Water availability rather than temperature control soil fauna community structure and prey-predator interactions

The ongoing climate change may strongly impact soil biodiversity with
cascading effects on the processes they drive. Thus, it is of prime
interest to improve our knowledge about responses by soil organisms such
as collembolans to expected shifts in environmental conditions by
considering communities comprising both detritivores and predators. The
aim of the present study was to evaluate how simulated climate change and
predation under laboratory conditions alter a collembolan community. To
infer the impact of climate change, we applied a decreased level of soil
moisture (60% vs. 30% soil water holding capacity) and an increasing air
temperature (15 °C vs. 25 °C) to a collembolan community constituted by
four species (Folsomia candida, Protaphorura fimata, Proisotoma minuta and
Mesaphorura macrochaeta) exhibiting distinct functional traits, e.g. body
size and furca presence, in presence or absence of a predatory gamasid
Acari (Stratiolaelaps scimitus) during two months in a microcosm
experiment. We observed that decreasing soil moisture altered the
collembolan community with species-specific responses. Interaction between
soil moisture, temperature and predation indicates that low soil moisture
reduced total collembolan abundance especially i) by suppressing the
positive effect of increasing temperature and ii) by increasing the
predatory control on collembolan abundance. These results highlight that
soil moisture is the major driver of Collembola community and by
consequence, a shift in climatic parameters with the ongoing climate
change should strongly modify the Collembola community structure and the
predator-prey interaction. Our findings are highly important since a
strengthening of predation impact on Collembola prey could have major
consequences on the whole soil food web being able to lead to a slowdown
of key ecosystem processes they drive (e.g., litter decomposition and
nutrient recycling). Finally, our study promotes the need to study more
complex systems considering distinct soil-dwelling species, their
functional traits and their trophic interactions to better predict the
ecosystem responses to the ongoing climate change.