2.3. Soil property analyses
Soil total C and N (nitrogen) contents were measured using an elemental analyzer (EA 3000, Euro Vector, Milan, Italy). The pH was measured in a 1:2.5 soil-water ratio with a pH meter (PHS-3C, LEICI, China). The particle size distribution was examined using the hydrometer method (Bouyoucos, 1962). The WHC was measured by placing a 100-cm3cutting ring filled with thoroughly wetted soil for 24 h on another cutting ring filled with corresponding air-dried soil and allowed to drain for 8 h.
Soil MBC content was measured using the chloroform fumigation extraction method (Vance et al., 1987). Briefly, a soil sample was divided into two sets (4 g per set), one set was fumigated with chloroform for 24 h in the dark, and another set was unfumigated. Then the fumigated and unfumigated samples were extracted with 20 ml 0.5 M K2SO4 in a 1:5 ratio. The extracts were filtered through 0.45 μm syringe filter (Siyan Biotechnology, China) and were determined in the form of total organic C using a Lotix combustion TOC analyzer (Teledyne Tekmar, Mason, OH, USA). Soil MBC was calculated from the K2SO4-extractable organic C between the fumigated and unfumigated samples with a conversion factor of 0.45. Total organic C in unfumigated samples represents DOC.