No, it is not true that there is a thick layer of humus in cold deserts. Humus is a component of soil formed from the decay of organic matter and is typically found in areas with substantial vegetation and organic material, such as forests and grasslands.
Cold deserts, characterized by low moisture levels, extreme temperature fluctuations, and sparse vegetation, do not support the accumulation of thick layers of humus. Instead, the soil in cold deserts is often poorly developed, with limited organic material and minimal horizons. The vegetation present in cold deserts is usually adapted to the arid conditions, resulting in low plant density and, consequently, reduced organic matter input to the soil. Therefore, rather than thick humus layers, cold deserts typically have thin, rocky, or sandy soils with some mineral content but very little organic matter.