Patterns of organic carbon and nitrogen stocks in soil particle-size fractions along an aridity gradient in Northern China’s deserts

•Organic C in < 100 μm soil particles accounted for 57.8 %-99.2 % of SOC in northern China’s drylands.•Organic C in < 100 μm soil particles and its contribution to SOC decreased with increasing aridity.•SOC in bulk soil was more associated with organic C in < 100 μm soil particles rather than with < 53 μm.•Organic C in < 100 μm soil particles and its contribution to SOC were more controlled by vegetation cover than MBC.