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Old Growth Forests of Northeast China
Zhou, L., Dai, L., Wang, S., Huang, X., Wang, X., Qi, L., Wang, Q., Li, G., Wei, Y. and Shao, G. 2011. Changes in carbon density for three old-growth forests on Changbai Mountain, Northeast China: 1981-2010. Annals of Forest Science 68: 953-958.

For many years it had been assumed that forests reached their maximum productivity at an intermediate age, and that productivity declined thereafter in mature and old-growth stands, ultimately becoming neutral in terms of carbon sequestration or even negative, as they changed from carbon sinks to carbon sources. In recent years, however, this view has been radically revised, as several studies have demonstrated that very old stands of trees still function as sinks of atmospheric carbon, as demonstrated by the recent study of Zhou et al.

What was done
Noting that "old-growth forests on Changbai Mountain have been well protected from human activities and provide a living laboratory for studying forest carbon sequestration under natural environmental conditions," the ten researchers say that they "used data from permanent plots measured periodically in 1981 and 2010 to quantify carbon densities for Korean pine-broadleaf mixed forest, coniferous forest and Erman's birch forest on Changbai Mountain" in "one of the largest nature reserves in China," which occupies the area between latitudes 41°43' and 42°26'N and longitudes 127°42' and 128°17'E.

What was learned
Zhou et al. report that "from 1981 to 2010, the mixed, coniferous and birch forests on Changbai Mountain experienced increases in above-ground, below-ground and total carbon densities," such that "the total carbon densities of the three old-growth forests increased by 84, 29 and 55 tons of carbon per hectare, respectively," which increases were even greater than those of the old-growth forests studied by Harmon et al. (2004) and Luyssaert et al. (2008).

What it means
Contrary to what had long been believed by many, Zhou et al. say their findings are "consistent with the suggestion of Luyssaert et al. (2008) and Zhou et al. (2006) that old-growth forests can continue to accumulate carbon," which fact has now been proven to be the case in several other studies as well, as is clearly demonstrated by the materials we have archived under the heading of Forests (Old) in our Subject Index.

Harmon, M.E., Bible, K., Ryan, M.J., Shaw, D.C., Chen, H., Klopatek, J. and Li, X. 2004. Production, respiration and overall carbon balance in an old-growth Pseudotsuga/Tsuga forest ecosystem. Ecosystems 7: 498-512.

Luyssaert, S., Schulze, E.D., Borner, A., Knohl, A., Hessenmoller, D., Law, B.E., Ciais, P. and Grace, J. 2008. Old-growth forests as global carbon sinks. Nature 455: 213-215.

Zhou, G.Y., Liu, S.G., Li, Z.A., Zhang, D.Q., Tang, X.L., Zhou, C.Y., Yan, J.H. and Mo, J.M. 2006. Old-growth forests can accumulate carbon in soils. Science 314: 1417.

Reviewed 23 November 2011