During the 19th century, the tradition of German forestry science persisted as cameralism gave way to economic liberalism. It produced the monocultural, even-age forests that eventually transformed the Normalbaum from abstraction to reality. The German forest became an archetype for imposing on disorderly nature the neatly arranged
constructs of science. Witness the forest Cotta chose as an example of his new science: over the decades, his plan transformed a ragged patchwork into a neat chessboard (fig. 11.2). Practical goals had encouraged mathematical utilitarianism, which seemed, in turn, to promote geometric perfection as the outward sign of the well-managed forest; in turn, the rationally ordered arrangement of trees offered new possibilities for controlling nature. For example, the technique of periodic area allotment (Flächenfachwerk ) favored by Cotta generated the now familiar checkerboard scheme of growth periods. The mathematical exercise that generated the pattern could be modified to order the sequence of cutting so that older stands protected younger trees against prevailing winds. In the hands of a suitably trained forester, mathematical order and practical utility became one enterprise.
During the 19th century, Forstwissenschaft advanced along the lines established by the early forest mathematicians: sustained yield, regulation according to age-classes and wood mass, and construction of the "normal forest" as an artifact of mathematical reasoning applied to quantitative data. By the end of the 19th century, reformers of forestry in other natiøns—France, England (via the Indian Forest Service under Sir Dietrich Brandis), and the United States—had also discovered the need for conservation and forest management based on professional training and scientific principles. In each country, beginning with France during the 1820s and culminating with the American conservation movement, the inspiration and example was German Forstwissenschaft .
In Germany, however, resistance to the mathematically formulated forest economy began to grow, spurred by natural devastations caused largely by strict reliance on monocultures. By the end of the 19th century, foresters such as Karl Gayer, inspired by new-found loyalty to the natural diversity of species, called for turning "back to nature." Careful consideration of the forest as a multi-faceted biological ecosystem came into vogue. Even in the face of this opposition, quantitative techniques elaborated by the Forstklassiker survived in practice. Above all, the doctrine of sustained yield remained sacrosanct. Franz Heske, writing in 1938 for American foresters, reaffirmed the legacy of 19th-century Forstwissenschaft based on the work of the classical writers:
For all time, this century [the 19th] of systematic forest management in Germany, during which the depleted, abused woods were transformed into well-managed forests with steadily increasing yields, will be a shining example for forestry in all the world. German experience over a century makes it considerably easier for the rest of the world to pursue a similar course, because the attainable goal is now known, at least in principle. The sponsors of sustained-yield management in countries where forestry is still new can find in the results of this large-scale German experiment a strong support in their battle with those who know nothing, who believe nothing, and who wish to do nothing. This experiment and its outcome have rendered inestimable service in the cause of a regulated, planned development and use of the earth's raw materials, which will be an essential feature of the coming organic world economy.