Context-dependency of the impacts
The effect of the global changes did not vary across different habitat
types or organism body size classes for most of our analyses. The lack
of significance for body size was also highlighted when we analysed only
the four most abundant taxonomic groups (Acari, Collembola, nematodes,
and earthworms), which represent all three body size classes. The
patterns for nutrient enrichment were the most surprising, where
earthworms responded differently from the other three taxa. For the
other GCs, there were limited differences. However, looking at community
composition or functional and trophic groups instead of taxa or body
size groupings may tease apart other context-dependencies . For example,
previous work has shown various responses to environmental stressors and
GCs depending on the different functional types of earthworms .
In other analyses, community composition of soil microbial communities
were more affected than metrics of alpha- and beta-diversity to
different GCs. Incorporating such metrics of soil fauna communities may
be possible, especially in the case of nematodes and earthworms, as
communities are often reported at the level of functional types. In
addition, the biodiversity metrics used in this meta-analysis may not
have captured all the changes that occur to soil communities in invaded
ecosystems, resulting in the non-significant changes. For example,
established that soil communities responded more similarly within
trophic groups, and accounting for trophic group (and habitat type)
within the meta-analytic framework was needed to see the impact of
invasive species on soil fauna abundance.