Higher plant diversity reduces nitrate leaching by complementary resource use, while its relation to leaching of other N species is unclear. We determined the effects of plant species richness, functional group richness, and the presence of speciﬁc functional groups on ammonium, dissolved organic N (DON), and total dissolved N (TDN) leaching from grassland in the ﬁrst 4 years after conversion from fertilized arable land to unfertilized grassland. On 62 experimental plots in Jena, Germany, with 1-60 plant species and 1-4 functional groups (legumes, grasses, tall herbs, small herbs), nitrate, ammonium, and TDN concentrations in soil solution (0-0.3 m soil layer) were measured fortnightly during 4 years. DON concentrations were calculated by subtracting inorganic N from TDN. Nitrogen concentrations were multiplied with modeled downward water ﬂuxes to obtain N leaching. DON leaching contributed most to TDN leaching (64 ± SD 4% of TDN). Ammonium leaching was unaffected by plant diversity. Increasing species richness decreased DON leaching in the fourth year. We attribute this ﬁnding to enhanced use of DON as a C and N source and enhanced mineralization of DON by soil microorganisms. An increase of species richness decreased TDN leaching likely driven by the complementary use of nitrate by diverse mixtures. Legumes increased DON and TDN leaching likely because of their N-ﬁxing ability and higher litter production. Grasses decreased TDN leaching because of more exhaustive use of nitrate and water. Our results demonstrate that increasing plant species richness decreases leaching of DON and TDN.
Leimer, S., Roscher, C., Wilcke, W., Oelmann, Y., Scheu, S., Eisenhauer, N., Weigelt, A., Milcu, A. and Wirth, C. (2016), Mechanisms behind plant diversity effects on inorganic and organic N leaching from temperate grassland. doi: 10.1007/s10533-016-0283-8
Sophia Leimer s
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