Responses of trace gases to hydrologic pulses in desert floodplains

Tamara K. Harms, Nancy Grimm

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

Pulsed hydrologic inputs interact with antecedent moisture conditions to shape biogeochemical dynamics in many ecosystems, but the outcomes of these interactions remain difficult to predict. Hydrologic pulses may influence biogeochemical activity through several mechanisms: by providing water as a resource, providing limiting nutrients or substrates that fuel particular biogeochemical pathways, or determining redox conditions. Antecedent moisture conditions may modify the relative importance of each of these potential mechanisms, by influencing accumulation of labile carbon and nutrients, the severity of water limitation to biological processes, and longer-term effects on abiotic conditions, including redox. We experimentally applied hydrologic pulses of different sizes (1-cm and 20-cm events) to soils of desert floodplains and assessed responses of trace gases (CO2, CH4, NO, and N2O) in dry and monsoon seasons to test these mechanisms. Size of the hydrologic pulse strongly interacted with antecedent soil-moisture conditions to determine emissions of some trace gases. Following dry antecedent conditions, water addition stimulated emissions of CO2, CH4, and NO, but not N2O, and larger experimental pulses resulted in larger fluxes. In the monsoon season, responses to water addition were muted and size of the hydrologic pulse had no effect, except for CH4 emission, which increased in response to the 20-cm event. Seasonal contrasts indicated that antecedent moisture conditions constrain the effects of hydrologic pulses on biogeochemical processes, whereas contrasts among responses of different trace gases demonstrated that mechanisms controlling emissions of particular gases are water limitation (CO2), in situ production of nitrogen substrates (NO), or redox conditions (CH4). Strong and predictable interactive effects of water inputs and antecedent conditions indicate that extended droughts may cause elevated emissions of gaseous C and NO following the return of precipitation, whereas larger floods or longer wet seasons are expected to dampen gaseous fluxes, which may contribute to conserving soil C and nutrients within floodplains.

Original languageEnglish (US)
Article numberG01035
JournalJournal of Geophysical Research: Biogeosciences
Volume117
Issue number1
DOIs
StatePublished - Mar 1 2012

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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