Decline and physiological response to foliar-deposited salt in Norway spruce genotypes: a comparative analysis

Severe spruce decline in Denmark at the end of the 1980s led to investigations of the physiology and genetics of the decline and the importance of sea salt deposition. Narrow-sense heritability of health in a progeny trial with 8-year-old Norway spruce families (Picea abies (L.) Karst.) was 0.58. Broad-sense heritability in a seed orchard with clones from ortets of southeastern European origin was 0.53. The health of the ortets correlated with family and clone health. Health of families and clones were not correlated. The health of three spruce provenances in the progeny trial varied from 6.3 to 7.7 on a 0-9 scale. Salt stress responses of 12 two-year-old open-ollinated families from the above clones were investigated after dipping branches into different salt solutions. Photosynthesis and transpiration decreased with increasing salt deposition, respiration increased, and water use efficiency increased initially and decreased later. Correlations between field health and physiological salt responses suggested that airborne salt predisposes to spruce decline rather than triggers it. Health of Norway spruce is unlikely to be improved by salt-resistance selection in the laboratory but may be improved by low transpiration and high water use efficiency selection. Visible injuries were primarily determined by the amount of salt taken up.