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The Accelerating Growth Rates of Central European Forest Stands

Paper Reviewed
Pretzsch, H, Biber, P., Schutze, G., Uhl, E. and Rotzer, T. 2014. Forest stand growth dynamics in Central Europe have accelerated since 1870. Nature Communications 5: 10.1038/ncomms5967.

In a rather unique study published in Nature Communications, Pretzsch et al. (2014) analyzed data that had been obtained from long-term experimental forest plots established some 140 years earlier in Central European regions where time series of temperature and precipitation date back all the way to 1781. And in doing so, they focused on 36 plots of Norway spruce (Picea abies) and 22 plots of European beech (Fagus sylvatica), as these are the dominant taxa of Central Europe's forests. Furthermore, they indicate that the plots they studied were "maintained under continuous scientific control, and surveyed on a single tree basis." So what did they find?

The five German researchers discovered that the 58 forest plots they studied currently exhibit "significantly faster tree growth (+32 to 77%), stand volume growth (+10 to 30%) and standing stock accumulation (+6 to 7%) than in 1960." They also state that "statistical analyses of the experimental plots, and application of an ecophysiological model, suggest that mainly the rise in temperature and extended growing seasons contribute to increased growth acceleration." But they additionally note, that "the rise in atmospheric CO2 concentration, the higher N-deposition [as well as the increase in air temperature] were two to three times higher in the second half of the twentieth century compared with the first half." In addition, they say that the growing season was extended by 22 days over the course of the study, with the main increase occurring over the last 50 years.

Last of all, Pretzsch et al. report that most stands "have not reached a final constant yield plateau," which suggests that they are still in the process of flexing their muscles, so to speak, coincident with "an increase in resource supply (CO2, N), together with an extended growing season accompanied by changes in other climatic variables." And they note, in this regard, that this amazing growth stimulation "surprisingly occurred during the period when acid rain (1970-1990) and drought episodes (1976 and 2003) suggest decreased productivity should have occurred."

One has to love those trees! ... which apparently love their CO2 and nitrogen, as well as the warmer weather that has accompanied their ever-increasing productivity.

Posted 13 February 2015