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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #308483
Title: Plant community change mediates the response of foliar d15N to CO2 enrichment in mesic grasslands

Author
item Polley, Herbert
item Derner, Justin
item JACKSON, ROBERT - Duke University
item GILL, RICHARD - Brigham Young University
item PROCTER, ANDREW - Us Environmental Protection Agency (EPA)
item Fay, Philip

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2014
Publication Date: 12/15/2014
Citation: Polley, H.W., Derner, J.D., Jackson, R.B., Gill, R.A., Procter, A.C., Fay, P.A. 2014. Plant community change mediates the response of foliar d15N to CO2 enrichment in mesic grasslands. In: Proceedings of the American Geophysical Union Fall Meeting, Decmeber 15-19, 2014, San Francisco, California. 2014 CDROM.

Interpretive Summary:

Technical Abstract: Rising atmospheric CO2 concentration may change the isotopic signature of plant N by altering plant and microbial processes involved in the N cycle. Isotope fractionation theory and limited experimental evidence indicate that CO2 may increase leaf delta15N by increasing plant community productivity, C input to soil, and, ultimately, microbial mineralization of old, 15N-enriched organic matter. We predicted that foliar delta15N values would increase as a positive function of the CO2 effect on aboveground productivity (ANPP) of two grassland communities, a pasture dominated by a C4 exotic grass and assemblages of native tallgrass prairie species, the latter grown on each of three soils, a clay, sandy loam, and silty clay. Both grasslands are located in Texas, USA and were exposed in separate experiments to a pre-industrial to elevated CO2 gradient for four years. CO2 enrichment did not consistently increase both ANPP and delta15N. Increased CO2 stimulated ANPP of pasture and of prairie assemblages on each of the three soils. However, CO2 increased leaf delta15N only for prairie plants grown on a silty clay soil. CO2 enrichment led to a shift in dominance from a mid-grass (Bouteloua curtipendula) to a tallgrass prairie species (Sorghastrum nutans) that contributed to increased leaf delta15N on the silty clay soil by increasing ANPP and apparently stimulating mineralization of recalcitrant organic matter. By contrast, CO2 enrichment favored a forb species (Solanum dimidiatum) with higher delta15N values than the dominant grass (Bothriochloa ischaemum) in pasture. Results highlight the role of changes in community composition in CO2 effects on grassland delta15N values.