Influence of the soil moisture on the formation of foci of root rot of woody species in the stands of Elagin Island

   The main pathogens causing rot of growing trees, their prevalence and influence on the condition of the island's plantations have been identified. Significant damage to the plantations is caused by the agaric honey (Agaricomycetes Doweld), which is the cause of weakening, tree desiccation, windthrow and deadwood. The most widespread are: Armillaria gallica – 45 %; Armillaria cepistipes – 19 %; Desarmillaria tabescens – 16 %; Flammulina velutipes and Kuehneromyces mutabilis – 14 % and 6 %, respectively. The percentage of agaric honey cover in the park ranges from 0.4 % – Kuehneromyces mutabilis – to 4.0 % – Armillaria gallica. Phytopathological condition of plantations is assessed as weakened, the average category for all species is 2.45 points. In order to identify the influence of soil moisture on the formation of root rot foci on the territory of Yelagin Island, the study of soil water regime and phytopathological survey was carried out. Water regime of mineral soils of the island has a number of peculiarities: in May and September groundwater level is close to the surface, in June–August it decreases. The drainage norm necessary for growth and development of trees is not provided in all sections, the probability of flooding of the root-inhabited layer of soil on them was 8 %–32 %, only in some sections the groundwater availability is 0% (no flooding of tree roots was observed). There is a double inflow of groundwater into the soil, capillary-suspended moisture from above and capillary-suspended moisture from below. The groundwater filtration coefficient of the upper soil layer is 1.63 m/day and that of the lower layer is 105.71 m/day, which leads to moisture stagnation. A map of waterlogging of tree roots was drawn up based on measurements of soil-soil water levels. Water stagnation and soil overwatering negatively affect the condition of plantations and favour the development of root rot. The probability of pathogen development increases with increasing soil moisture. A map of pathogen foci has been drawn up.

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