Comparative Analyses of Carbon Dynamics in Native and Cultivated Ecosystems

Plant productivity, litter decomposition rates, and soil organic matter accumulation for winter wheat and for unbroken tallgrass prairie in Central Missouri were analyzed and compared. As measured in this 3-yr study, annual production of dry matter above- and belowground for the cultivated system averaged slightly higher than that for the natural vegetation burned every 3-4 yr. Prairie was characterized by greater year-to-year fluctuation of productivity, which in some years exceeded productivity of the cultivated system. More litter and structural biomass older than 1 yr occurred in the prairie, reflecting the perennial nature of the root system. Principal pathways of carbon transfer in both ecosystems were modeled, and mean residence time in major storage compartments estimated. Combined CO² losses from above- and belowground litter decay, expressed as a percentage of total soil respiration, were twice as great under wheat as for native prairie. A relatively greater fraction of net primary production was available for synthesis of soil organic matter in native prairie. Under equilibrium conditions, decomposition constants for this compartment, however, were similar. Contrasts in community structure and phenology, seasonal dynamics of litter decay, and levels of soil disturbance are suggested influences affecting transfer and storage characteristics.