Background
The authors indicate that "nearly one and a half centuries ago, far-sighted Central European forest scientists established a network of long-term observational plots, many of them being under observation up to the present day."

What was done
In the words of Pretzsch et al., "in order to detect long-term stand growth changes in Central Europe, we used the records from 14 fully stocked observational plots in oak stands which date back till 1900." More specifically, they indicate that they compared "the observed development of growth and standing volume over age with common yield tables which represent the historic stand dynamics," after which they statistically analyzed "whether stand development over age (course of mean diameter, top height, current annual stand growth, standing volume, tree number, tree mortality and other stand characteristics) changed within the last century."

What was learned
The four researchers report that "compared with the past, the stands presently grow quicker and accumulate a defined standing volume earlier than a century ago," also noting that "they grow along modified self-thinning lines and move quicker through such trajectories than in the past." In fact, they determined that certain threshold sizes are reached decades earlier compared with the past, and that the level of tree growth rate vs. tree size allometry "increased significantly."

What it means
In their concluding paragraph, Pretzsch et al. suggest that with higher growth rates "rotation periods might be reduced and sustainable felling budgets might be increased," In addition, they say that "carbon sequestration by forests might increase as well," and that "on top of that, the increase of site fertility may pave the way to multi-species, complex-structured forests which are more resilient than pure stands in the face of future environmental changes."