The effects of acute ..gamma.. irradiation on two models of phytocenoses - natural polyphytic grasslands and freshwater phytoplankton communities developed in artificial cultures - have been studied. A retardation of the successional process and a simplification of community structure was observed. This included a reduction in biomass and degree of complexity. A selection favouring weeds and other species which are usually present in young successional stages was also apparent. To a large extent, the overall effects of ..gamma..-radiation depended upon the degree of ecological stability and maturity. Radiation-induced disturbances seemed to be buffered in advanced successional stages. The model of response to ..gamma..- radiation was similar to that produced by other factors of ecological exploitation or perturbation. Synecological parameters such as diversity, similarity and stability were also studied for acute phytocenoses. Low radiation levels produced some clear stimulation effects, the possible significance of which is discussed.
Hernandez-Bermejo, J E 
- Universidad Politecnica de Madrid (Spain). Departamento de Biologia y Fisiologia Vegetal de la Escuela T.S. de Ingenieros Agronomos