We added a 10 mL 1.25 MSrCl2 solution to another sub-sample of
NaOH solution to precipitate the trapped CO2 as SrCO3. The precipitates
were repeatedly rinsed (8–10 times) with DI water until a solution
pH ~ 7. The supernatant was discarded and the precipitates
were dried in an oven at 60 °C. The δ13C analysis was performed on
SrCO3 precipitates (1.5 mg SrCO3 + 3.0 mg V2O5) using an IRMS
(Harris et al., 1997). The original soil, mulch and lime were also analyzed
for δ13C