Mass, Nitrogen, and Phosphorus Dynamics in Foliage and Root Detritus of Tallgrass Prairie

Abstract

Mass nitrogen, and phosphorus of litterfall were measured for 4 yr on annually burned and unburned tallgrass prairie near Manhattan, Kansas. Decomposition and minearilization rates of foliage, flowering stem, and roots were concurrently studied with a series of litterbag and tethered litter experiments. Amounts of nitrogen and phosphorus in living and dead foilage and roots were measured for 2—yr on an annually burned site. Litterfall exhibited seasonal peaks on all sites, with most of the annual litter decompsition occurring in autumn. An average of 52 g°m—2°yr—1 of litter was deposited on the soil of the annually burned watersheds, while 142 g°m—2°—1 was collected on unburned sites. Nitrogen and phosphorus amounts were 0.53 and 0.07 g°m—2°yr—1, respectively, from burned sites and 1.94 and 0.19 g°m—2°yr—1, on unburned sites. Litterfall on unburned sites averaged °35% of aboveground maximum biomass estimates. Litter decay rates varied from a minimum of °10% yr for flowering stems in the canopy to a maximum of °50%/ yr for roots. Foilage and stems act as nitrogen and phosphorus sinks during the first 2 yr of decomposition. Dead roots and rhizomes also act as temporary nitrogen sinks, but unlike foilage, roots appear to minearlize significant amounts of phosphorus during the 1st yr of decay. Root nitrogen to phosphorus ratios may provide a proximate explanation for nitrogen limitation in tallgrass prairies.