Abstract:
Many studies have focused on the effects of different improvement measures for reclaimed lands, but few have evaluated the effect of the different treatments on soil carbon budget in this study, the soil organic carbon (SOC), the plant biomass and soil respiration (SR) were analyzed to evaluate the effect of the different treatments on soil carbon budget. The soil microbial activities and characteristics were determined to further explore the effect mechanism on SR. Two treatments based on incorporating straw were used to improve reclaimed soil in Chongming Dongtan, China. Treatment 1 involved direct incorporation of straw into the soil through tilling, while in Treatment 2, the straw was first composted and then incorporated into the soil through tilling. The results show that after the SOC remediation with Treatment 1, there was an increase of 9.3% while Treatment 2 caused an increase of 9.4% compared with the control. Plant biomass with Treatments 1 and 2 was 3.44 and 1.67 times that of the control, respectively, which indicates a higher carbon input capacity, although soil respiration only increased by 23.5 and 46.4%, respectively. Microbial biomass and ß - glucosidase activity was also higher at the treated sites compared to the control with a tendency of Treatment 2 > Treatment 1 > the control. The microbial community structure at the Treatment 2 site was different than Treatment 1 and the control site. These findings imply that the microbial activities with Treatment 2 were greater than those with Treatment 1, which means a higher rate of carbon metabolism, resulting in increased SR in Treatment 2. Both treatments decreased the soil salinity and bulk density and modified the soil physical structure thereby increasing the plant biomass. Moreover, Treatment 1 with a higher SOC input (plant biomass) and lower SR presented higher carbon sequestration potential. Composted straw incorporation biasing to soil microbial activities and changing the community structure might be an important cause of increased soil respiration in Treatment 2 compared to Treatment 1 (direct incorporation of the straw) and the control.
Keywords:
Soil organic carbon
,
Soil respiration
,
plant biomass
,
Straw returning mode