Problems of natural restoration of forest and green spaces of the resort Caucasian Mineral Waters region

In the forests and green spaces of the Caucasian Mineral Waters resort region there are observed successions, leading to a decrease in their ecological potential. We defined the sanitary conditions and productivity of artificial and natural stands, collected data on species composition and abundance of trees in these stands and non-forested areas. We also determined the level of optimum illumination for the development of oak undergrowth.


Introduction
The Caucasian Mineral Waters region is located in the Central part of the North Caucasus. In 1992 the region was given the status of a specially protected ecological and resort region of the Russian Federation, in order to preserve and reproduce the natural resources of the Caucasian Mineral Waters region.
During the afforestation measures of mineral springs supply zones in the 60's and 70's of the last century, forests were established on the area of 9754.5 hectares. 5% of forest crops had unsatisfactory conditions. Stands of introduced species accounted for 24% of the total area of artificial forests -2378.4 hectares [1].
The area of green spaces of the Caucasian Mineral Waters resort cities is not known due to the lack of their accounting.
There are city parks in the resort towns. One of them is given the status of a specially protected natural area of Federal importance -the Kislovodsk National Park, which covers an area of 966 hectares.
In the forests of the region there are intensive successional processes, which affect the overall environmental condition of the resort region by changing the balance of atmospheric carbon deposition by forests and environment specific changes due to the change of tree species. In natural forests there is a change of oak species to hornbeam and beech to ash [1][2][3][4][5][6][7]. In the forests of artificial origin, the focus of successions has not been studied to date.
In order to identify the direction of the successional process in the most valuable region's forest formations, the characteristics of the renewable process under the canopy of English oak natural stands and artificial stands of introduced species were studied.

Methods and Materials
Permanent sample plots (PP) were laid in accordance with the provisions of the Industry standard [8]. On PP we defined indicators of forest stands, their sanitary condition [9,10].
The undergrowth is considered on the grounds of size 4 m2 in quantity and high groups [11] of 25 pcs in PP. Evaluation of the resumption was given according to the established standards [12]. Healthy undergrowth was considered reliable at a height of 0.5 m and above At the same time, the illumination under the forest canopy space and in the open area was measured using a certified universal meter of meteorological parameters ATT-9508 with a light sensor ATA-1591 (Lutron Electronic Enterprise Co.), Ltd., Taiwan.) Objects of research were a natural coppice stands of Quercus robur L., forest crops of Quercus robur L., Quercus rubra L., Pinus pallasiana D. Don, Pinus kochiana Klotzsch ex K. Koch, Juniperus virginiana L., Fraxinus pennsylvanica Marshall, as well as areas partially or completely devoid of woody vegetation with successful development of the oak undergrowth. Sample plots were laid on the territory of the Kislovodsk National Park and Beshtaugorsky and Essentuksky forest districts.

Results and Discussion
All the studied artificial stands have high productivity -class I forest site, with the exception of Juniperus virginiana and Quercus robur (class II) ( The sanitary condition of the stands varies from weakened to severely weakened, with the exception of P. kochiana, which has no signs of weakening. Weakened stands of Q. rubra and P. Under the canopy of all studied pure forest crops, maternal undergrowth, capable of providing natural reproduction of the growing species, is absent. The most common species reaching the values of reliable undergrowth are F. excelsior and A. platanoides. The number of reliable undergrowth of these native species provides a guaranteed restorative succession under the canopy of introduced crops.
The Q. rubra undergrowth in a small amount occurs in almost all the studied PP, except for the F. pennsylvanica stand. In the plantation J. virginiana Q. rubra occurs in a single instance. Considered an invasive species in the Caucasian Mineral Waters region, Q. rubra rarely reaches the size of a reliable undergrowth.
The studied coppice English oak (PP6-PP9) located on the territory of Beshtaugorsky forest district growing in forest-growing conditions of dry oak stand (C1), belong to the IV-V class of forest site. The sanitary condition of the stands varies from the category weakened to severely weakened with an index of 2.1 to 3.7 (Table. 1). The results of reliable undergrowth accounting in these areas showed that the amount of oak does not exceed 500 pcs/ha and can not be considered significant in the process of reforestation. The exception is the amount of reliable undergrowth of oak (1500 PCs/ha) on PP 9, which is also lower than standard, but significantly higher than in other areas.
The study of the forest crops characteristics on PP10 in the territory of Beshtaugorsky forest district showed that, in general, for the English oak stand artificial origin at the age of 70 years retained its Successful development in the oak forest conditions native deciduous tree species are: hornbeam and ash, and also related -C. betulus, F.excelsior, and also accompanying -U. glabra, A. campestre and P. communis. Their total number on all experimental plots corresponds to the norms of successful natural forest restoration.
On oak restoration research in the Caucasian Mineral Waters region, open areas were discovered immediately adjacent to the forest stands, glades with successful Q. robur and Q. petraea regeneration. Sample plots were laid in the Kislovodsk National Park and Essentuksky forest district. The species and quantitative undergrowth characteristics take into account (Table. 2).
In the studied open areas from 3 to 6 units of species composition is oak in the amount of 1400 to 8600 pieces/ha. Ash, elm and maple sycamore are up to 3 units of composition. In the open space, taking into account the small shading of the adjacent walls of the stand, the oak is not inferior in the success of the resumption of ash and other species.

Conclusion
Artificial stands of introduced species of the Caucasian Mineral Waters region possessing high productivity (I b -II class of a forest site) and having a satisfactory sanitary condition, are not provided with own reliable undergrowth. Successful renewal of predominantly F. excelsior under their canopy is the initial stage of regenerative succession of the native breed.
Natural coppice oak forests of the region belong to the IV-V class of forest type and the category of weakened and severely weakened by sanitary conditions. Oak forest crops are more productive -II class of forest site. Under the canopy of natural and artificial oak stands maternal undergrowth is not formed. In the regeneration process in the oak forest conditions the dominant positions are occupied by Carpinus betulus and Fraxinus excelsior, and also related Ulmus glabra, Acer compestre and Pyrus communis.
More successful oak undergrowth develops on the glades at the soil illumination at the level of 10 % of full lightening, where it occupies positions equivalent to ash and elm.
In order to prevent the change of species in the artificial and natural forests of the Caucasian Mineral Waters resort region, timely measures of care for the undergrowth and forest stands should be carried out according to special programs developed for this purpose.