Hortus Botanicus (Dec 2014)
Soil-borne phytophtoras and woody plants in Saint-Petersburg: new threats of the third millennium
Abstract
In recent years under the conditions of climate change the increased trend towards damages, rot and decline of woody plants at Arboretum of Komarov Botanical Institute RAS has been observed. As a result of 2-year mycological investigation (2012-2013) the wide distribution of phytophthoras has been detected in rhizosphere of many plants and 5 species of Phytophthora have been identified. All of them are soil-borne root-infecting species dangerous to plants growing at Botanical garden BIN: Ph. cinnamomi, Ph. cactorum, besides Ph. citricola, Ph. plurivora and Ph.quercina are firstly recorded in Russia. Ph. quercina is well known in Central and South Europe, but has not been observed yet in the northern latitudes of St. Petersburg. The infection of rhizosphere soil by these dangerous pathogenes has been found in 20 species of trees and shrubs from 15 genera and 13 families. The average year temperature in Saint-Petersburg during the first 13 years of the Third Millennium had ups on 0.5o and reached 6.3o . Temperature of the December, 2006 (3.0o C), July, 2010 (24.4o C) and November, 2013 (4.4o C) appeared to be the highest during the whole period of observations since 1743. The increase in temperature has been accompanied by the enhancement of precipitation. The highest amount of precipitation (863 mm) for the whole period of observations was observed in 2012. The duration of phenological autumn for the same period has enlarged by 12 days, the spring seasons has shortened by 11 days. The duration of winter has shortened by 5 days (from 116 till 111 days), though this is still the longest season of the year (30% ). Autumn is the second season in its longevity (94 days, 26% of the year). There is the tendency to more late beginning of autumnal phenostages of Calendar of Nature and the later beginning of winter. The start of spring also takes place at later dates. The summer phenostages have the tendency to start at more yearly dates. The increasing wetting of air and soil, the weakeaning of frosts, the prolongation of vegetative season, the rise of summer temperatures and the shortening of winter season with the diminishing of soil freezing have been contributing to distribution of Phytophthora species. In conditions of the climate changes the soil-borne phytophthoras constitute the considerable threat to woody plants of city parks and neigbouring forests around Saint-Petersburg.
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