Genesis of brown forest soils in the north of Amur region and Sakhalin

The specificity of raw-humus brown forest soils (burozems) in the eastern part of their area is caused by local peculiarities of the geomorphic, lithological, and climatic conditions. These soils are developed from pebbly loamy products of long-term weathering of Mesozoic rocks. The activity of tectonic and slope processes under conditions of the monsoon type of climate with heavy summer rainfalls dictates the instability of the surface mantle of loose rocks and the continuous rejuvenation derivatives of the solid soil phase; the soil profiles are immature. It can be supposed that the raw-humus burozems in this region represent the prepodzolic stage of soil formation. The development of podzolic soils proper is hampered by the regular rejuvenation of the soil material. Under secondary deciduous forests with herbs in the ground cover, the raw-humus horizons are replaced by mull-humus horizons. According to the new Russian soil classification system [9], these soils should be placed into the group of burozems. However, the properties of the humus horizon of these soils and their mineral mass make it possible to consider them as rather specific intergrade formations.