Disturbances of Soil Cover in Natural Ecosystems.

In natural ecosystems soil (Sihote-Alihe) is being disturbed by the outcasts of moles, gophers, marmots and foxes, borrows by wildboars and tigers, tree windthrows, activity of invertebrates and erosion. The upper layer of soil can be totally mixed up by invertebrates, wildboars and tigers. The matter from deep soil layers can be exposed to the surface. Natural recovery of the soil cover varies in different ecosystems. Generations of trees are changed in a natural forest through windtrows or windbreaks, which also cause disturbance of soil. The next generation of trees is able to restore a soil pattern typical for this forest in 50-150 years. After stop of the human activity disturbed podzolic soils (mixed boreal forests) may return to the initial state in 200 years. If E horizon has been totally lost the restoration may result in formation of non-differentiated acid (brown) soils. After stop of plowing the arable layer of podzolic soils differentiates into two subhorizons A and AE. Such AE may persist in forest ecosystems for 150 years. Over 200 years it evolves into the typical Å horizon. Small-scale natural disturbances affecting topography (burrows of small vertebrates, raised part around the tree bole and depressed patches between trees disappear in 20-150 years. Evidences of greater disturbances such as windtrows may be preserved in soils for 500 years and more. Thus, recovery of soils may take place during 20-1000 years and more depending on scale of disturbance. Deep humus soils are unable to completely restore their profile without external intervention. In them the humus layer will never exceed 30 cm. In conditions of the anthroposphere, arable soils may recover their natural profile after 50-200 years after being abandoned and converted into fallow lands. Technologically disturbed soils may form only shallow humus soils with a sod during 15 years and more.