EFFECTS OF INITIAL CHEMICAL COMPOSITION ON DECOMPOSITION OF ROOTS OF THREE GRASS SPECIES

Grass root production is a major source of C entering Chernozemic soils. The influence of the initial chemical composition of the roots of three grass species on decomposition was studied in a laboratory incubation experiment. Roots of Stipa comata Trin. and Rupr., Stipa spartea Trin. var. curtiseta Hitchc., and Festuca scabrella Torr. were incubated at 28 C for 47 wk. Carbon dioxide production and percent loss of carbohydrate were inversely related to [(C:N) (% lignin)] (% carbohydrate−½). Percent loss of lignin, however, was directly proportional to this factor. This relationship was also found to fit data in the earlier literature. Decomposition rate appeared to be slower in the laboratory in the absence of soil than has been reported for decomposition rates in field soils. The data are discussed with reference to the dynamics of plant residues and organic matter in soil systems. It is postulated that the effect of soil in controlling decomposition may be as great as the effect of the substrate.