore, D.J.P., Ceulemans, R., De Angelis, P., Finzi, A.C., Karnosky, D.F., Kubiske, M.E., Lukac, M., Pregitzer, K.S., Scarasci-Mugnozza, G.E., Schlesinger, W.H. and Oren, R. 2005. Forest response to elevated CO2 is conserved across a broad range of productivity. Proceedings of the National Academy of Sciences USA 102: 18,052-18,056.

Peng, C.H. and Apps, M.J. 1998. Simulating carbon dynamics along the Boreal Forest Transect Case Study (BFTCS) in the Central of Canada: II. Sensitivity to climate change. Global Biogeochemical Cycles 12: 393-402.

Peng, C.H. and Apps, M.J. 1999. Modeling response of net primary productivity (NPP) of boreal forest ecosystems to changes in climate and fire disturbance regimes. Ecological Modeling 122: 175-193.