Prediction of changes in the health condition of silver birch (Betula pendula Roth)

Abstract

Silver birch (Betula pendula Roth.) forms softwooded broadleaved forests in various natural zones. It is widely used in protective afforestation and urban plantings, it is a pioneer species in the clear-cuts and burnt areas. However, the global warming and anthropogenic pressure promote the susceptibility of silver birch to pests and pathogens. 
 The aim of the research was to assess the trends in the health condition dynamics of silver birch stands depending on forest site conditions and the initial health condition of the trees.
 The research was carried out in the 2015-2019 period in the Silver birch forest stands in Kharkiv region in fresh fairly poor forest site conditions (B2), fresh fairly fertile forest site conditions (C2), and fresh fertile forest site conditions (D2). All the stands were 40–45 years old and had a relative density of stocking 0.7–0.8.
 Health condition class was visually assessed for each tree in July of each year according to “Sanitary rules in the forests of Ukraine”. For each group of sample plots, which corresponded to the main types of forest site conditions, the probability of improvement of health condition, deterioration of health condition, and mortality in 2019 was calculated depending on their health condition in 2015.
 In each year of the studies (2015–2019), the health condition of silver birch stands was the worst in fresh fertile site conditions, which was due to the bacterial wet wood disease. In the fresh fertile forest site conditions, no tree of the 4th class of health condition improved it during the 2015–2019 period, and in fresh fairly fertile forest site conditions 27.7% of silver birch trees improved their health condition. In each type of forest site conditions, the probability of mortality in more weakened silver birch specimens is higher. The probability of silver birch mortality of any class of health condition was the highest in the fresh fertile forest site conditions and the lowest in the fresh fairly poor forest site conditions.