Differential Effects of Phragmites australis versus Spartina alterniflora Biochar on Salt Marsh Soil Improvement and Carbon Stabilization

Xiaowen Lin¹Ge Song¹Xin Luo¹Jianping Lai¹Weiting Zhang¹Jin-e Liu^1*Jinlou Huang²Shanshan Xu^1*Khan Waqas¹Minnan Sun¹Jing Bi¹

• ¹Nanjing Normal University, Nanjing, China
• ²Chinese Academy of Sciences, Beijing, China

Biochar is an effective strategy for improving the physicochemical properties of coastal salt marsh soil and enhancing its carbon stabilization. In this study, Spartina alterniflora (S. alterniflora) and Phragmites australis (P. australis) were used as biochar materials. Four pyrolysis temperatures (350°C, 450°C, 550°C, 650°C) and three addition amounts (1%, 2%, 3%) were set to explore the effects of the two biochar on the physicochemical properties and carbon components of salt marsh soil. The results showed that both S. alterniflora biochar (SBC) and P. australis biochar (PBC) significantly increased soil pH, cation exchange capacity, and nutrients (SBC: 5.3%-188.6%, PBC: 1.4%-200.9%) content. The addition of biochar at 3% significantly increased soil TN, NH4+, NO3-and AP, thereby effectively enhancing soil nutrient supply capacity. The addition of SBC and PBC changed the composition of soil organic carbon (SOC), significantly increasing the proportion of mineral-associated organic carbon and thereby promoting SOC stability, particularly under high addition amounts and temperatures. These findings suggest that both SBC and PBC hold promise for improving soil carbon stabilization in coastal salt marsh soil. This study provides a valuable approach for the saline-alkali soil remediation in coastal wetlands and offers a potential pathway for the resource utilization of S. alterniflora and P. australis.