Amino acid fingerprint of a grassland soil reflects changes in plant species richness

Abstract

A positive plant diversity to plant aboveground productivity relation has been shown to alter carbon and nitrogen fluxes in soils. Thus, most investigations focussed on the C-and N-input via litter fall, widely neglecting the importance of root exudation. As microbes, which are known to be important drivers of matter fluxes in soil, feed on these root exudates, increased knowledge on the availability of these compounds in soil might help to understand biodiversity effects on soil. We therefore investigated the effect of plant diversity on size and composition of the free soil amino acid pool in a grassland experiment, as amino acids are an important C-as well as N-source for microbes. Despite a positive diversity effect on plant productivity, we only found an insignificant increase of the size of the free amino acid pool in soil. This was most likely caused by an increase of the microbial population and thus an increased amino acid mineralization. At the same time the composition of the amino acid pool changed significantly between plant diversity levels. This most likely reflects differences in plant input as well as differences in microbial mineralization and enabled us to separate diversity levels by means of discriminant analysis.

Foliar and soil δ15N values reveal increased nitrogen partitioning among species in diverse grassland communities

“…Lolium perenne is known to prefer inorganic N compared with organic N, although it is capable to take up organic N compounds (Weigelt et al 2003(Weigelt et al , 2005. The uptake of organic N forms by plants is of minor importance at our experimental site as it has been shown that the availability of dissolved organic nitrogen such as free amino acids is rather low (Oelmann et al 2007;Sauheitl et al 2010), and microbes are probably the better competitors for organic N sources. Bailey (1998) found that L. perenne absorbed both mineral N forms at equal rates under stress, for example, after defoliation, which was interpreted as a maximization of N acquisition because N uptake was not restricted by a particular N form.…”

Explaining the variation in the soil microbial community: do vegetation composition and soil chemistry explain the same or different parts of the microbial variation?

“…The impacts of plant composition on below-ground communities are generally attributed to species differences in litter quality, root exudates, herbivory and nutrient uptake (Hobbie 1992). Plant species are known to vary in the quality and quantity of carbon types released in their litter and root exudates (Langley and Hungate 2003;Sauheitl et al 2010). Thus plants may directly impact root-associated soil organisms through resources produced by the roots (root exudates) (Paterson 2003) and the decomposer food web by determining the quantity and quality of litter that enters the soil (Keith et al 2009).…”

Differential responses of soil bacteria, fungi, archaea and protists to plant species richness and plant functional group identity

“…Increasing plant species richness has generally been shown to lead to increased soil microbial biomass (Eisenhauer et al., ; Scherber et al., ; Zak, Holmes, White, Peacock, & Tilman, ) and activity (Eisenhauer et al., ). One explanation is that increased plant species richness diversifies the resource pool so that the biomass of a larger variety of soil microbes may be sustained (Milcu, Partsch, Langel, & Scheu, ; Sauheitl, Glaser, Dippold, Leiber, & Weigelt, ). Another possibility is that increasing plant species richness enhances the amount of primary production, which in turn may increase the biomass of soil fungi and bacteria (De Deyn, Quirk, & Bardgett, ).…”