Soil microfauna mediate multifunctionality under multilevel warming in a primary forest

Soil microfauna play a crucial role in maintaining multiple functions
associated with soil phosphorous, nitrogen, and carbon cycling. Although
both soil microfauna diversity and multifunctionality are strongly
affected by climate warming, it remains unclear how their relationships
respond to different levels of warming. We conducted a 3-year
multilevel warming experiment with five warming treatments in a
subtropical primary forest. Using infrared heating systems, the soil
surface temperature in plots was maintained at 0.8 ℃, 1.5 ℃, 3.0 ℃, and
4.2 ℃ above ambient temperature (control, CK). Our findings indicate that
low-level (+0.8-1.5 ℃) warming increased soil multifunctionality,
nematode, and protist diversity compared to control, while high-level
(+4.2 ℃) warming significantly and negatively affected these variables. We
also identified significant positive correlations between soil
multifunctionality and nematode and protist diversity in the 0-10 cm soil
layer. Importantly, we found that soil multifunctionality and protist
diversity did not change significantly under temperatures 3.0 ℃ above
ambient. Our results imply that an increase of ~3 ℃ may represent
a critical threshold in subtropical forests, which is of great importance
for identifying response measures to global warming from the perspective
of microfauna in the surface soil. Our finding offers new evidence of the
role of soil microfauna in regulating multifunctionality with the
magnitude of warming in primary forests.