Tagging Native Grassland Vegetation with Carbon‐14

Techniques using a plastic tent to contain C 1 4 O 2 gas over herbaceous vegetation were effective for applying a tracer to Missouri tallgrass prairie. The grasses incorporated 67 to 41 μCi of C 1 4 /m 2 from a single exposure to 151 μCi of C 1 4 O 2 /m 2 for 6 hr on clipped and unclipped areas, respectively. Regenerated shoots, which had been clipped 6 weeks earlier, possessed 8 times higher specific activity than unclipped shoots (0.134 vs. 0.017 μCi/g of carbon in foliage biomass). The root systems of both areas possessed over 50% and the roots of mature vegetation as much as 85% of the assimilated C 1 4 remaining in the plant biomass 8 weeks after tagging, thus illustrating the tendency for food reserves to accumulate in underground storage organs late in the growing season. Specific activities in the root systems were similar (0.02 vs. 0.016 μCi/b C) for both revegetated and mature areas and were adequate for study of later translocation, transfer to soil, and in situ decomposition of organic material in soil.