Long-term recovery of a longleaf pine (Pinus Palustris Mill) population following seasonal exposures to ionizing radiation

The long-term effects of ionizing radiation on growth of a longleaf pine population were investigated. Height, diameter and annual increment of radial growth were measured for 81 irradiated trees and 34 control trees. Data were analyzed in a two-way ANOVA, with exposure dose (2.1, 0.7, and 0.17kR) as one variable and season of exposure (spring, summer, fall, and winter) as the other variable. Effects of radiation on radial growth were detectable after 20 years. Trees exposed to higher levels of radiation and trees exposed during seasons of greatest cell activity had the greatest reduction in growth. Trees exposed to the highest dose level (2.1kR) were significantly shorter and had smaller diameters than trees exposed to other dose levels. Trees exposed to radiation in the spring, summer or fall had significantly smaller diameters than trees irradiated in the winter or the control group. Radial growth of all irradiated trees (2.1, 0.7, and 0.17kR) was significantly less than the radial growth of the control trees during all time periods analyzed-1970-1975,1975-1980, and 1980-1985.