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Precipitation variability and fire influence the temporal dynamics of soil CO 2 efflux in an arid grassland
Author(s) -
Vargas Rodrigo,
Collins Scott L.,
Thomey Michell L.,
Johnson Jennifer E.,
Brown Renee F.,
Natvig Donald O.,
Friggens Michael T.
Publication year - 2012
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2011.02628.x
Subject(s) - environmental science , grassland , arid , precipitation , ecosystem , growing season , atmospheric sciences , soil respiration , ecology , soil water , soil science , biology , geography , geology , meteorology
Climate models suggest that extreme rainfall events will become more common with increased atmospheric warming. Consequently, changes in the size and frequency of rainfall will influence biophysical drivers that regulate the strength and timing of soil CO 2 efflux – a major source of terrestrial carbon flux. We used a rainfall manipulation experiment during the summer monsoon season ( J uly– S eptember) to vary both the size and frequency of precipitation in an arid grassland 2 years before and 2 years after a lightning‐caused wildfire. Soil CO 2 efflux rates were always higher under increased rainfall event size than under increased rainfall event frequency, or ambient precipitation. Although fire reduced soil CO 2 efflux rates by nearly 70%, the overall responses to rainfall variability were consistent before and after the fire. The overall sensitivity of soil CO 2 efflux to temperature ( Q 10 ) converged to 1.4, but this value differed somewhat among treatments especially before the fire. Changes in rainfall patterns resulted in differences in the periodicity of soil CO 2 efflux with strong signals at 1, 8, and 30 days. Increased rainfall event size enhanced the synchrony between photosynthetically active radiation and soil CO 2 efflux over the growing season before and after fire, suggesting a change in the temporal availability of substrate pools that regulate the temporal dynamics and magnitude of soil CO 2 efflux. We conclude that arid grasslands are capable of rapidly increasing and maintaining high soil CO 2 efflux rates in response to increased rainfall event size more than increased rainfall event frequency both before and after a fire. Therefore, the amount and pattern of multiple rain pulses over the growing season are crucial for understanding CO 2 dynamics in burned and unburned water‐limited ecosystems.