Range: ±0.3 unitless
||Hicks Pries CE, Castanha C, Porras RC, Torn MS. The whole-soil carbon flux in response to warming. Science. 2017 Mar 31355(6332):1420-1423. doi: 10.1126/science.aal1319. P.1420 right column 3rd paragraphPubMed ID28280251
||P.1420 right column 2nd paragraph: "[Investigators] warmed soils 4° ± 0.75°C from 10 cm down to 100 cm in the soil profile in three pairs of control and heated plots from November 2013 through February 2016 (Fig. 1 and figs. S1 and S2). [They] used 22 heating rods, each 2.4 m deep, arranged around plots 3 m in diameter (ref 17) with two additional circular heating cables buried 5 cm below the soil surface at radii of 0.5 and 1 m from the plot center. This method imposed 4°C warming while preserving the natural depth gradient and temporal variations in soil temperature. At 5 cm, because of the lack of aboveground heating, the heated plots were on average only 2.4° ± 1.2°C warmer than the control. Soil moisture was slightly decreased in the warmed plots by an average of 1.5 to 3.5% volumetric water content (fig. S3). The soil respiration response, which included microbial and root respiration (but see supplementary text), was determined monthly from seven replicate surface flux measurements per plot and by measuring gas well CO2 concentrations at five depths (15, 30, 50, 70, and 90 cm), from which depth-resolved CO2 production estimates were modeled using Fick’s law."
||P.1420 right column 3rd paragraph: "The mean Q10, the factor by which respiration increases as a result of a 10°C rise in temperature, for the whole-soil profile (measured from the surface) was 2.4 ± 0.3, this Q10 is “apparent” because it describes the emergent response of many processes and is constrained by field conditions. For each sampling date, Q10 was calculated by comparing the respiration and soil temperature (10 cm) in each control and heated plot pair. By directly comparing plot pairs to calculate Q10 instead of fitting a curve to all respiration and temperature data, [investigators] avoided confounding the temperature response with seasonal changes in soil moisture (fig. S4) or plant inputs (ref 4). A Q10 of 2.4 is equivalent to the estimated global median for soil respiration (ref 18) and similar to the mean Q10 of 2.6 for sites spanning the 10° to 20°C temperature range in a global soil respiration database (ref 19)."