In this paper, Knapp and Seastedt summarize research undertaken to evaluate several processes affecting the productivity of the tallgrass prairie, and document how these processes are mediated by this large detritus component. A number of ecosystems in North America are maintained by fire and other systems such as the taiga forest decline in productivity when fire or grazing is excluded. The authors believe, however, that the tallgrass prairie is unique among the North American biomes because of the strong negative impacts of plant litter production on subsequent ecosystem function. These deleterious effects of plant litter include: a reduction in available light energy to the system; an alteration of the microclimate and physiology of emerging shoots such that carbon dioxide uptake is reduced; a conversion of immediately usable inorganic nitrogen in rainwater to less readily available organic nitrogen in microbial biomass; an inhibition of nitrogen fixation by free-living microbes and blue-green algae as a result of phosphorus and/or light limitation; and a reduction in soil temperatures, which diminishes root productivity, invertebrate activities, and probably microbial activities as well. Fire and grazing therefor become necessary, integral ecosystem processes that maintain productivity of tallgrass prairie by the removal of standing and falling litter.
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