The scaling of respiratory metabolism with body mass is one of the most pervasive phenomena in biology. Using a single allometric equation to characterize empirical scaling relationships and to evaluate alternative hypotheses about mechanisms has been controversial. We developed a method to directly measure respiration whole plants, spanning eleven orders of magnitude in body mass, from small seedlings to large trees, and from tropical to boreal ecosystems. Our measurements include the roots, which have often been ignored.

For evaluation of whole-tree respiration, we selected variously-sized trees spanning from the smallest to the largest trees in each forest. In that way, we were able to show the maximal variation of individual respiration rates in the general plant metabolic scaling. However, it must be noted that in any forest community the smallest trees are not always the depressed trees. Therefore, some of the smallest trees have much of adventitious branches and roots adapted with the environments under a canopy gap, and relatively high specific respiration rates per individual weight in contrast to dominant trees. Such smaller trees may also play an important role in keeping the sustainability of a natural forest community. Thus, the intra-specific flexibility of individual metabolism gathers into the inter-specific robustness of metabolic scaling through various plant communities.