This study was conducted to determine the factors affecting susceptibility of prairie plants to an early summer frost at Cedar Creek Natural History Area, in east-central Minnesota. Data were collected in a previously established experimental field after temperatures fell to 1.3 °C on 20 June 1992, and to 0.3 °c on 21 June 1992. The degree of frost damage to prairie plants was recorded using a scale of frost damage based on visual criteria, and possible causes of variation in frost susceptibility were examined. The degree of frost damage was independent of plant type (grass or forb), life cycle (annual, perennial, or biennial), successional status (early or late), and species origin (native or introduced). No significant correlations were noted between plant height and mean frost damage but there was a significant negative correlation between plant height and maximum frost damage. In addition, there were no significant correlations between frost damage and mean plant biomass allocated to leaves, stems, and roots, mean biomass allocations aboveground and below-ground, and total biomass. However, plants that allocated a greater proportion of biomass to leaves were more severely damaged than plants which allocated less biomass to leaves. The ratio of leaves to total biomass appears to be critical in relation to frosting events because leaves have a high surface area to volume ratio, which allows more surface area to be exposed to cold air masses, thus increasing the freezing rate.


Biology, general