Citation. Ovington, J. D.; Lawrence, D. B. 1964. Strontium 90 in maize field, cattail marsh and oakwood ecosystems. Journal Appl. Ecology 1:175-181.   [1458  CC]

Abstract. Cedar Creek Natural History Area is situated 50 km (30 miles) north of Minneapolis, Minnesota, USA. At Cedar Creek, within an area of less than 2000 ha, there is a wide range of natural vegetation types, some of which were sampled intensively in 1959 as part of a research programme designed to obtain data on the biomass and productivity of terrestrial ecosystems (Ovington, Heitkamp & Lawrence 1963). At that time, Mr. R. E. Frazier of the State of Minnesota Department of Health was recording strontium 90 in the milk and vegetation from four farms in Minnesota and kindly agreed to determine strontium 90 in some of the plant samples collected at Cedar Creek. Surveys of radioactivity have been done mainly on agricultural crops because of concern about human health with the contamination of food supplies through fallout. Relatively little information is available about strontium 90 in wild ecosystems. The strontium 90 values given here for plant material collected at Cedar Creek are based on single counts, in which the radioactivity was counted for long enough to ensure that the standard deviation of the total radioactivity count was about 10% or less. The number of samples for which strontium 90 could be determined was limited by financial considerations. Consequently great care was taken to ensure the samples sent for analysis were as representative as possible. For instance, the tree bole sample was composed of sub-samples at 2 m intervals up the trunks of three trees selected in the composite sample were adjusted according to the distribution of bole weight in the stand. The Cedar Creek studies enable tentative comparisons to be made of the strontium 90 contents of an annual field crop, maize, Zea mays L., and two natural ecosystems dominated by perennials, a marsh of narrow leaved cattail (reedmace), Typha angustifolia L. and an oakwood, chiefly of northern red oak, Quercus rubra var. Borealis Michz. The maize field and adjacent cattail marsh are about a mile from the oakwood and it seems reasonable to suppose that all receive similar amounts of fallout. Although tests of nuclear weapons were suspended in 1958, the fallout rate of strontium 90 was particularly high during the spring of 1959 when the plant sampling began and decreased in the summer.

Keywords. strontium 90, radioactivity, maize field, cattail marsh, oakwood, productivity, biomass, annual field crop