Figure 1.

Soil organic matter age for two hypothetical soils with similar mean age but with different density functions. In both cases, the mean age is 200 years (purple vertical line), but for the exponentially distributed soil the 95% quantile Q ₉₅=599 years, while for the normally distributed soil (blue line) Q ₉₅=282 years. In asymmetric distributions with long tails such as the exponential or the phase type, the mean is more sensitive to the skewness than the median. In this example, the 50% quantile Q ₅₀=139 years (vertical solid red line) for the exponential distribution.