Soil Ecology Restoration Group

last update October 29, 2000

Effects of elevated CO2 and nitrogen pretreatments on decomposition on tallgrass prairie leaf litter



Standing dead and green foliage litter wascollected in early November 1990 from Andropogon gerardii (C4), Sorghastrum nutans (C4), and Poa pratensis (C3) plants were grown in large open-topped chambers under ambient or twice ambient CO2 and with or without nitrogen fertilization (45 kg N ha-1). The litter was placed in mesh bags on the soil surface of pristine prairie adjacent to the growth treatment plots and allowed to decay under natural conditions. Litter bags were retrieved at fixed intervals and litter was analyzed for mass loss, carbon chemistry, and total Kjeldahl nitrogen and phosphorus. The results indicate that growth treatments had a relatively minor effect on the initial chemical composition of the litter and its subsequent rate of decay or chemical composition. This suggests that a large indirect effect of CO2 on surface litter decomposition in the tallgrass prairie would not occur by way of changes in chemistry of leaf litter. However, there was a large difference in characteristics of leaf litter decomposition among the species. Poa leaf litter had a different initial chemistry and decayed more rapidly than C4 grasses. We conclude that an indirect effect of CO2 on decomposition and nutrient cycling could occur if CO2 induces changes in the relative aboveground biomass of the prairie species.