| The tallgrass prairie is one of the major ecosystem types in the contiguous U.S. Fire, grazing, climate, and landscape are the main regulators of primary productivity and soil organic matter dynamics in the prairie. Primary productivity provides the energy inputs for soil organic matter, and the latter provides the nutrients for primary production. Our research studied the soil C and N dynamics, and the microbial ecology of tallgrass prairie as affected by disturbances such as burning, mowing, and N addition.; Research was conducted in the Konza Prairie Natural Area in the Flint Hills of Kansas, from 1989 to 1991 in a field experiment established in 1986. Microbial biomass C and N averaged 165 g C m{dollar}sp{lcub}-2{rcub}{dollar} and 36 g N m{dollar}sp{lcub}-2{rcub},{dollar} respectively, for the surface 30 cm. Accumulation of litter at the surface and greater production of roots near the soil surface resulted in stratification of microbial biomass. Microbial biomass C and N varied temporally, with higher values in early spring and fall and lower values during the summer. Burning increased microbial biomass C in wet years but reduced it in dry years. Mowing tended to decrease microbial biomass by reducing root inputs. Addition of N increased microbial biomass probably by increasing plant biomass inputs. Microbial biomass and activity were mainly regulated by soil moisture. Fungi dominated microbial activity. Microbial populations were not different between treatments.; The active pools of C and N (C{dollar}sb0{dollar} and N{dollar}sb0){dollar} represented 29% and 15% of the total C and N, respectively. A close linkage was determined between C{dollar}sb0{dollar} and N{dollar}sb0,{dollar} and other pools of soil C and N. Burning and N addition tended to increase the size of the active N pool. Responses of the rate of gross N mineralization to the treatments were not consistent.; Plant productivity was increased by burning and N addition. Levels of soil inorganic N are generally low in the prairie, and tended to decrease because of burning or mowing. Decreases in microbial biomass were related to an increase in soil inorganic N and, possibly, to plant N uptake. This would suggest a synchronization between microbial N dynamics and plant N uptake. |
