Effects of Elevated [CO2] and N Fertilization on Interspecific Interactions in Temperate Grassland Model Ecosystems
Interspecific differences in the response to e[CO2] were stronger in the mixed sward (−2 % for L. perenne and +65 % for T. repens) than in the pure swards (+13 % for L. perenne and +19 % for T. repens), demonstrating that e[CO2] does affect not only the yield, but also the interspecific interactions and the species composition of mixed plant communities. Thus, studying the ecosystem response to e[CO2] needs experiments with mixed plant communities.
RY and RNY <0.5 for T. repens provides evidence that T. repens was adversely affected from competition with the grass, while the grass competed more successfully for resources (RY >0.5) or even clearly gained from synergistic effects (RY >1.0).
The extreme resource complementarity (RNYT of up to 1.9) at low N and the loss of resource complementarity (RYT and RNYT close to 1.0) at high N demonstrate that mineral N availability was the most important limiting factor for plant growth and interspecific interactions in the low N treatment of the Swiss FACE experiment. Thus, this FACE experiment with grasses and legumes provides a good tool to study effects of e[CO2] on the N cycle of grassland ecosystems under strongly limiting and non-limiting N availability.
KeywordsWhite Clover Relative Yield Perennial Ryegrass Interspecific Interaction Lolium Perenne
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