2020 ESA Annual Meeting (August 3 - 6)

COS 13 Abstract - Metabolic scaling theory and cross-species relationships between canopy size, stem mitochondrial activity, and stem mass underlying a plant growth economics spectrum

Matiss Castorena1, Mark Earl Olson2, Brian Enquist1 and Tommaso Anfodillo3, (1)Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, (2)Universidad Nacional Autonoma de Mexico, Mexico City, DF, Mexico, (3)University of Padova, Legnaro, Italy
Background/Question/Methods

Size is a fundamental trait influencing plant form and function. Metabolic Scaling Theory (MST) predicts that body size is a central trait and that natural selection has optimized the scaling of vascular networks. As a result, numerous physiological processes and organismal traits covary with body size. MST predicts that this selective process has had consequences for the scaling of physiology, many fundamental traits, and life history variation. Intriguinly for plants, MST predicts that the net amount of carbon fixed by a given leaf area and the net ouput of metabolic power for a given tissue mass investment are independent of body size and similar across species. If correct, this constancy has the potential to explain variation in carbon allocation differences for growth and canopy-stem size proportions across species. However, empirical evidence supporting these predictions is critically missing. Here, we provide cross-species empirical evidence by sampling stem mass, stem volume, stem mitochondrial activity, and canopy size across 77 woody species. We sampled a wide range of plant lineages and wood densities, including gymnosperms and angiosperms, across a tropical rainforest, a tropical dry forest, and a temperate forest across Mexico.

Results/Conclusions

Cross-species relationships between canopy size and stem mitochondrial activity, stem mass and stem volume, stem mitochondrial activity per stem volume and tissue density, and canopy size per stem volume and tissue density are consistent with MST predictions. Additionally, stem mitochondrial activity and stem mass have a ¾-power law relationship whereas stem mitochondrial activity per stem mass and stem mass have a –¼-power law relationship. We discuss how these relationships ultimately reflect whole-plant economics rules in carbon gain and carbon investment for tissue production and maintenance across plants. We argue that these rules govern a growth carbon economics spectrum via a trade-off between fast growth and high tissue metabolic power. According to these rules, fast growing species have low density tissues, small canopies, and low metabolic rates whereas slow growing species have high density tissues, large canopies, and high metabolic rates for a given body volume.