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Fig. 2. The CO2 released in laboratory incubations showed declining rates across time (top graph; bars are standard errors), as well as declining 
13C (the per mil difference between the carbon-13 content of the sample and the Pee Dee belemnite standard; middle graph), and proportion of CO2 derived from C4 sugarcane (bottom graph). The rate of CO2 release was not affected by N addition (either in the field or laboratory), but the rates were higher at 25°C (high temperature) than at 21.5°C (all others). The middle graph also shows the 
13C for a nearby Eucalyptus plantation that was never cropped with sugarcane (providing a pure C3 signal), and a site that was currently in sugarcane land use (providing a C4 endpoint).
