The Carbon Sink of an Old-Growth Forest in China
Tan, Z.-H., Zhang, Y.-P., Schaefer, D., Yu, G.-R., Liang, N. and Song, Q.-H. 2011. An old-growth subtropical Asian evergreen forest as a large carbon sink. Atmospheric Environment 45: 1548-1554.
Tan et al. (2011) suggest that it is not really so, reporting the fact that stands of trees with ages in excess of 200 years have been demonstrated by several research groups to act as carbon sinks in both coniferous and mixed forests, citing the work of Hollinger et al. (1994), Law et al. (2001), Roser et al. (2002), Knohl et al. (2003), Paw et al. (2004), Desai et al. (2005) and Guan et al. (2006). And they go on to buttress this claim by reporting the results of their own study of the subject, in which they employed an eddy covariance technique to examine the carbon balance of a more-than-300-year-old subtropical evergreen broadleaved forest that is located in the center of the largest subtropical land area of the world in the Ailao Mountain Nature Reserve (24°32'N, 101°01'E) of Yunnan Province in Southwest China.
There, in addition to their micrometeorologically-based eddy flux carbon budget estimation, the six scientists conducted a tree inventory of one hectare of forest located within the footprint of the eddy flux tower they employed in November of 2003 and again in November of 2007, after which they compared measurements of tree diameter at breast height (DBH) between the two times and employed site specific allometric equations to derive mean yearly biomass production from the measurements obtained at the two times, while they also assessed aboveground litter production via the amount captured each year in 25 litter traps that were randomly distributed within the one-hectare plot.
As a result of their efforts, Tan et al. determined that the mean annual net ecosystem production of the forest was approximately 9 tC/ha/year, which suggests, in their words, that "this forest acts as a large carbon sink." In addition, their inventory data indicated that about 6 tC/ha/year was contributed by biomass and necromass. And they report that approximately 60% of the biomass increment was contributed by the growth of large trees with breast height diameters in excess of 60 cm.
Clearly, the old notion of old trees contributing next to nothing to global carbon sequestration is manifestly invalid. They are ever hard at work, doing more good in this regard than all of the wrong-headed reductions in anthropogenic CO2 emissions ever to be conceived by the mind of man, and especially those minds housed in the bodies of U.S. Environmental Protection Agency policymakers, who have declared carbon dioxide to be a "dangerous air pollutant." Far from it, in fact, CO2 is what sustains earth's ancient trees, and what gives them the appetite to do what they do best ... and that is suck CO2 out of the air and grow!
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Guan, D., Wu, J.B., Zhao, X.S., Han, S.J., Yu, G.R., Sun, X.M. and Jin, C.J. 2006. CO2 fluxes over an old temperate mixed forest in northeastern China. Agricultural and Forest Meteorology 137: 138-149.
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