Mapping soil microbial residence time at the global scale

Soil microbes ultimately drive the mineralization of soil organic carbon
and thus ecosystem functions. We compiled a dataset of the seasonality of
microbial biomass carbon (MBC) and developed a semi-mechanistic model to
map monthly MBC across the globe. MBC exhibits an equatorially symmetric
seasonality between the Northern and Southern Hemispheres. In the Northern
Hemisphere, MBC peaks in autumn and is minimal in spring at low latitudes
(<25° N), peaks in the spring and is minimal in autumn at
mid-latitudes (25°-50° N), while peaks in autumn and is minimal in spring
at high latitudes (>50° N). This latitudinal shift of MBC
seasonality is attributed to an interaction of soil temperature, soil
moisture, and substrate availability. The MBC seasonality is inconsistent
with patterns of heterotrophic respiration, indicating that MBC as a proxy
for microbial activity is inappropriate at this resolution. This study
highlights the need to explicitly represent microbial physiology in
microbial models. The interactive controls of environments and substrate
on microbial seasonality provide insights for better representing
microbial mechanisms in simulating ecosystem functions at the seasonal
scale.