34 - 37 (depending on the measurement method) %
||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 paragraph & p.1421 left column bottom 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: "Warming by 4°C increased whole-profile soil respiration by 34 to 37%, depending on the measurement method. The response measured from the surface was a 34% increase from 1100 ± 31 g C m^−2 year^−1 to 1450 ± 43 g C m^−2 year^−1 (treatment effect, P < 0.0001 table S2). The response estimated from gas well data was a similar 37% increase from 1300 to 1750 g C m^−2 year^−1." P.1421 left column bottom paragraph: "The observed 34 to 37% increase in soil respiration due to warming is larger than the 9% (ref 21) and 12% (ref 22) average increases in soil respiration calculated in meta-analyses of warming experiments and is larger than most responses from individual warming experiments (table S1). Although [investigators'] large warming response may be a function of [their] soil type or forest ecosystem (ref 21), it is also due in part to warming the whole-soil profile."