Dynamic simulation of soil organic carbon pool of wolfberry forest in the secondary saline-alkali land in the arid regions in Jingtai, Gansu ——Take Jingtai electricity-powered irrigation zone as a case study

The dynamics variations of soil carbon pool were simulated using CENTURY modelbased on the soil layer of 0-20 cm in wolfberry forest growing in the typical secondary saline-alkali land in Hongyue Village of Jingtai County, Gansu. The simulation results showed that there were significant changes in total soil organic matter after planting wolfberry in the reclaimed secondary saline-alkali land which increased firstly and then decreased like the inverted “V.” After the reclamation of secondary saline-alkali land, the soil organic carbon of wolfberry forest rapidly increased during seedling growth stage(1st~4th year old) as “carbon sink stage”, then, it declined gradually during mature stage(8th~12th years old) which reached the level of before land reclamation. Carbon pool activity, carbon pool index(CPI) and carbon pool management index (CPMI) also increased firstly and then decreased, which suggested that soil quality firstly improved through planting wolfberry and then gradually declined with wolfberry growth. These variations closely related with the current farmland management and crops cultivation like irrigation, fertilizer. The wolfberry forest possibly converts to weak carbon emission source in the next 20 to 30 years without change of the current farmland conditions. Therefore, it is very important to employ different measures like changing farmland management, increasing organic fertilizer input, adopting scientific irrigation equipments, and replacing the old seedlings, and so on, to improve the quality of wolfberry forest soil, and increase soil carbon reservation, and reduce the greenhouse effects.