Whether relative respiration in trees can be constant: a discussion of a scaling hypothesis

TL;DR

This paper investigates whether the relative respiration rate per surface area in trees remains constant across different sizes, finding evidence that it slightly increases with tree size, challenging the hypothesis of constancy.

Contribution

It provides a comparative analysis of existing data to examine the constancy of relative respiration in trees, highlighting the need for direct measurements on the same samples.

Findings

Relative per area respiration slightly increases with tree size.

Scaling exponents suggest deviation from constant respiration hypothesis.

Larger trees may have higher metabolically active tissue or nitrogen content.

Abstract

Respiration measurements of whole tree plants have been reported that give evidence that the relative per volume/mass unit respiration decreases with increase of tree body size. In this study, based on the available data published a question was explored if the relative per area unit respiration in trees can be a constant, independent of the surface area size. There is a definite gap in the published data when the allometric studies of tree body structure do not intercept with studies on trees respiration. Thus the question was studied with the help of indirect comparison between various data. The comparison showed that the scaling exponents, volume vs. surface area and respiration vs. stem volume, are slightly larger than they should be for the hypothesis of the relative respiration constancy to hold. The data studied give evidence that the relative per area unit respiration slightly increases with the increase in tree surface area. Possible explanations of the relationship include a different distribution of metabolically active parts of stem and higher nitrogen content in larger trees. Also, the published datasets might include large fast growing trees, which imply that larger trees grow faster and hence have higher per unit surface area growth respiration. A crucial experiment is required in which the respiration measurements were performed for the same data as the measurements of scaling between stem volume and surface area.