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A general integrative model for scaling plant growth, carbon flux, and functional trait spectra


Linking functional traits to plant growth is critical for scaling attributes of organisms to the dynamics of ecosystems1,2 and for understanding how selection shapes integrated botanical phenotypes3. However, a general mechanistic theory showing how traits specifically influence carbon and biomass flux within and across plants is needed. Building on foundational work on relative growth rate4,5,6, recent work on functional trait spectra7,8,9, and metabolic scaling theory10,11, here we derive a generalized trait-based model of plant growth. In agreement with a wide variety of empirical data, our model uniquely predicts how key functional traits interact to regulate variation in relative growth rate, the allometric growth normalizations for both angiosperms and gymnosperms, and the quantitative form of several functional trait spectra relationships. The model also provides a general quantitative framework to incorporate additional leaf-level trait scaling relationships7,8 and hence to unite functional trait spectra with theories of relative growth rate, and metabolic scaling. We apply the model to calculate carbon use efficiency. This often ignored trait, which may influence variation in relative growth rate, appears to vary directionally across geographic gradients. Together, our results show how both quantitative plant traits and the geometry of vascular transport networks can be merged into a common scaling theory. Our model provides a framework for predicting not only how traits covary within an integrated allometric phenotype but also how trait variation mechanistically influences plant growth and carbon flux within and across diverse ecosystems.

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Figure 1: Using plant traits to predict allometric growth for gymnosperms and angiosperms.
Figure 2: Using plant traits to predict individual growth rates.
Figure 3: Using plant traits and growth rate to predict carbon use efficiency and FTS.

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We especially thank J. Stegen for assistance with data and comments. We also thank S. R. Saleska, T. Huxman, A. Angert, A. E. B. Arnold, J. Pither, C. Lamanna and P. Chesson for comments and suggestions on earlier drafts. I. J. Wright provided constructive comments. B.J.E., A.J.K., C.A.P. and N.G.S. were supported by a NSF Career Award (to B.J.E.). A.J.K. was also supported by an HHMI Undergraduate Science Education Program Award to Kenyon College and N.G.S. was supported by a USGS fellowship. M.C.M. and S.C.S. were supported by an NSF predoctoral award. I. J. Wright and M. Pickup shared data sets. In addition, we acknowledge the use of GLOPNET data in some of our analyses.

Author Contributions B.J.E. designed the study. B.J.E., A.J.K. and S.C.S. developed the theory, compiled and analysed data, and wrote the paper. N.G.S., M.C.M. and C.A.P. provided data, ideas and comments on manuscript drafts.

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Supplementary Information

This file contains Supplementary Discussion and Equations, Supplementary Methods, Supplementary Figures S1-S4 (Graphs), Supplementary Tables S1-S2 and additional references. (PDF 7730 kb)

Supplementary Data

This file contains the original data which supports Supplementary Table S1 in file s1. Please note that this file was originally omitted and was uploaded on April 2nd, 2009. (XLS 194 kb)

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Enquist, B., Kerkhoff, A., Stark, S. et al. A general integrative model for scaling plant growth, carbon flux, and functional trait spectra. Nature 449, 218–222 (2007).

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