Dendroclimatic analysis of «Quercus robur» infected with «Fusarium eumartii»

Abstract

The relationship between the growth increments of declining and healthy Quercus robur and monthly rainfall and temperature data was explored in a Q. robur stand situated near Fagarè (Padova) in north-eastern Italy. As part of the same study, Q. robur growth rings were examined for gum deposits associated with Fusarium eumartii, an anamorphic fungus previously found on declining Q. robur individuals from the same area. The growth rings showed that over the period 1961–1994, declining trees had an average growth increment of 2.24 mm, while for healthy trees the increment was 3.57 mm. The mean monthly temperatures recorded between 1961 and 1994 were normal for the Po-Veneto basin. Mean monthly precipitation in March and April, the months in which resumption of vegetative growth occurs in Q. robur, was 100 mm or less in 1961, 1966, 1968, 1969, 1973, 1976, 1982, 1987, 1988, 1993 and 1994. It is precisely during these months that the rainfall needs of Q. robur exceed 100 mm/month, however. The lower growth recorded in those years was therefore to be attributed to drought in the months of March and April. At the same time F. eumartii was always isolated from the growth rings corresponding to the years 1962, 1967, 1969, 1970, 1977, 1983, 1988, 1989 and 1994. Each of these years followed a year characterised by reduced growth. It is concluded that the decline of the Q. robur population occurring at Fagarè may be due to periods of drought acting as an inciting factor to reduce growth, followed one year later by activity of the pathogen F. eumartii and its metabolites, as a contributing factor.