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Abstract

1. Land‐use intensification drives changes in microbial communities and the soil
functions they regulate, but the mechanisms underlying these changes are poorly
understood as land use can affect soil communities both directly (e.g. via changes
in soil fertility) and indirectly (e.g. via changes in plant inputs).
2. The speed of microbial responses is also poorly understood. For instance, whether
it is long‐term legacies or short‐term changes in land‐use intensity that drive
changes in microbial communities.
3. To address these topics, we measured multiple microbial functions, bacterial and
fungal biomass and abiotic soil properties at two time intervals 3 years apart. This
was performed in 150 grassland sites differing greatly in management intensity
across three German regions.
4. Observed changes in microbial soil properties were related to both long‐term means
and short‐term changes in: abiotic soil properties, land‐use intensity, community
abundance‐weighted means of plant functional traits and plant biomass properties
in regression and structural equation models. Plant traits, particularly leaf phosphorus,
and soil pH were the best predictors of change in soil microbial function, as well
as fungal and bacterial biomass, while land‐use intensity showed weaker effects.
5. Indirect legacy effects, in which microbial change was explained by the effects
of long‐term land‐use intensity on plant traits, were important, thus indicating a
time lag between plant community and microbial change. Whenever the effects of
short‐term changes in land‐use intensity were present, they acted directly on soil
microorganisms.