1B.2 Sensitivity of Soil Respiration to Variability in Temperature and Moisture in a Semi-Arid Grassland

Monday, 1 May 2023: 9:15 AM
Scandinavian Ballroom Salon 4 (Royal Sonesta Minneapolis Downtown )
Praveena Krishnan, NOAA/ARL/ATDD, Oak Ridge, TN; and T. P. Meyers, M. Heuer, and J. Kochendorfer

Soil surface CO2 efflux or soil respiration (Rs) is a key component of the carbon cycle in grassland ecosystems. Understanding and quantifying the response of soil respiration to environmental variables is of critical importance in assessing the impacts of the changing climate on the ecosystem carbon cycle. The impact of wet and dry soil conditions on soil respiration and its sensitivity to temperature is assessed using continuous automated soil chamber measurements of Rs in 2015 over a semi-arid temperate grassland located on the Audubon Research Ranch in south western Arizona, USA (Ameriflux id: US-Aud). This NOAA’s surface budget network (SEBN) site received below-normal precipitation in July–September of 2015, resulting in a soil water deficit during the growing season. When soil water content (SWC) at the 5 cm depth was > 0.08 m3m-3, soil respiration was positively correlated to soil temperature(Ts) at the 2 cm depth. Below this threshold value of SWC, Rs was largely decoupled from Ts, dropping to less than half of its maximum value during wet soil conditions. Similar patterns were exhibited by eddy covariance measurements of nighttime ecosystem respiration. During periods of soil water stress, the sensitivity of Rs to temperature (dRs/dTs) is substantially reduced, resulting in Q10<2. The results indicate that Rs was less influenced by soil temperature during drought conditions at this semi-arid grassland, and have a negative feedback on Rs, mostly above ~18 °C.
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