Abstract
Biodiversity is well known to enhance many ecosystem functions, but empirical evidence for the role of soil biodiversity for plant biomass production and allocation is scarce. Here we studied the effects of animal decomposer diversity (1, 2, and 4 species as well as a control without any decomposers) on the biomass production and aboveground-belowground biomass allocation of common wheat using two earthworm and two Collembola species using an additive design in two soil management types (organic and mineral fertilizer treatments) in a microcosm experiment. Shoot (+11%), spike (+7%), and root biomass (+56%), increased significantly with increasing decomposer diversity, and these effects were consistent across the two soil management types. Notably, decomposer diversity effects were stronger on root than on shoot biomass, significantly decreasing the shoot-to-root ratio (−27%). Increased plant biomass production was positively correlated with a decomposer richness-induced increase in soil water nitrate concentrations five weeks after the start of the experiment. However, elevated soil nitrate concentrations did not cause significantly higher plant tissue nitrogen concentrations and nitrogen amounts, suggesting that additional mechanisms might be at play. Consistent decomposer diversity effects across soil management types indicate that maintaining soil biodiversity is a robust and sustainable strategy to enhance crop yield.
Highlights
Many studies have investigated the relationship between biodiversity and ecosystem functioning[1,2,3] as well as the implications for the provisioning of ecosystem services[4,5]
In order to explore potential mechanisms of decomposer species richness effects on plant growth, relationships between ammonium as well as nitrate concentrations in soil solution and plant biomass were investigated. These analyses showed that plant biomass was significantly positively correlated with nitrate concentrations in soil water five weeks after the start of the experiment (Fig. 2A–C; Table 2)
We found consistent decomposer diversity effects on plant growth across soil management types, which most likely were mediated in part by elevated nutrient mineralization rates at high decomposer diversity
Summary
Many studies have investigated the relationship between biodiversity and ecosystem functioning[1,2,3] as well as the implications for the provisioning of ecosystem services[4,5]. Both of these bottom-up and top-down effects are affected by soil biodiversity[16,17] Detritivores, such as earthworms and Collembola, drive nutrient mineralization processes by influencing the community composition and activity of soil microorganisms[21,22] and plant antagonists by grazing and changes in soil conditions[23]. Effects of enhanced nutrient mineralization by decomposers may be superimposed by the addition of mineral fertilizers[34], which is common practice in many agricultural fields, if they are conventionally managed Such potential context-dependencies of decomposer diversity effects have rarely been tested far. We expected (1) decomposer diversity to enhance plant growth, but (2) decomposer diversity effects to be more pronounced in the organic soil than in the soil with mineral fertilizer
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