Humus content and second humus horizons in gray forest soils of the Vladimirskoe opol'e region (Russia)

More than 900 samples of gray forest soils were analyzed. In the profile of soils possessing the second humus horizon (SHH), the highest carbon conten t (3.0%) was found in the plow layer. Upper layers of SHHs may contain up t o 4.6% of carbon. This phenomenon, along with the weakly manifested microto pography of the soil surface and the gradual change in the SHH depth, makes it possible to conclude that the role of microtopography in the genesis of soils with the SHH is generally overestimated. The SHH may be considered t he lower part of the integral natural humus-accumulative layer that has not been affected by tillage.