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Background and aims Soil aggregate stability depends
on plant community properties, such as functional
group composition, diversity and biomass production.
However, little is known about the relative importance
of these drivers and the role of soil organisms in
mediating plant community effects.
Methods We studied soil aggregate stability in an experimental grassland plant diversity gradient and considered several explanatory variables to mechanistically explain effects of plant diversity and plant functional
group composition. Three soil aggregate stability measures
(slaking, mechanical breakdown and microcracking)
were considered in path analyses.
Results Soil aggregate stability increased significantly
from monocultures to plant species mixtures
and in the presence of grasses, while it decreased
in the presence of legumes, though effects differed
somewhat between soil aggregate stability measures.
Using path analysis plant community effects
could be explained by variations in root biomass,
soil microbial biomass, soil organic carbon concentrations
(all positive relationships), and earthworm
biomass (negative relationship with mechanical
breakdown).
Conclusions The present study identified important
drivers of plant community effects on soil aggregate
stability. The effects of root biomass, soil microbial
biomass, and soil organic carbon concentrations were
largely consistent across plant diversity levels suggesting that the mechanisms identified are of general relevance.
