CO2 emissions from a forest soil as influenced by amendments of different crop straws: Implications for priming effects

• Crop straw decomposition coefficient increased linearly with the increase of pH.
• Soil CO2 emissions were controlled by soil enzyme activity, DOC, and pH.
• Winter wheat straw amendment showed a positive priming effect on the forest soil.

In this study, the effects of crop straw amendments on CO2 emissions from a forest soil were investigated by using a 22-day incubation experiment. Five types of crop straw (winter wheat, rice, maize, soybean, and peanut) were used in the experiment and the soil without straw added was control (CK). There were three levels (0.6, 1.2, and 2.4 g) for each straw type. Soil CO2 emission rates were measured 1, 2, 4, 6, 8, 11, 15, 18, and 22 days after the crop straw amendments by using an infra-red gas analyzer. Results showed that the basal soil CO2 emission, i.e. soil organic carbon (SOC) mineralization in CK, was significantly (P < 0.01) lower than the CO2 emission from straw-amended soils. Given a specific straw type, soil CO2 emission was significantly and positively correlated with the amount of straw inputs, yielding the coefficient of determination (R2) ranging from 0.9988 (P = 0.022) to 1.0000 (P < 0.001). The decomposition coefficients, i.e. the slopes of the linear function, of winter wheat, rice, maize, soybean, and peanut straws, were 0.275 ± 0.003, 0.593 ± 0.018, 0.895 ± 0.031, 0.890 ± 0.000, and 1.344 ± 0.039 mg g− 1 per gram straw, respectively. Winter wheat straw amendment induced an about 2-fold increase of basal soil CO2 emission, showing a positive net priming effect (PE). Further investigation indicated that a semi-empirical model based on urease activity, DOC content, and pH could explain 94.5% (R2 = 0.945) variations in soil CO2 emissions. This study supports strong vulnerability of SOC in forest in particular under the scenario of changes in land use and agricultural straw management practice.