Harmful impact of exceptional cold air outbreak in april 1997 on silver fir in Croatia | Harmful impact of exceptional cold air outbreak in april 1997 on silver fir in Croatia

anglais. After a severe outbreak of cold air in mid and late April in 1997, locally occurring damages on twigs and needles of silver fir were recorded in some forests in Croatia. Field examinations in the first half of July 1997 revealed the damages on one-year and older needles while fully developed twigs of current year growth were left intact. Southern and western slopes with fir growing forests rep­ resented typically affected sites. Further laboratory analyses confirmed the field observation that no harmful insect or pathogens were the cause of these damages. Spread of symptoms, expressed more heavily at lower elevations, indicated a prob­ able connection with recent exceptionally cold air outbreak in mid-April. Physiological disturbances caused by potassium deficiency are discussed in the light of specific occurrences of damage symptoms on silver fir trees.

slovène. After a severe outbreak of cold air in mid and late April in 1997, locally occurring damages on twigs and needles of silver fir were recorded in some forests in Croatia. Field examinations in the first half of July 1997 revealed the damages on one-year and older needles while fully developed twigs of current year growth were left intact. Southern and western slopes with fir growing forests rep­ resented typically affected sites. Further laboratory analyses confirmed the field observation that no harmful insect or pathogens were the cause of these damages. Spread of symptoms, expressed more heavily at lower elevations, indicated a prob­ able connection with recent exceptionally cold air outbreak in mid-April. Physiological disturbances caused by potassium deficiency are discussed in the light of specific occurrences of damage symptoms on silver fir trees.