The issue of pine forest stands health condition and mortality at the scale of one state enterprise (SE "Lymanske Forest Economy"), located in the Northern part of the Steppe zone of Ukraine, is considered.
For the study data from two repeated observations at 8 permanent plots, laid in 2019, in forest stands with varying degrees of mortality and those damaged by fire was used. A re-survey was carried out in 2020. Using the GIS Field-Map, trees were mapped at the permanent plots and their health condition, mortality, and damage were assessed. For the background assessment of pine forests condition, the results of observations at 7 forest monitoring plots (I level) (surveys of 2015 and 2020) were used. The source of climate data was the online resource ClimateCharts.net.
It was found out that over the last 10 years, due to climate change, the temperature in the region increased and the amount of precipitation decreased, which led to the appearance of a dry period in August, which is unfavourable for the growth of pine forests at the limit of their range. Groundwater levels have changed, as evidenced by the drying of Lake Lyman during 2013-2020. Obtained results showed, that the condition of pine stands in the monitoring plots significantly deteriorated compared to 2015. Currently, the condition of pine forests are considered as "weakened" and "severely weakened" (the health condition index (HCI) of living trees varied from 1.53 to 2.70), the average defoliation and mortality of trees have increased significantly. In weakened stands, the proportion of trees with damage increases over time, in particular, due to the colonization of stem insects. Forest fires pose a significant threat to the pure artificial pine forests that predominate in the region. As a result of fires, the condition of the stands deteriorated (HCI 2.49–2.70) and the number of dead trees increased.

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Dynamics of pine stands condition in SE “Lymanske Forest Economy”

Introduction
Large forests play an important role in the steppe zone, especially in the regions most problematic for forest planting. Negative impacts of climate change become worsened as most pine forests are of artificial origin and are single-layer even-age pure stand. One of the largest forest areas in Donetsk Region is the forests in the State Enterprise (SE) “Lymanske Forest Economy” located in the Siversky Donets River basin. The great importance of these forests for the region is reflected in forest management specificities in. Its largest share (72%) is occupied by forests of conservational, scientific, historical and cultural purposes.
The aim of the study was to analyze the main stand characteristics and the condition of the pine stands in SE “Lymanske Forestry”.
Materials and Methods
The pine stands’ characteristics were studied using the data given in the Forest Fund database as of 01.01.2011 and generally accepted methods in forest mensuration. The condition of trees and stands was determined in accordance with the Sanitary Forests Regulations in Ukraine. At that, 18 sample plots (circular and polygonal) were surveyed for detailed assessment of the condition and structure of pine forests on a typological basis in July-August 2019. The Field-Map technology developed by experts from the Institute of Forest Ecosystem Research (Czech Republic) was used for works on sample plots and primary data processing.
Results
In most sites, stands of dominant tree species correspond to their forest types. However, they have a simplified structure. Thus, the share of pure pine stands is 94.2% of the area. The stands of VI, VII and VIII age classes cover the largest areas – 20.4%, 19.6% and 18.4% accordingly. Furthermore, the II productivity class stands occupy the largest area, namely 43.6%. The share of the I productivity class stands is 30.5% and the stands of the III productivity class cover 16.2% of the area. As for the density of stocking, the stands with that index of 0.8 occupy 47.7% of the area, the stands with the index of 0.7 – 24.3% and those with the index of 0.9 – 14.0%. The forest stands have uneven density of stocking.is. At that, the root rot foci are present there. The polygonal test plots were laid in the interspaces; the circular plots were laid, to compare, in damaged and undamaged parts of the stands. The carried out assessment showed that the health of the stands in the control plots was weakened (health condition indices of 2.27–2.87) and that in the damaged plots is severely weakened (health condition indices of 3.13–3.23). In areas damaged by forest fires, trees condition tends to deteriorate with increasing height and perimeter of fire damages.
Conclusions
The ratio of relief types determines a typological structure of the forests of SE “Lymanske Forest Economy”. Fresh and dry infertile pine forest types and fresh fairly infertile oak and pine forest types cover the largest areas in pine terraces. At that, the pine stands with the medium productivity class prevail: the average site index is I,7; the average density of stocking is 0.76. Comparative analysis of the forest inventory data and field studies showed that there is a necessity to specify forest types and define principal species. The health condition of the pine stands is weakened and severely weakened which is brought about by unfavorable conditions for the stands growth, anthropogenic impact (changes in hydrological regime caused, in particular, by the extraction of minerals and water intakes, and forest fires in 2014) and diseases. The worst condition was observed in the areas damaged by fires (health condition index excluding dead-standing tree was 2.49–2.70).
1 Fig., 5 Tables, 9 Refs.

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V. Yu. Yarotsky

Papers

Стан, структура і продуктивність соснових лісів ДП «Лиманське ЛГ»