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Abstract
Introduction
The harsh environmental and hydro-edaphic conditions of the steppe zone of Ukraine limit the range of forest species; therefore almost all created stands are pure plantations of Scots pine and Crimean pine. The health condition of plantations began to deteriorate sharply; they became massively invaded with insects, the population of which increased each year. During the last decades, the species diversity and the number of pests and forest diseases pathogens are increasing, which evokes a wide drying of the plantations on Low Dnieper sands.
The aim of the research is to determine the present health condition of the pine plantations on the Kinburne and Ivanovska Sand Arenas. The study provides a comparison of the features of the sand arenas and the determination of patterns of adverse factors influence that predispose the depression of pine forests.
Materials and Methods
The objects of the study were the pine plantations of Kinburne and Ivanovska Sand Arenas. The prevailing species were Scots pine and Crimean pine. Young and middle-aged pine stands are dominating in the age structure. The most widespread site class is III–IV. The stand density of the forest stand is mainly 0.6–0.7 and below. The type of forest growth conditions of the studied region is infertile pine site.
On the Kinburne Arena, 25 sample plots were laid out in pure plantations of Scots pine and Crimean pine and 5 sample plots in mixed pine plantations by the method of circular plots.
On the Ivanovska Sand Arena, by the computation course method, 15 sample plots were laid out, 5 of which were in mixed forest stands, and 10 were in pure plantations of Scots pine and Crimean pine. Forest plantations were created according to the scheme of 3 ? 1 m. The age of forest plantations varies from 5 to 63 years.
To evaluate the health condition of the pine forests, a reconnaissance survey of the stands was carried out. On the sample plots, a complete counting of trees by species, thicknesses, and status categories was done. During field work, all manifestations of the negative influence of other biotic and abiotic factors (pests and forest diseases, forest fires, improper forestry activities, etc.) on the forest phytocoenosis were recorded on the sample areas.
Results and Conclusions
The conditions of pine stands on Ivanovska and Kinburne sand arenas have been researched. It was shown that the most of the pine stands of older age groups are characterized by severely weakened health condition. Dynamics of health condition index of pine plantations was simulated. It was described by a power function with the highest rate of approximation (0,519–0,983). The indices of health condition for pine plantations calculated by the models show that depending on species composition, health condition index of Crimean pine in the age range 5–60 years increases from 1 to 2.8, and health condition index of Scotch pine – from 1.1 to 3.5, respectively, on the Kinburn sand arena. These results show significantly better health condition of Crimean pine plantations. A similar trend of health condition index is indicated in Ivanovska sand arena. However, the Crimean pine plantations up to the IV age class are resistant to pests and diseases in comparison with Crimean pine plantations of Kinburn sand arena. The difference of health condition index was ranged from 0.1 to 0.3. The possible reason for the better condition of Crimean pine in Ivanovska sand arena is the lack of Rhizina undulata Fr., which is very common in Kinburn forests. The analysis of the health status of plantations by types of forest site conditions shows the tendency of health condition deterioration as forest site becomes poorer. To improve the health status and to increase the biological stability of pine stands it’s necessary to provide timely thinning and sanitary cuttings for forest stand forming and improvement, as well as to eliminate the residues from logging in accordance with the Rules of fire safety in the forests of Ukraine