02206nas a2200181 4500008004100000022001400041245012500055210006900180260001200249300001400261490000700275520155200282100001501834700001201849700001601861700001701877856013001894 2005 eng d a0032-086200aRelationships between health of Quercus robur, occurrence of Phytophthora species and site conditions in southern Sweden0 aRelationships between health of Quercus robur occurrence of Phyt c08/2005 a502 - 5110 v543 a

The effect of Phytophthora species, soil chemistry, precipitation and temperature on the vitality of oak was evaluated in 32 oak stands in southern Sweden. In addition, the relationship between the occurrence of Phytophthora species and soil conditions was determined. The results showed that there was a weak association between the presence of P. quercina, the most frequently recovered Phytophthora species in southern Sweden, and the vitality of the oak stands (determined from estimates of crown defoliation of individual trees). The pathogens occurred more frequently in clayey and loamy soils that were less acidic and which had higher base saturation. However, they were found in all but the most acidic soils (pH < 3ยท5). In stands where Phytophthora species were not present, positive correlations between the average crown defoliation and proportion of damaged trees with average summer precipitation and average annual precipitation were found. There were no significant differences in soil chemistry between healthy and declining stands included in this study, and no significant correlations were found between any soil parameter and crown vitality. Based on the results from these 32 oak stands, it is likely that the decline of oaks in southern Sweden can be attributed to several different site-specific factors, such as infection by P. quercina or unusual weather events, which interact with a number of biotic and abiotic factors, leading to oak decline.

1 aJonsson, U1 aJung, T1 aSonesson, K1 aRosengren, U uhttps://forestphytophthora.org/references/relationships-between-health-quercus-robur-occurrence-phytophthora-species-and-site