Data extraction
Data, such as the control and treatment means, variances, and sampling
effort were extracted either from the text, tables, or figures using Web
Plot Digitizer (https://apps.automeris.io/wpd/). When data were
presented as a time-series, the last time point in the series was used
for the control and treatment means to maximise independence . When a
gradient of impacts was presented, e.g., different fertilizer levels,
the most extreme level was used as the treatment. Data were extracted at
the highest level of taxonomic resolution possible but above family
level (except enchytraeids, which are an important group commonly
reported only at family level). When presented as functional groups (as
is often seen in nematode and earthworm studies), the data were pooled
together into the taxonomic group.
Each study could provide more than one comparison between a control and
treatment, henceforth referred to as a ‘case’. Most commonly, primary
papers presented data for multiple biodiversity metrics (for example,
abundance, biomass and species richness), different taxonomic groups,
different GCs or environmental stressors, or from different habitat
types. Each was extracted as an individual case. Where a paper presented
multiple GCs/environmental stressors, each was extracted independently
from any other.