Abstract: This study explored effects of medlar planting on contents of total organic carbon (TOC), active organic carbon (AOC), non active organic carbon (NAOC), and carbon pool management index (CPMI) in secondary salinized soil and compared those contents against what in abandoned salinized agricultural land. The result showed that the contents of TOC, AOC, and NAOC increased by 41.6%, 46.5% and 51.1%; 57.1%, 57.9%, and 54.4%; and 24.0% and 33.2%, 47.3%, respectively in the soil depth of 0-100 cm after medlar planting for 4, 7 and 11 years. The largest increases appeared at the soil depths of 0-10 cm and 60-80 cm. Carbon pool activity and carbon pool activity index had a little increase, carbon pool index (CPI) and CPMI were significantly increased after medlar planting in secondary salinized soil. The soil quality was improved effectively. Correlation analysis showed that the soil fertility improvement and the decrease of soil salinization were closely related to TOC, AOC, NAOC and CPI. The four indices could be used as the indicators to reflect the soil quality improvement of secondary salinized soil.

Key words: medlar, secondary salinized soil, active organic carbon, carbon pool management index