Carlquist’s growth ring classification: a functional approach that reinforces porous and annual rings

There is no doubt that Carlquist is one of the greatest contemporary wood anatomists. Every student or researcher in the field is likely to have read at least one of his numerous works, and it is difficult to find a topic in wood anatomy that does not lead to one to his publications. Among the many topics addressed by Carlquist are of course growth rings, one of the oldest and most exciting topics in wood anatomy. Carlquist established a functional classification for growth rings based on anatomical variation, in addition to an interpretation of the different anatomical markers “as ecologically adaptive devices.” In this article, I return to Carlquist’s first classification of growth rings and summarize the main changes in his later reviews. I highlight the advances provided by his unprecedented functional approach to growth rings, while also criticizing Carlquist’s proposed growth ring classification, which reinforces a partial view, although dominant until the present day, focused on temperate species: that growth rings are mostly well marked, porous or semi-porous, and with annual periodicity.