Changes in Landscape Pattern in the Lower Reaches of Tarim River after an Ecological Water Delivery

In the period from 2000 to 2005,the vegetation along the previously dried section of the Tarim River recovered due to the seven separate ecological water deliveries from the Dashkol Reservoir in the lower reaches of the river.In this paper,binary annual vegetation maps involving vegetated and non-vegetated areas were produced based on CBERS/CCD images from 2000 to 2005 using GIS and remote sensing techniques,and landscape indices were computed to analyze the changes in vegetation landscape pattern using the FRAGSTATS software.Results showed that the maximum of vegetation landscape dynamics was 47.83% over the period from 2003 to 2004,while the minimum of it was-1.39% during the period from 2002 to 2003,indicating a vegetation recovery trend during the whole study period.Number of vegetation patches and the landscape shape index also increased,while the contagion index decreased by 36.9.The patch cohesion index became greater than 99 over the whole study period,which implies that landscape fragmentation and dispersion increased,with a higher connectivity of landscape types.Moreover,the average area of vegetation patches increased and the percentage of the recovered vegetation area was negatively related to the distance from the river channel.However,the vegetated landscape occupied still less than 50% of the study area.Remainder of the area was non-vegetated,including takir desert,bare soil and sandy desert,forming the major landscape types in the study area.In buffer zone 1,the minimum fractal dimension of vegetation landscape decreased,the number of patches became a minimum in 2005,and the patch cohesion index increased,which indicated that the vegetation near the river channel was stable and less disturbed by the ecological water delivery,and the patches of vegetation landscape became more concentrated.In buffer zone 1,the largest patch index was always greater than 10%,much higher than those in other buffer zones over the whole study period,suggesting that the vegetation landscape near by the river channel has more ecological dominance.