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Spatial complementarity in tree crowns explains overyielding in species mixtures


Deciphering the mechanisms that link biodiversity with ecosystem functions is critical to understanding the consequences of changes in biodiversity. The hypothesis that complementarity and selection effects drive relationships between biodiversity and ecosystem functions is well accepted, and an approach to statistically untangle the relative importance of these effects has been widely applied. In contrast, empirical demonstrations of the biological mechanisms that underlie these relationships remain rare. Here, on the basis of a field experiment with young trees, we provide evidence that one form of complementarity in plant communities—complementarity among crowns in canopy space—is a mechanism, related to light interception and use, that links biodiversity with ecosystem productivity. Stem biomass overyielding increased sharply in mixtures with greater crown complementarity. Inherent differences among species in crown architecture led to greater crown complementarity in functionally diverse species mixtures. Intraspecific variation, specifically neighbourhood-driven plasticity in crowns, further modified spatial complementarity and strengthened the positive relationship with overyielding—crown plasticity and inherent interspecific differences contributed near equally in explaining patterns of overyielding. We posit that crown complementarity is an important mechanism that may contribute to diversity-enhanced productivity in forests.

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Figure 1: Crown measurements and crown complementarity.
Figure 2: Functional dispersion of maximum growth rate and crown complementarity.
Figure 3: Crown complementarity and stem biomass overyielding.
Figure 4: Differences between three indices of crown complementarity and stem biomass overyielding.


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C. Tobner, S. Despoja, L. Nikinmaa, C. Archambault and numerous interns assisted with data collection. J. Cowles, D. Donoso, S. Gleason, S. Hobbie, W. Pearse, P. Wragg and A. Wright provided helpful comments. McGill University supported the project with land and facilities. The project was financially supported by the University of Minnesota (College of Biological Sciences, College of Food and Natural Resources, Institute on the Environment, and Graduate School), the National Sciences and Engineering Research Council of Canada, and an International Fulbright Science and Technology Award.

Author information




A.P., P.B.R. and C.M. designed the broader IDENT study. L.J.W. designed the crown complementarity study and its link to overyielding, with help from all authors. L.J.W. and A.P. collected data. L.J.W. analysed the data with assistance from P.B.R. and J.C.B., and wrote the first draft of the manuscript with editorial assistance from P.B.R. All authors contributed to further manuscript development.

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Correspondence to Laura J. Williams.

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The authors declare no competing financial interests.

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Supplementary Notes; Supplementary Methods; Supplementary Figures; Supplementary Tables (PDF 888 kb)

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Williams, L., Paquette, A., Cavender-Bares, J. et al. Spatial complementarity in tree crowns explains overyielding in species mixtures. Nat Ecol Evol 1, 0063 (2017).

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