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Title:   Author  item
                                            Sanderson, Mattitem
                                            Johnson, Hollyitem
                                            Liebig, Markitem
                                            Hendrickson, John
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 1/25/2016
                                    Publication  Date: 7/17/2016
                                    Citation: Sanderson, M.A., Johnson, H.A., Liebig, M.A., Hendrickson, J.R. 2016. Isotopic signatures of vegetation change on northern mixed grass prairie. Meeting Abstract. p. 896-897. IN: A. Iwaasa, H.A. Lardner, M. Schellenberg, W. Willms, and K. Larson (eds.). Proceedings of the 10th International Rangeland Congress, Saskatoon, Canada.Interpretive Summary:
                                Technical Abstract: National analyses have shown invasion of northern mixed-grass prairie by nonnative grasses such as Kentucky bluegrass (Poa pratensis L.). Invasion of native prairie by nonnative grasses may compromise ecosystem function and limit potential ecosystem services. Recent data from a long-term (100 year) grazing experiment near Mandan, ND have shown aggressive invasion of native prairie by bluegrass regardless of grazing intensity. We hypothesized that bluegrass invasion should have altered the 13C and 15N levels in the soil (less negative d13C in early years associated with greater native warm-season grass abundance) of the long-term pastures tracking the increased abundance of invasive cool-season grass aboveground. We analyzed archived soils from 1991 and new samples collected in 2014 for 13C and 15N to test the hypothesis. Soil d13C became less negative and d15N increased with increasing stocking rate at both soil depths. Soil C levels in the surface 7.6 cm increased an average of 35% (1.2 g C kg-1) from 1991 to 2014; however, subsurface levels did not change. Soil N in the surface 7.6 cm increased an average of 27% (0.09 g N kg-1) from 1991 to 2014 and subsurface levels did not change. Vegetation in long-term (100 years) pastures changed dramatically during the last 25 years from predominantly C4 grass to an introduced C3 grass. Corresponding changes occurred in soil C and N that may have long-term effects on nutrient cycling.


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