Long term effects of plant diversity and composition on plant stoichiometry

Jordan Guiz1, Helmut Hillebrand1, Maike Abbas1, Elizabeth Borer2
1 University of Oldenburg
2 University of Minnesota

O 5.5 in Linking biodiversity and biogeochemistry

15.07.2014, 12:20-12:40, H19

Plant elemental composition is an important indicator of resource limitation and determines the nutritional quality of plant material for herbivores. Very few studies tested whether (and how) plant stoichiometry is affected by plant diversity and composition. In two long-term experimental manipulations of plant biodiversity (Jena and Cedar Creek), we tested whether plant richness (species and functional groups) and composition (proportions of functional groups) affects the trends of community-wide C:N stoichiometry and its temporal variability over a decade-long sampling period.

In Jena, the community C:N was globally increasing over time and this trend was stronger with increasing richness. The temporal variability of C:N showed an opposite pattern and decreased as richness increased. At Cedar Creek, richness had the opposite effect on both C:N trends and temporal variability which respectively decreased and increased with the number of species or functional groups in the community.

The community compositions showed comparable trends to C:N over time in both sites. In Jena, the replacement of legumes by forbs was faster with increasing richness, thus explaining C:N trends as the former exhibit lower C:N than the latter. At Cedar Creek, the responses of C:N at high richness levels correspond to the replacement of C4 grass, which have higher and narrower C:N values, by forbs.

In this study, the effect of species and functional richness on the trends and temporal variability of C:N appeared to be mediated by a modification of the functional group proportions over time. In both sites, forbs seemed to have a competitive advantage at high richness levels, thus influencing the community C:N because of their differences with other functional groups in term of C:N mean values and variances.

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last modified 2014-04-02