J Plant Ecol ›› 2019, Vol. 12 ›› Issue (2): 281-291.DOI: 10.1093/jpe/rty021

• Research Articles • Previous Articles     Next Articles

Experimental evidence for root competition effects on community evenness in one of two phytometer species

Lina Weiss1,2,*, Linda Schalow1, Florian Jeltsch1,2,3 and Katja Geissler1   

  1. 1 Institute for Biochemistry and Biology, University of Potsdam, Am Mühlenberg 3, D-14476 Potsdam, Germany
    2 Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), D-14195 Berlin, Germany
    3 ZALF, Leibniz-Centre for Agricultural Landscape Research, Eberswalder Str. 84, D-15374 Müncheberg, Germany
    *Correspondence address. Institute for Biochemistry and Biology, University of Potsdam, Am Mühlenberg 3, D-14476 Potsdam, Germany. Tel: +49-331-977-6253; Fax: +49-331-977-1948; E-mail: weissl@uni-potsdam.de
  • Received:2017-05-17 Revised:2018-06-07 Accepted:2018-07-04 Online:2018-07-05 Published:2019-04-01



Plant–plant interactions, being positive or negative, are recognized to be key factors in structuring plant communities. However, it is thought that root competition may be less important than shoot competition due to greater size symmetry belowground. Because direct experimental tests on the importance of root competition are scarce, we aim at elucidating whether root competition may have direct or indirect effects on community structure. Indirect effects may occur by altering the overall size asymmetry of competition through root–shoot competitive interactions.


We used a phytometer approach to examine the effects of root, shoot and total competition intensity and importance on evenness of experimental plant communities. Thereby two different phytometer species, Festuca brevipila and Dianthus carthusianorum, were grown in small communities of six grassland species over three levels of light and water availability, interacting with neighbouring shoots, roots, both or not at all.

Important Findings

We found variation in community evenness to be best explained if root and shoot (but not total) competition were considered. However, the effects were species specific: in Dianthus communities increasing root competition increased plant community evenness, while in Festuca communities shoot competition was the driving force of this evenness response. Competition intensities were influenced by environmental conditions in Dianthus, but not in Festuca phytometer plants. While we found no evidence for root–shoot interactions for neither phytometer species root competition in Dianthus communities led to increased allocation to shoots, thereby increasing the potential ability to perform in size-asymmetric competition for light. Our experiment demonstrates the potential role of root competition in structuring plant communities.

Key words: plant–plant interactions, root and shoot competition, intensity vs. importance, experimental plant communities, asymmetry of competition