Abstract: The insitu ¹³CO₂ pulse labeling technique was used to trace the translocation and allocation of ¹³C in Pedicularis kansuensissoil system and assess the dynamic changes of photosynthetically fixed carbon in P. kansuens growing in natural meadow, severely degraded alpine meadow (black beach) and artificial grassland established 5 years in the army ranch of Guoluo Prefecture in the Three Rivers Headwaters region. Results showed that, on the day when carbon was labeled, 39%-71% of the ¹³C was assimilated in the three types of grassland, suggesting that the labeling was in high efficiency and had a great allocation difference. On average, 8.6% of carbon was allocated to soil in the three types of grassland, indicating that the carbon was quickly translocated and allocated unevenly in the P. kansuensissoil system. The δ¹³C values declined in shoots and roots and 5%-27% of the assimilated ^13C was transferred to soil pools after labeling 21 days. The amount of fixed ^13C translocated in soil increased significantly five years after the conversion of “black beach” to artificial grassland. While P. kansuensis has a certain ecological significance for maintaining the diversity and stability of the community, it should be eliminated rationally according to the economic utilization of grassland.

Key words: soil aggregates, cotton, straw-returning, soil nutrient