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

Abstract

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.