ELEVATED ATMOSPHERIC [CO2] PROMOTES FROST DAMAGE IN EVERGREEN TREE SEEDLINGS

Growth under elevated [CO2] promoted spring frost damage in field grow n seedlings of snow gum (Eucalyptus pauciflora Sieb, ex Spreng,), one of the most frost tolerant of eucalypts, Freezing began in the leaf mi dvein, consistent with it being a major site of frost damage under fie ld conditions. The average ice nucleation temperature was higher in le aves grown under elevated [CO2] (- 5.7 degrees C versus - 4.3 degrees C), consistent with the greater incidence of frost damage in these lea ves (34% versus 68% of leaves damaged). These results have major impli cations for agriculture, forestry and vegetation dynamics, as an incre ase in frost susceptibility may reduce potential gains in productivity from CO2 fertilization and may affect predictions of vegetation chang e based on increasing temperature.