On the Tibetan Plateau, more efficient microbes did not mean more soil carbon
WHAT THE EVIDENCE SAYS
Large-scale soil sampling across a roughly 3,000-km Tibetan Plateau aridity gradient found microbial carbon-use efficiency increased with aridity even as soil organic carbon declined, producing a weak negative CUE–SOC relationship. The CUE increase was driven mainly by lower microbial respiration while growth changed little. Correlation, random-forest and structural-equation analyses linked SOC more strongly to physicochemical-protection indicators—including mineral-associated organic carbon, clay, calcium-bound carbon and microbial residue carbon—along with plant inputs and edaphic conditions.
WHY IT MATTERS / OUR READ
Soil carbon cannot be inferred from one appealing microbial efficiency metric. Across this gradient, whether carbon was physically and chemically stabilized mattered more than whether microbes retained a larger fraction of processed carbon. For land-carbon assessment and restoration, that argues for keeping mineral context, plant inputs and stabilization pools in the model rather than treating microbial efficiency as a universal shortcut.
CAVEATS / UNCERTAINTY
This is a spatial gradient study, not a manipulation that isolates causal pathways. Structural-equation and random-forest importance do not prove that any single stabilization mechanism caused the SOC pattern, and Tibetan Plateau soils and vegetation do not represent every dryland. Carbon-use-efficiency estimates are also method-dependent.
SOURCE
Global Change Biology — primary study
View original evidence ↗
Across a 3,000-km aridity gradient, microbial carbon-use efficiency increased as soil organic carbon declined; mineral association, clay, calcium-bound carbon and microbial residues tracked the carbon pattern more strongly.
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