Morphological abnormalities in young trees of Pinus sylvestris L. in the Kyshtym accident zone: radiation and other environmental factors

Studies conducted in areas affected by the Chernobyl and Fukushima nuclear accidents have revealed that ionizing radiation can cause morphological abnormalities in coniferous trees. This study aimed to evaluate morphological abnormalities in the area affected by the Kyshtym disaster, one of the three most severe nuclear accidents in modern human history. This study was conducted in the zone of the East Ural Radioactive Trace (EURT), which was formed as a result of the Kyshtym disaster in 1957. Current annual radiation doses absorbed by Scots pine needles (Pinus sylvestris) in the EURT impact zone (2.69–16.51 mGy/year) were 11.4-fold higher than background levels, while those in the buffer zone (0.56–1.48 mGy/year) were, on average, 1.3-fold higher. Across a gradient of radioactive contamination young Scots pines exhibited varying frequencies of morphological abnormalities due to ionizing radiation exposure, fungal infections (Cronartium pini, Dothistroma septosporum, Lophodermella sulcigena, Melampsora pinitorqua), and damage by artiodactyl animals (Alces alces, Capreolus pygargus) or insect pests (Retinia resinella, Bupalus piniarius, Diprion pini). We distinguished two groups of effects: in the first group morphological abnormalities are formed mainly under the influence of biogenic factors (multi-toppedness, bushy crowns, abnormal shoot shape, bud lesions); chronic irradiation in these cases affects the state of young Scots pines indirectly, stimulating the development of dormant buds. In the second group, most of the observed morphoses can be considered the result of direct radiation action (number, size, and shape of needles, shortened late-forming shoots as a sign of the recovery process). The analysis of the morphoses in young Scots pine trees in the zone of radioactive contamination demonstrated the need to consider the direct and indirect influence of different environmental factors, including radiation, as well as their interaction. Scots pine morphoses studied 65 years after major nuclear accident in South Urals. Most young pine damages were conditioned by biogenic factors. Specific radiation morphoses were three-needle, short, long, and giant brachyblasts. Short shoots were found only in radioactive contamination zone.