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 th e fitness of young seedlings exposed to environmental stress. Spring f rosts can cause leaf necrosis and seedling mortality in young oak seed lings, and seedling mortality following spring freeze events is a fact or limiting the northern range limits of Quercus gambelii (Nutt.). We examined the relationship between acorn size and seedling survival fol lowing spring freeze by exposing 1-month-old Quercus rubra (L.) seedli ngs 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 t han control mortality, with survival directly related to acorn size. S eedling size at the end of the first growing season was negatively aff ected by frost exposure and positively associated with acorn size. Ove rwintering mortality (<5%) was negatively associated with seedling siz e. 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.