Root chemistry and soil fauna, but not soil abiotic conditions explain the effects of plant diversity on root decomposition
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Plant diversity influences many ecosystem functions including root decomposition. However, due to the presence of multiple pathways via which plant diversity may affect root decomposition, our mechanistic understanding of their relationships is limited. In a grassland biodiversity experiment, we simultaneously assessed the effects of three pathways—root litter quality, soil biota, and soil abiotic conditions—on the relationships between plant diversity (in terms of species richness and the presence/absence of grasses and legumes) and root decomposition using structural equation modeling. Our final structural equation model explained 70% of the variation in root mass loss. However, different measures of plant diversity included in our model operated via different pathways to alter root mass loss. Plant species richness had a negative effect on root mass loss. This was partially due to increased Oribatida abundance, but was weakened by enhanced root potassium (K) concentration in more diverse mixtures. Equally, grass presence negatively affected root mass loss. This effect of grasses was mostly mediated via increased root lignin concentration and supported via increased Oribatida abundance and decreased root K concentration. In contrast, legume presence showed a net positive effect on root mass loss via decreased root lignin concentration and increased root magnesium concentration, both of which led to enhanced root mass loss. Overall, the different measures of plant diversity had contrasting effects on root decomposition. Furthermore, we found that root chemistry and soil biota but not root morphology or soil abiotic conditions mediated these effects of plant diversity on root decomposition.
KeywordsSpecies richness Functional groups Root litter Jena Experiment SEM
The Jena Experiment was funded by the German Science Foundation (DFG, FOR 1451) and was supported by the Friedrich-Schiller-University Jena and the Max Planck Society. We thank the gardeners of the Jena Experiment for maintaining the plots and student helpers for the field work and sample preparation.
Root mass loss, root C:N ratio, and soil water content are deposited at the Jena Experiment database and will be accessible via Dryad Digital Repository http://dx.doi.org/10.5061/dryad.6k23f (Chen et al. 2017). The rest of the data are deposited at the Jena Experiment database and will be deposited at Pangaea (http://www.pangaea.de).
Author contribution statement
LM, JR, AG, MSL, and AW designed the experiment. HC, CF, OGM, NH, and ML collected the data. HC analyzed the data and wrote the manuscript with input from KB and AW. All authors provided input on the final written manuscript.
Compliance with ethical standards
The Jena Experiment was funded by the German Science Foundation (DFG, FOR 1451). LM was funded by the Netherlands Organisation for Scientific Research (NWO, Vidi Grant 864.14.006). MSL was funded by the DFG (Gl262/14 and Gl262/19). YO was funded by the DFG (Oe516/3-2), WW was funded by the DFG (Wi1601/4) and the Swiss National Science Foundation (SNF, 200021E-131195/1).
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable institutional and/or national guidelines for the care and use of animals were followed.
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