@article {KNZ00796,
	title = {Nitrogen competition in a tallgrass prairie ecosystem exposed to elevated carbon dioxide},
	journal = {Soil Science Society of America Journal},
	volume = {65},
	year = {2001},
	pages = {340 -346},
	abstract = {Because N is a limiting nutrient in tallgrass prairie and most ecosystems, changes in N availability or N cycling could control the long-term response of ecosystems to elevated atmospheric CO2 If more C is sequestered into the soil, then greater microbial demand for N could decrease plant-available soil N. Alterations in N dynamics such as plant uptake, N fixation, nutrient cycling, microbial utilization, and partitioning of N into plant and soil fractions ultimately could affect the capability of ecosystems to sequester C. Our objective was to determine if competition for N between plants and microorganisms changes after 8 yr of elevated CO2 relative to ambient conditions. Treatments (three replications, randomized complete block design) were ambient CO2{\textendash}no chamber (NC), ambient CO2{\textendash}chamber (AC), and 2 {\texttimes} ambient CO2{\textendash}chamber (EC). Several short laboratory incubations assessed whether turnover rates of N in soil would be altered under elevated CO2 Gross transformations of N were not altered significantly under elevated CO2 compared with ambient conditions. To examine plant{\textendash}microbial competition and altered allocation patterns of N under elevated CO2, 15NH4{\textendash}N was added to 25-cm-diam. polyvinyl chloride (PVC) cores (15-cm depth) in the field, which were destructively sampled after ≈5 mo. Microbial biomass contained ≈75\% of the total 15N that occurred in the soil organic matter (SOM) and, thus, appeared to be a significant regulator of plant-available N. The SOM under elevated CO2 contained significantly more (>27\%) 15N compared with ambient CO2 conditions. Though a chamber effect was apparent, greater 15N in the SOM pool and greater percentage 15N SOM/percentage 15N plant suggest greater microbial demand for N under elevated CO2},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.2136/sssaj2001.652340x},
	author = {Williams, M.A. and C. W. Rice and Owensby, C.E.}
}
