A global map of microbial residence time

Soil microbes are the fundamental engine for carbon (C) cycling. Microbial
residence time (MRT) therefore determines the mineralization of soil
organic C, releasing C as heterotrophic respiration and contributing
substantially to the C efflux in terrestrial ecosystems. We took use of a
comprehensive dataset (2627 data points) and calculated the MRT based on
the basal respiration and microbial biomass C. Large variations in MRT
were found among biomes, with the largest MRT in boreal forests and
grasslands and smallest in natural wetlands. Biogeographic patterns of MRT
were found along climate (temperature and precipitation), vegetation
variables (root C density and net primary productivity), and edaphic
factors (soil texture, pH, topsoil porosity, soil C, and total nitrogen).
Among environmental factors, edaphic properties dominate the MRT
variations. We further mapped the MRT at the global scale with an
empirical model. The simulated and observed MRT were highly consistent at
plot‐ (R2=0.86), site‐ (R2=0.88), and biome‐ (R2=0.99) levels. The global
average of MRT was estimated to be 38 (±5) days. A clear latitudinal
biogeographic pattern was found for MRT with lower values in tropical
regions and higher values in the Arctic. The biome‐ and global‐level
estimates of MRT serve as valuable data for parameterizing and
benchmarking microbial models.