Great Basin Naturalist Memoirs


Larreo tridentata (Sesse Moc. ex DC) Cov. exposed to 14CO2 retained about 20 percent of its 14C after 16 and also after 26 months. In leaves, however, a lower specific activity was present at 26 months than at 16months, and a smaller percentage of 14C in the plant occurred in leaves at 26 months than at 16 months (3 percent vs 10 percent). This indicates some, but little, reuse of carbon from the structural components of the plants. The strong tendency of the species to retain this carbon may be related to a survival mechanism. After 40 months the results were more erratic, with 11 percent of the 14C remaining in plants and only 2 percent of the total remaining in the leaves. The specific activity of14 C in the organic debris fraction obtained with saturated salt flotation of roots after small and fine roots had been physically removed indicated that from 27 to 35 percent of the organic debris had the same specific activity as roots and probably could be considered as roots. This compares with the 45 percent value determined previously by a different technique. The below-ground to above-ground ratio for biomass of these plants was about 2.5:1. The below-ground to above-ground ratio for the 14C was about 0.5 at 16 months, 1.3 at 26 months, and 2.5 at 40 months. The estimates obtained in this study were used to correct our previous data for below-ground biomass. Accordingly, somewhere between 3000 and 5000 kg/ha roots are present in the Rock Valley area. An increase with time of the below-ground to aboveground 14C ratio probably indicates loss of 14C from above-ground parts rather than additional transport to roots.