Data from: Extreme wetness reduces soil microbial residue carbon more substantially than extreme drought across grassland ecosystems

Soil microbial residue carbon (MRC) represents a significant component of
soil carbon pools and regulates the response of soil carbon sequestration
to precipitation changes. However, how soil MRC content responds to
extreme drought and wetness, and the underlying mechanisms in regional
grassland ecosystems, remains unclear. Here, we quantified the responses
of soil MRC content to extreme drought and wetness, and identified the key
drivers using a coordinated precipitation change experiment across nine
alpine and temperate grassland ecosystems in China. Extreme drought (-50%
precipitation) reduced MRC content by 8% on average. In contrast, extreme
wetness (+50% precipitation) unexpectedly caused a pronounced 24% average
decline in MRC content. Under extreme drought, reduced plant biomass
inhibited soil MRC formation, and soil microbial N enzymes accelerated
soil MRC decomposition. Moreover, wetter ecosystems exhibited greater
losses of soil MRC, while drier ecosystems experienced a more moderate
decline. Under extreme wetness, increased soil microbial N enzyme activity
accelerated the decomposition and utilization of microbial residue due to
intensified microbial nitrogen limitation, resulting in a reduction in
MRC. Our findings challenged the conventional understanding that extreme
wetness promotes MRC accumulation by revealing a stronger reduction in MRC
content under extreme wetness than under extreme drought. By uncovering
distinct mechanisms driving MRC responses to extreme drought and wetness,
our study provides critical insights into the dynamics of
microbial-derived carbon in grassland ecosystems under future climate
change.