N2 fixation and performance of 12 legume species in a 6-year grassland biodiversity experiment
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- Roscher, C., Thein, S., Weigelt, A. et al. Plant Soil (2011) 341: 333. doi:10.1007/s11104-010-0647-0
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Highly variable effects of legumes have been observed in biodiversity experiments, but little is known about plant diversity effects on N2 fixation of legume species. We used the 15N natural abundance method in a non-fertilized regularly mown 6-year biodiversity experiment (Jena Experiment) to quantify N2 fixation of 12 legume species. The proportion of legume N derived from the atmosphere (%Ndfa) differed significantly among legume species. %Ndfa values were lower in 2004 after setting-up the experiment (73 ± 20) than in the later years (2006: 80 ± 16; 2008: 78 ± 12). Increasing species richness had positive effects on %Ndfa in 2004 and 2006, but not in 2008. High biomass production of legumes in 2004 and 2006 declined to lower levels in 2008. In 2006, legume positioning within the canopy best explained variation in %Ndfa values indicating a lower reliance of tall legumes on N2 fixation. In 2008, larger %Ndfa values of legumes were related to lower leaf P concentrations suggesting that the availability of phosphorus limited growth of legumes. In summary, diversity effects on N2 fixation depend on legume species identity, their ability to compete for soil nutrients and light and may vary temporally in response to changing resource availability.