Influence of tree growth density and illumination on natural regeneration in protective forest belt of the Lugansk People's Republic

The paper presents the results of studying the renewal of the main forest-forming species in the field-protecting forest belts of the State Unitary Enterprise of the Lugansk People's Republic "Agrofond", which is located in the Artemovskiy district of the city of Lugansk. The purpose of the work is to assess the condition of the undergrowth of woody and shrubby vegetation in the field-protecting forest belts and to identify the factors affecting its development. The study used the methodology used in forest taxation and the methodology of systemic studies of forest-agricultural landscapes. The soil moisture was determined using the thermostatic-weight method. The litter was collected from five litter catchers, which were placed in the forest belt in a random order. The quantitative and qualitative composition of the undergrowth in the field-protecting forest belts was studied using circular counting plots with an area of 10 m2 each (radius of 1.78 m). In the first field-protecting forest belt, 10 circular counting plots were established, in the second, 10 plots, and in the third, 18 plots. The analysis of undergrowth of forest-forming species revealed that the woody and shrubby vegetation on the test sites is represented by Fraxinus excelsior L., Prunus mahaleb L., Pyrus communis L., Ulmus parvifolia Jacq., Lonicera tatarica L., Quercus robur L., Robinia pseudoacacia L., Acer tataricum L., and Ligustrum vulgare L. It was revealed that the quantitative composition of the first and second field-protecting forest belts is dominated by the undergrowth of Prunus mahaleb L., namely, the first field-protecting forest belt has 72 specimens, and the second has 33 specimens. On the other hand, the third field-protecting forest belt is dominated by the undergrowth of Acer tataricum L. ‒ 46 specimens. A reliable Quercus robur L. juvenile is found in a total illumination of 6250 to 5850 lx, and a questionable one is found in an illumination of 3500 lx. The article substantiates the idea that there is no self-sowing of the sweet cherry oak when the density of the stand is between 208 and 286 trees per hectare (average density). When the tree density increases from 298-327 trees/ha (medium density) to 426 trees/ha (dense tree density), the condition of the self-sown sweet cherry oak is good. In dense stands (783 trees/ha), the vitality of the self-sown seedlings is questionable. The light intensity and density of the stand are interrelated and affect the vitality of the self-sown seedlings of all tree and shrub species in the study areas, while soil moisture and leaf litter mass have a greater impact on seed germination. In all three field-protecting forest belts, there is an accumulation of moisture compared to the control (open space), which is retained by the roots of the tree and shrub vegetation. However, there is not enough moisture in the soil of the field-protecting forest belts for successful self-sowing.