Abstract
Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e. though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-to-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-to-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs.
Highlights
Variable Shoot biomass Root biomass Shannon diversity roots Root complementarity effect Root selection effect Root net biodiversity effect Exudate richness Exudate amount Bacterial biomass Fungal biomass Fungi: bacteria
Species-specific root biomass was determined via quantitative PCR, and the diversity and quantity of root exudates were assessed via high pressure liquid chromatography (HPLC)
We identified a total of 15 plant-derived compounds, i.e., fumaric acid, chlorogenic acid, 4-hydroxybenzoic acid, vanillic acid, syringic acid, 4-hydroxybenzaldehyde, vanillin, polydatin, p-coumaric acid, t-2-methoxycinnamic acid, phenylacetic acid, coumarin, a flavone-type compound, 2 quercetin glycoside derivatives, and a benzoate ester
Summary
Variable Shoot biomass Root biomass Shannon diversity roots Root complementarity effect Root selection effect Root net biodiversity effect Exudate richness Exudate amount (log10) Bacterial biomass Fungal biomass Fungi: bacteria. Using a 13C labelling approach, Lange et al.[6] provided experimental evidence for the significant role of root exudates in fuelling soil microorganisms. They showed that plant diversity increases the transfer of 13C from plants to soil microbial fatty acids. Sauheitl et al.[27] found that the composition, but not the amount, of amino acids changed along a plant diversity gradient It remains unclear if soil microbial communities depend on plant diversity-driven variations in root biomass and composition[28], root diversity[29], quantity and diversity of root exudates[6,26], or their combination. Species-specific root biomass was determined via quantitative PCR, and the diversity and quantity of root exudates were assessed via high pressure liquid chromatography (HPLC)
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