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Abstract
Introduction
The constant pressure of rigid climatic, soil and hydrological conditions, the presence of pest foci, forest fires, and significant recreational loads lead to a progressive increase in the stresses of pine stands in the Kherson region. The problems of identifying the patterns of forest fires and clarifying the terms of the fire season and the fire hazard period are of great significance now.
The purpose of the research was to determine the main causes and preconditions for the occurrence of forest fires in planted forest stands in the Low Dnieper sands and to identify the most dangerous forest areas in the Kherson region.
Materials and methods
The studying and analyzing results of long-term research of fire science topics developed in Steppe Branch of URIFFM provided the basis of the article. The research was carried out in accordance with the basic provisions of forest science. The differences in the gradation of fire hazard classes for forest areas in the territory of the Low Dnieper sands and other plantations were determined. The main causes of fires in the forests on the territory of the Low Dnieper sands were revealed during fifteen years. An analysis of the occurrence of forest fires in different areas of Kherson region has been carried out. The degree of fire damage, the scorch height on the trunk, the resin exuding, the health indicator, the defoliation and dechromation degree, and the presence of pests were used as the criteria of the pine stand health conditions.
Results
According to studies of Y. G. Rudenko and I. M. Tarasenko, a “fire maturity” of pine plantations occurs not simultaneously in the Low Dnieper sands. The “fire maturity” is defined by site conditions, health of the plantations, and the value ??of the complex index of fire danger.
The main causes of fires in the forests on the territory of Low Dnieper sands can include:
- Natural causes (dry climate, long period of high temperatures, lack of rain, the lightning damage of trees);
- Anthropogenic causes (recreation impact, fires caused by auto or railway transport, grass and harvested field fires at the forest boundary, gas-welding operations near a forest, the presence of broken glass bottles in a forest, and incendiary crime).
In 90 % of cases, the main cause of fires in the forests of the Kherson region is a violation of fire safety rules by the population and in 10 % of cases, it is a lightning-strike fire.
Taking into account the peculiarities of the climatic conditions of the region, the classes of fire hazard by weather conditions should be determined using the local scale, which was developed by scientists of the Steppe Branch URIFFM. There is a significant difference between the indicators proposed by the scientists and the indicators of Prof. Nesterov, which do not consider the climatic differences.
The analysis of the emergence of fires in forestry enterprises during 2005–2015 has allowed ascertaining that Kakhovske and Tsyurupinske forestry enterprise had the top positions in terms of the number of fire incidents, with 588 and 644 cases respectively.
The analysis of the health of forest stands affected by the fire, carried out in 2010, showed deterioration in the overall health condition of the stands in sample plots compared to 2007. Studies in 2016 showed health deterioration in the sample plots by categories. Pests also had a significant influence on the stands’ health degradation in the sample plots throughout the research period. The greatest influence of pests was noted for the 4th and 5th health categories of trees.
Conclusions
Determining the most damaged part of the trees after steady or running surface fires, the availability of a body of information about a certain fire and a list of clear criteria for determining the degree of damage allow forecasting the development of forest areas affected by a fire. The pine trees of the 1st and 2nd health categories were most resistant to the surface fires.
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