Soils of tallgrass prairie are characterized by large accumulations of organic matter and nutrients, high belowground productivity and a large and diverse assemblage of microbes and invertebrates. Turnover of organic matter and soil nutrient transformations affect both storage of carbon and nutrients in soil pools and uptake of nutrients by primary producers. Both above- and belowground plant responses to fire, grazing and drought are intricately linked to soil processes. Understanding the relationships of above- and belowground processes, and the effects of fire, grazing and nutrient additions on these processes, is the central focus of the belowground plot experiments. The belowground plots were established in 1986 in a replicated split-split plot design. Treatments include burning (annually burned or unburned), mowing (annually mowed or unmowed), and fertilization (N only, P only, N+P, or no fertilizer). Questions being addressed in these experiments include:
Will burning, mowing and fertilization change plant species composition? Will changes in plant species composition affect mycorrhizal fungi and soil invertebrate communities?
Does annual burning result in long-term declines in soil organic matter, as predicted by the CENTURY model (Ojima et al. 1990)? Will annual mowing have a similar effect by reducing allocation of carbon to roots and rhizomes?
What are the seasonal and longer-term dynamics of soil microbial biomass under different treatments? How do these dynamics relate to patterns of nutrient availability and plant uptake?
How do reductions in allocation of carbon to belowground pools, resulting from mowing, affect soil invertebrate communities?
The design of the belowground plots allows us to examine in detail the mechanisms responsible for tallgrass prairie responses to fire, grazing and nutrient limitation. Variables measured in the belowground plots include: plant species composition, aboveground plant biomass and nutrients, root and rhizome biomass and nutrients, litter decomposition, soil C and N pools (stable, mineralizable and microbial biomass), soil and soil solution chemistry, mycorrhizal spore densities, and soil invertebrates.
Ojima, D.S., W.J. Parton, D.S. Schimel and C.E. Owensby. 1990. Simulated Impacts of Annual Burning on Prairie Ecosystems. In (S.L/ Collins and L.L. Wallace, eds) Fire In North American Tallgrass Prairies. University of Oklahoma Press, Norman, OK.