Over the last decades, after prolonged periods of drought and hot airwaves, massive forest drying has occurred in many countries. Studies show that this pathological process is the result not only of unfavorable climatic conditions but also of combining them with harmful biotic factors (mostly insect pests and fungal diseases).n 2016 a team of the Science for Nature Foundation conducted a pilot study of the health of a group of trees in the Rila Mountains. The study uses a combination of classical and innovative methods for assessing tree condition, such as:
– macroscopic analysis (external evaluation);
– microscopic analysis (determination of the species or generic nature of the pest);
– Dandrochronology analysis (extraction of annual ring data);
– capture and mapping with aircraft (to achieve greater precision in the phytosanitary assessment of very tall trees and dense spruce groups);
– creation of a geographic information system.
The results of the study indicate 3 stressful periods in the life of the trees. The first period began in 1913 and ended in 1931. The second period covered the years from 1941 to 1948. The third longest stressed period was after 1985 and with few exceptions continued in 2016. Climate conditions (temperature-relaxation regime) are a major growth factor for the plantation. Average air temperatures in June have the most significant positive impact on the radial growth indices. Undoubtedly the most negative influence is the temperatures for September.
Several types of pathogens are registered in the surveyed plant:
– Dwarf rust Melampsorella caryophyllacearum </ em> causing a droopy broom in the fir tree;
– Root sponge Heterobasidion annosum </ em>. As a result of its development, the roots and stem are rotten to a considerable height;
– Branch Armillaria ostoyae </ em>. Causes white peripheral rot on the roots of the trees;
– Insect pests such as Ips typographus typhoid, Pityokteines curvidens, whose calamities cause massive drying and bumping or blooming of trees by wind or snow.