Conservation of nitrogen increases with precipitation across a major grassland gradient in the Central Great Plains of North America

Rebecca L. McCulley, Ingrid C. Burke, William K. Lauenroth

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

Regional analyses and biogeochemical models predict that ecosystem N pools and N cycling rates must increase from the semi-arid shortgrass steppe to the sub-humid tallgrass prairie of the Central Great Plains, yet few field data exist to evaluate these predictions. In this paper, we measured rates of net N mineralization, N in above- and belowground primary production, total soil organic matter N pools, soil inorganic N pools and capture in resin bags, decomposition rates, foliar 15N, and N use efficiency (NUE) across a precipitation gradient. We found that net N mineralization did not increase across the gradient, despite more N generally being found in plant production, suggesting higher N uptake, in the wetter areas. NUE of plants increased with precipitation, and δ15N foliar values and resin-captured N in soils decreased, all of which are consistent with the hypothesis that N cycling is tighter at the wet end of the gradient. Litter decomposition appeared to play a role in maintaining this regional N cycling trend: litter decomposed more slowly and released less N at the wet end of the gradient. These results suggest that immobilization of N within the plant-soil system increases from semi-arid shortgrass steppe to sub-humid tallgrass prairie. Despite the fact that N pools increase along a bio-climatic gradient from shortgrass steppe to mixed grass and tallgrass prairie, this element becomes relatively more limiting and is therefore more tightly conserved at the wettest end of the gradient. Similar to findings from forested systems, our results suggest that grassland N cycling becomes more open to N loss with increasing aridity.

Original languageEnglish
Pages (from-to)571-581
Number of pages11
JournalOecologia
Volume159
Issue number3
DOIs
StatePublished - Mar 2009

Bibliographical note

Funding Information:
NSF Long-Term Ecological Research Program’s Shortgrass Steppe (DEB 9632852) and Konza Prairie sites funded the work. We thank: John Blair, Gene Kelly, and Jason Kaye for experimental and analytical advice; Mark Lindquist, Alan Knapp, John Greathouse, Karen Hickman, and the Van Slykes for logistical support; and Brian Ford, Dani-Ella Betz, Gene Kelly, Peter Adler, and Jim Nelson for volunteer field help. The manuscript was improved by the comments of several anonymous reviewers, for which we extend our thanks. The experiments conducted in this study comply with the current laws of the United States of America.

Keywords

  • Grasslands
  • Net nitrogen mineralization
  • Nitrogen pools
  • Nitrogen use efficiency
  • Regional trends

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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