Spss statistical package v 18

The flux in CH₄ emissions data that did not meet the test for normality (Kolmogorov-Smirnov) were transformed to trigonometric or logarithmic functions prior to testing for seasonal and spatial variability using one-way analysis of variance (ANOVA) and Tukey’s HSD test. Data were analysed using the SPSS statistical package (v. 18.0, Chicago, IL, USA).

The soil samples were air-dried and ground to pass through a 100-micron mesh screen. The plant samples were washed with tap water to remove adhering soil, rinsed with de-ionized water, dried at 60 °C for 48 h in an oven, and then ground into fine powder. The soils were digested using HNO₃-H₂O₂ [23 ]. The plants were digested using HNO₃-HClO₄ [24 ]. Samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrophotometry (AAS). Standard reference materials for soils (GBW-07401) and plants (GBW-07602), obtained from the China National Center for Standard Reference Materials, were digested along with the samples and used for the Quality Assurance/Quality Control program. The precision and bias of the chemical analysis were less than 10%. All analyses were performed with the SPSS statistical package (v18.0) (SPSS Inc., Chicago, IL, USA).