Abstract: To assess the changes of soil organic carbon components and its quality in the wetlands  recovered from farmlands is of importance in the study of wetland ecological restoration. In this paper, surface soil samples were collected from the wetlands having been recovered from farmlands for different durations (2, 5, 8, 10, and 20 years) in the Caizi Lake of Anhui, with the total organic carbon (TOC), particulate organic carbon (POC), and mineralbound organic carbon (MOC) concentrations and the organic carbon quality studied. The TOC, POC, and MOC concentrations all increased significantly with recovery duration, and the increase of active organic carbon exemplified by POC took the priority while that of stable organic carbon exemplified by MOC was relatively lagged behind. With increasing recovery duration, the POC/MOC and the stratification ratio (SR) of TOC and POC increased, reflecting the obvious enhancement of organic carbon activity. The increased organic carbon during the recovery duration was mainly the labile POC which was easily degradable, and thus, having less contribution to the stability of surface soil organic carbon pool. The carbon pool management index (CPMI) analysis showed that the soil quality increased with the recovery duration, and it would take 13 years to recover the soil quality to original level. In the ecological restoration of the wetland recovered from farmland, the soil organic carbon content (carbon pool index, CPI) recovered more quickly, while the soil organic carbon quality (carbon pool activity index, AI) recovered more slowly, which would take 7.6 and 22.7 years, respectively.

Key words: Bt cotton, high temperature, Bt protein, nitrogen metabolic physiology.