Assessing Restoration Success of Inland Salt Marshes ( Tamarix chinensis ) Using Soil Labile Organic Carbon Fractions and Enzyme Activities

Inland salt marshes have high carbon sequestration capacity but are highly vulnerable to land-use change. Afforestation is a biological assisted restoration strategy to mitigate wetland degradation, significantly impacting soil organic carbon and enzyme activity. However, the mechanisms underlying these effects remain unclear. This study investigated Tamarix chinensis plantations of different stand ages (3, 7, and 11 years) and adjacent secondary bare land (control) to examine the responses of labile organic carbon fractions and soil enzyme activities to stand age. The results showed that soil organic carbon and total nitrogen content gradually increased with stand age, while soil pH and electrical conductivity initially decreased and then increased with stand age. Compared to the control, the early stages of Tamarix chinensis establishment generally enhanced the content of three labile organic carbon fractions. Urease and peroxidase activities exhibited a continuous increase with plantation age. Conversely, sucrase and alkaline phosphatase activities peaked in the 7-year-old plantation and then declined gradually. Redundancy analysis identified electrical conductivity as the main driver of labile organic carbon variation, while both pH and electrical conductivity were key factors influencing enzyme activities. This study provides scientific references for the restoration and sustainable management of inland salt marshes in China.