Response of Soil Respiration and Microbial Biomass to Soil Salinity under Different Water Content in the Coastal Areas of Eastern China

Abstract

Knowledge concerning the response of soil carbon transformation to soil moisture and salinity is essential for saline soil improvements and utilization. An incubation experiment with three moisture levels (50, 75 and 100% of field capacity) and six salinity levels (soil electrical conductivity of 1 : 5 soil suspension as 0.25, 1.01, 2.02, 3.21, 4.92 and 6.17 dS m–1 for S1, S2, S3, S4, S5 and S6 treatment) was conducted with the purpose to investigate the effect of moisture and salinity on soil respiration (SR) and soil microbial biomass carbon (SMBC). Both soil salinity and soil moisture significantly impact SR and SMBC, yet the interaction effect between them was not significant either for SR, or SMBC. SR and SMBC were found to positively correlate with soil moisture but increased first and then decreased along with increasing soil salinity with the maximum values observed at S3 and S2 salinity levels, respectively. It was found significantly higher at S1 or S2 than at S5 or S6 salinity levels. Furthermore, soil moisture was found to be the predominant factor with significant higher effect than soil salinity levels in determining the variation of SR and SMBC. The results suggested that both the active and total soil microbial communities slightly increased when soil salinity was low (0.25 to 1.01 or 2.02 dS m–1), while they were adversely affected by higher salinity (4.92 and 6.17 dS m–1). In addition, the reduction in SR at high salinity and low moisture levels is mostly caused by reduction in SMBC as it was found significantly correlated to SR.