Fig.
1. Ombrothermic diagram of (A) air temperature at 2 m above the ground
(continuous red line) and precipitation (dashed blue line) and (B) soil
temperature (continuous red line) and soil moisture (dashed blue line)
at 8 cm below the ground in 2021 and January 2022. The blue vertical
stripes in June and September indicate the two mowing periods (14-25.06
and 13-24.09). Data source: local climatic station in the Jena
Experiment.
Following a gradient in soil characteristics, the experiment was set up
in four blocks containing an equal number of plots per plant diversity
treatment within each block to avoid any confounding effects of soil
heterogeneity. In total, the study site consists of 80 plots
(~5.5 m × 6 m) that differ in levels of sown plant
species richness (1, 2, 4, 8, 16, 60 species) and plant functional group
richness (one to four of the functional group: grasses, small herbs,
tall herbs, legumes). Following common management practices in temperate
extensively-used grasslands in Central Europe, where the Jena Experiment
is located, the experiment was mowed twice. Moreover, the experimental
plots were weeded three times during the study period to maintain the
plot’s target species composition.
Temporal above- and belowground
sampling
We sampled aboveground and belowground biological response variables
biweekly (or every three weeks during winter). Even though the
measurements’ definitions differ, e.g., plant community height would be
better defined as a biological feature, and detritivore feeding activity
is an activity rate, each measured response variable is commonly related
to an ecological process (Table 1). We also present a simplified
description of the sampling methods for each process. Please see the
Supplemental Material for an extended version of the methods.