x = Organic C content in soil (in g Carbon/kg)
y = Clay content (in g/kg)

Data taken from 150 forest plots. Plots with missing data were excluded.

The clay content in a soil is one determinant of how much carbon can be accumulated in a soil.

Reference:
Solly et al (2014). Factors controlling decomposition rates of fine root litter in temperate forests and grasslands. Plant and Soil, 382(1-2), 203-218.

y --> x