Effects of Chronic Gamma Irradiation on Plant Communities

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Abstract
Three plant communities or assemblages of plants, the vascular plants of an oak-pine forest, the lichens of that forest, and herbs of an old field, were studied after being exposed experimentally to chronic gamma irradiation. Several kinds of changes in the communities resulted. In all 3 communities irradiation reduced community structure toward the lowest strata or growth-forms of the community. Dominant species replaced one another along the gradient of radiation intensity producing population curves similar to those found along natural environmental gradients. Significant changes in productivity occurred. Species-diversity decreased with increased exposure to radiation. In respect to various tests used in the study, increasing community sensitivity to irradiation was in the sequence forest lichens, old-field herbs, forest vascular plants. Radiation effects on communities relate to evolutionary and ecological phenomena of broad interest, including nuclear volume effects on radiation sensitivity, stature and evolutionary level of plants, population processes determining community composition, and relations of communities to succession and natural environmental gradients.