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Input δ 15 N. Gaseous δ 15 N. I. f gas loss ε G. G. Terrestrial δ 15 N (vegetation, soil). Denitrification Zone NO 3 -. f leaching ε L. L. Hydrologic δ 15 N. (Houlton et al., PNAS , 2006 ; Houlton et al., PNAS, 2007; Houlton and Bai , PNAS , 2009
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Input δ15N Gaseous δ15N I fgas loss εG G Terrestrial δ15N (vegetation, soil) Denitrification Zone NO3- fleaching εL L Hydrologic δ15N (Houlton et al., PNAS, 2006; Houlton et al., PNAS, 2007; Houlton and Bai, PNAS, 2009 Bai and Houlton, GBC, 2009)
Observation and modeling Global data Lab and field experiments Houlton and Bai, PNAS, 2009
Hypotheses 1. Inputs? 2. Leaching? 3. Gas loss?
Work at KREW Previous/current work – • d15N of soil and plant matter, Providence (P303) vs. Bull (B203); foliar and soil d15N increased with increasing elevation (Sara Enders’s thesis) Planned/future work – • Stream and deposition – d15N, d18O, Dd17O • Extractable d15N – NH4+, NO3-, DON • Isotope effect expression experiments in soil