[Dynamics of regional ecological frangibility under natural hazard stress: a case study in Qingping Town of Sichuan Province, Southwest China].

By using the aerial remote sensing images after May 12, 2008 (the date of catastrophic Wenchuan Earthquake) and the unmanned aircraft vehicle remote sensing images after August 13, 2010 (the date of extraordinary debris flow), and in combining with the land use map (1:10000), topographic map (1:50000), and collected field investigation data of Qingping Town, Mianzhu City of Sichuan Province in 2006, this paper analyzed and evaluated the ecological frangibility of the Town. In the Town, the slightly, lightly, moderately, heavily, and extremely fragile ecological zones after the extraordinary debris flow occupied 1.9%, 7.9%, 18.7%, 23.0%, and 48.5%, respectively, with the area of heavily and extremely fragile ecological zones accounting for 71.5% of the total, being 238.45 km2, i. e., the ecological environment was overall very fragile. Under the impact of the two natural hazards, the ecological frangibility degree of the Town increased obviously. As compared with that before the Earthquake, the area of heavily and extremely fragile ecological zones after the Earthquake increased by 12.4%, and the area of extremely fragile ecological zone was 1.67 times larger. The dynamic evolution of the ecological frangibility of the Town was mainly manifested in the conversion of heavily fragile ecological zone into extremely fragile ecological zone. Complex terrain was the key factor of the ecological frangibility of the Town.