Effects of acorn size on seedling survival and growth in Quercus rubra following simulated spring freeze

Seed size is an important phenotypic trait commonly associated with the fitness of young seedlings exposed to environmental stress. Spring frosts can cause leaf necrosis and seedling mortality in young oak seedlings, and seedling mortality following spring freeze events is a factor limiting the northern range limits of Quercus gambelii (Nutt.). We examined the relationship between acorn size and seedling survival following spring freeze by exposing 1-month-old Quercus rubra (L.) seedlings from two sites in Massachusetts to -3 degrees C for 8 h. Mortality of 1-month-old frost-exposed seedlings (20-25%) was 10 times higher than control mortality, with survival directly related to acorn size. Seedling size at the end of the first growing season was negatively affected by frost exposure and positively associated with acorn size. Overwintering mortality (<5%) was negatively associated with seedling size. The production of large acorns should confer a selective advantage in habitats susceptible to spring frosts through a positive effect on seedling establishment success under stress.