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Individual variability and mortality required for constant final yield in simulated plant populations

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Abstract

When plant monocultures are sown over a wide range of densities for a given period of time, the total biomass yield increases with density at low densities and then levels off at high densities, a phenomenon called constant final yield (CFY). There are several reported cases, however, where the total yield decreases at very high densities, but the reasons for such exceptions are not known. We used a spatially explicit, individual-based “field of neighborhood” simulation model to investigate the potential roles of spatial pattern, individual variation, and competitive stress tolerance for CFY. In the model, individual plants compete asymmetrically for light when their fields overlap, and this competition decreases growth and increases mortality. We varied (1) the initial size variation, (2) the spatial pattern, and (3) ability to survive intense competition and examined the effects on the density-biomass relationship. CFY was always observed when there was high variability among individuals, but not always when variability was low. This high size variation could be the result of high initial size variability or variation in the degree of local crowding. For very different reasons, very high and very low tolerance for competition resulted in decreasing total biomass at very high densities. Our results emphasize the importance of individual variation for population processes and suggest that we should look for exceptions to CFY in homogeneous, even-aged, regularly spaced populations such as plantations.

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Acknowledgement

The study was supported by the grant GACR 13-17118S from the Grant Agency of the Czech Republic and the University of Copenhagen Program of Excellence. Access to computing and storage facilities owned by parties and projects contributing to the National Grid Infrastructure MetaCentrum provided under the program “Projects of Large Infrastructure for Research, Development, and Innovations” (LM2010005) is much appreciated.

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Authors and Affiliations

  1. Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 31, 370 05, České Budějovice, Czech Republic

    Pavel Fibich & Jan Lepš

  2. Institute of Entomology, Biology Center of the Academy of Sciences of the Czech Republic, Branišovská 31, 370 05, České Budějovice, Czech Republic

    Jan Lepš

  3. Department of Plant and Environmental Sciences, University of Copenhagen, Rolighedsvej 21, DK-1958, Frederiksberg, Denmark

    Jacob Weiner

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  1. Pavel Fibich
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  2. Jan Lepš
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Correspondence to Pavel Fibich.

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Fibich, P., Lepš, J. & Weiner, J. Individual variability and mortality required for constant final yield in simulated plant populations. Theor Ecol 7, 263–271 (2014). https://doi.org/10.1007/s12080-014-0216-x

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