Trends of natural substitution of oak stands by mixed deciduous forest in forest steppe (stands in Tellerman experimental forest district, Institute of Forest Sciences, Russian Scademy of Sciences)

The paper objective is to prove the impossibility of obtaining oak stands in the course of natural regeneration on cuttings of deciduous stands in the forest steppe. Materials and Methods. In the forest steppe (Tellerman experimental forest district, Voronezh region) 10 forest stands, which grew after clear cuttings, were examined. The authors also examined the composition and structure of stand stories in natural upland oak stands of different age as well as the process of principal species renewal and indicators of their weakening. The composition and structure of upland naturally grown oak forest tiers of different ages, the renewal of principal species, and the indices of their weakening were studied. Results. The authors observed progressive processes of oak degradation and transformation of oak forests into mixed deciduous stands without any oak-trees. The causes of degradation include: droughts, underground water level decline, insect leaf damage, fungal diseases, forest mismanagement, and low competitiveness of light-loving oak in comparison with other shade-tolerant trees. It is proved that the ongoing transformation of oak forests into deciduous stands is irreversible and natural oak stand regeneration is impossible. In overripe stands, the first-tier oaks are mostly weakened, while ash and maple are rather strong. So, it is possible for these trees not only to replace oak in the first tier while it is dying off, but also to form ash and maple stands for an indefinitely long period of time. Conclusion. Natural regeneration of cutover stands without guaranteed artificial restoration of the English oak (Quercus robur) will result in decrease of stand commercial value, loss of valuable gene resources, and exhaustion of flora and fauna biodiversity in the ecosystems of entire regions. The only way to save the oak as a main forest-forming species of the region is its artificial propagation.