Effect of American Beech Trees on the Gamma Radioactivity of Soils

Abstract

AbstractVarious factors that affect the distribution of gamma‐emitting radioisotopes in soils under mature American beech trees (Fagus grandifolia L.) were investigated. Because of its smooth bark and consequent greater amounts of stemflow this species concentrates more fallout radioisotopes in soil near its stem than most other species.Soil near the stems of beech trees contained considerably more fallout and was subjected to greater leaching of natural radioisotopes, to a depth of 30 cm or more, than soil not affected by stemflow water. Depth penetration of fallout and leaching of natural radioisotopes was greater in Dekalb fine sandy loam than in Bennington silt loam.Radioisotope distribution in soil under these trees was also affected by variations of stemflow around the stems, slope gradient, and the quantity and distribution of organic litter on the forest floor. Near two trees that had variable stemflow, the surface soil contained an average of five times more fallout on the high‐stemflow sides of the stems than on the low‐stemflow sides. Under a beech tree growing on a 20% slope, soil on the downslope side of the stem contained more fallout than soil on the upslope side. Organic litter had a much higher content of fallout than of naturally occurring radioisotopes.As a consequence of the greater concentrations of fallout, herbaceous plants, spicebush (Lindera benzoin L.), and American beech saplings growing near the stems of mature beech trees had higher uptakes of these radioisotopes than those growing farther from the stems.