Root chemistry and soil fauna, but not soil abiotic conditions explain the effects of plant diversity on root decomposition

Abstract

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.

Effects of elevated CO2, increased nitrogen deposition, and plant diversity on aboveground litter and root decomposition

“…In contrast to the increasing aboveground litter decomposition, our results also support the finding that a decrease in root N content with increasing richness may slow the root decomposition (Chen et al. , b). This can be interpreted by the fact that although the increasing plant richness decreases the initial N and lignin contents of root, the effect of N content change on root decomposition is the higher than the lignin contents, which leads the net effect of increasing plant richness on the root decomposition and N release is negative.…”

“…Single species plots had the higher tissue N and lignin contents both above‐ and belowground, which supports the finding that the tissue N content decreases with increasing species richness (Chen et al. , b). Plot level tissue quality changes were mainly dependent on the species tissue quality in pant community.…”

“…, Chen et al. , b), which is in contrast to several other studies that plant diversity has the much smaller effects on decomposition (Hector et al. , Knops et al.…”

“…, Chen et al. , b). However, the final best SEM showed that global change factors did not affect the decomposition of litter and root via changes in changes in vegetation and soil.…”

Root Decomposition of Grazed Signalgrass in Response to Stocking and Nitrogen Fertilization Rates

“…After determining lignin and N concentrations, we estimated the lignin/N ratio. Previous studies indicated that the lignin/N ratio was a good predictor of litter decomposition rate (Zhang et al, 2008; Chen et al, 2017). Root litter N was estimated by multiplying root N concentration by the residual root biomass within each litter bag.…”