Analysis of spatial-temporal change of Qiemo oasis vegetation coverage based on FCD model

Abstract

Using the TM images of Qiemo oasis,Xinjiang Uygur Autonomous Region,obtained in August of 1998,2001,2006 and 2011,the authors built the complex vegetation index VBSI based on FCD model.This index contains vegetation index(NDVI),bare soil index(BI),and shadow index(SI).Furthermore,the vegetation coverage in Qiemo oasis in 1998,2001,2006 and 2011 was calculated separately according to the dimidiate pixel principal and then the vegetation coverage graduation maps were compiled.Based on statistical diagrams and transfer matrices,the authors have drawn some conclusions: ① The overall vegetation coverage area increased 742.62 km2 in the 13 years,and Qiemo oasis was expanding;② The vegetation coverage showed a fluctuation change during the period.Vegetation was restored well from 1998 to 2001 and from 2006 to 2011.The area of recovered vegetation(vegetation transferred to higher coverage) was 2.98 and 1.79 times the area of degraded vegetation(vegetation transferred to lower coverage) from 1998 to 2001 and from 2001 to 2006;Nevertheless,it degraded heavily from 2001 to 2006,the area of degraded vegetation was 435.3 km2,whereas the recovered vegetation area was only 5.41 km2;③ The vegetation coverage change in Qiemo oasis was influenced by such factors as temperature,precipitation in spring and summer,population and anti-desertification projects.