Abstract: As an external disturbance, plateau pika (Ochotona curzoniae) creates trails outside the pika burrows in alpine meadows, which could induce degraded patches. The amalgamation of pika trails and degraded patches can enlarge the area of bared ground, which would seriously influence the integrity of alpine meadows. With the assistance of unmanned aerial vehicle (UAV), we mapped pika trails and degraded patches under various treatments, including mowing frequency and plateau pika density The coverage and connectivity of degraded patches and pika trails were derived and analyzed. The roles of pika trails in grassland degradation were identified. The threshold of plateau pika disturbance on alpine meadows was determined. The results showed that the number of pika trails treated with high pika density increased significantly (P<0.05). The connectivity index of plateau pika trail was positively correlated with the coverage increment of degraded patches (P<0.05). The number of plateau pika burrow entrance was not sensitive to the changes of pika density (P>0.05). With the enlargement of the degraded patches, the number of plateau pika burrows declined (P<0.05) and the connectivity index of plateau pika trails decreased as a parabolic curve. In conclusion, the disturbance of plateau pika could expanse degradation areas by combining the trails with degraded patches. The fragmentation of alpine meadow would be intensified when the proportion of degraded patches reached a threshold of 21%.

Key words: plateau pika, unmanned aerial vehicle, alpine meadow, degraded patch, Heitutan.