The role of ammonia volatilization in controlling the natural 15 N abundance of a grazed grassland
Citation
Benjamin F Tracy, and R David Evans, The role of ammonia volatilization in controlling the natural 15 N abundance of a grazed grassland: .
Summary
Although the variation in natural 15N abundance in plants and soils is well characterized, mechanisms controlling N isotopic composition of organic matter are still poorly understood. The primary goal of this study was to examine the role of NH3 volatilization from ungulate urine patches in determining 15N abundance in grassland plants and soil in Yellowstone National Park. We additionally used isotopic measurements to explore the pathways that plants in urine patches take up N. Plant, soil, and volatilized NH3d15N were measured on grassland plots for 10 days following the addition of simulated urine. Simulated urine increased 15N of roots and soil and reduced 15N of shoots. Soil enrichment was due to the volatilization of isotopically [...]
Summary
Although the variation in natural 15N abundance in plants and soils is
well characterized, mechanisms controlling N isotopic composition of
organic matter are still poorly understood. The primary goal of this
study was to examine the role of NH3 volatilization from ungulate urine
patches in determining 15N abundance in grassland plants and soil in
Yellowstone National Park. We additionally used isotopic measurements to
explore the pathways that plants in urine patches take up N. Plant,
soil, and volatilized NH3d15N were measured on grassland plots for 10
days following the addition of simulated urine. Simulated urine
increased 15N of roots and soil and reduced 15N of shoots. Soil
enrichment was due to the volatilization of isotopically light NH3.
Acid-trapped NH3d15N increased from -28‰ (day 1) to
-0.3‰ (day 10), and was lighter than the original
urea-N added (1.2‰). A mass balance analysis of
urea-derived N assimilated by plants indicated that most of the N taken
up by plants was in the form of ammonium through roots. However, isotope
data also showed that shoots directly absorbed 15N –
depleted NH3-N that was volatilized from simulated urine patches. These
results indicate that NH3 volatilization from urine patches enriches
grassland soil with 15N and shoots are a sink for volatilized NH3, which
likely leads to accelerated cycling of excreted N back to herbivores.
Published in Biogeochemistry, volume 68, issue 2, on pages 169 - 178, in 2004.
