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Greenhouse Gas Production and Transport in Desert Soils of the Southwestern United States
Author(s) -
Oerter Erik,
Mills Jennifer V.,
Maurer Gregory E.,
Lammers Laura Nielsen,
Amundson Ronald
Publication year - 2018
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2018gb006035
Subject(s) - soil water , elevation (ballistics) , environmental science , hydrology (agriculture) , atmospheric sciences , geology , soil science , geotechnical engineering , geometry , mathematics
Deserts comprise a large portion of the Earth's land area, yet their role in the fluxes and cycles of greenhouse gases is poorly known and their likely response to climate change largely unexplored. We report a reconnaissance investigation of the concentrations and fluxes of CO 2 , CH 4 , and N 2 O along two elevation (climate) gradients in the southwestern United States. In‐soil concentrations of CO 2 increased with elevation (up to 5,000 ppm). Concentrations of CH 4 declined with depth in all soils (to less than 1 ppm), but the rates of decrease with depth increased with elevation. In contrast, concentrations and depth trends of N 2 O varied erratically. Soils were net CO 2 sources (0 to >1,500 kg CO 2 ·ha −1 ·year −1 ), and net CH 4 sinks (0.2 to >3 kg CH 4· ha −1 ·year −1 ). The small and variable N 2 O fluxes were inconsistent with the trends in soil N δ 15 N values, which decreased by 5‰ to 6‰ over about 1,000 m of elevation. The high soil N δ 15 N values (up to nearly 17‰ at the lowest elevation) indicate that there is a soil N loss mechanism that is highly depleted in 15 N, and gaseous losses—either NH 3 or N 2 O/N 2 —are suspected of driving these values. In summary, there appears to be a strong climate control on both soil CO 2 and CH 4 concentrations and to a lesser degree on calculated fluxes. The soil N trace gas concentrations indicate that deserts can be either small sources or sinks of N 2 O and that there may be significant consumption of arid soil N 2 O.