Abstract: It is a precondition of regenerating ecological environment to fully understand the spatial and temporal distribution pattern of vegetation communities.In this paper,a vegetation classification was carried out based on the LANDSAT images in 4 years of 1976,1991,2001 and 2016.The classified results were used to get three landscape indexes,i.e.,the mean patch area (MPA),fractal dimension (F_d) and aggregation index (AI),which were used to analyze the degree and driving forces of vegetation habitat change.Based on the classification for 2001 and 2016,the vegetation distribution in 2031 was predicted by CA-Markov model.The results showed that human activities were the main factors resulting in the change of vegetation communities.The distribution of vegetation communities was changed a lot during the period of 1976-2016,the areas of forests and grasslands were reduced by 91 km² and 169 km² respectively.From 1976 to 2001,the MNAs of forests,shrubberies and grasslands were reduced by 1.22 km²,0.14 km² and 0.16 km²,the AIs of forests,shrubberies and grasslands were decreased by 2.79,0.03 and 8.77,and the Fds of forests,shrubberies and grasslands were increased by 0.013,0.001 and 0.005,respectively.The degree of vegetation community fragmentation was serious.But from 2001 to 2016,the MNAs of forests,shrubberies and grasslands were enlarged by 0 km²,0.13 km² and 0.02 km²,the AIs of forests,shrubberies and grasslands were increased by 2.38,0.21 and 6.55,and the Fds of a forests,shrubberies and grasslands were decreased by 0.005,0.002 and 0.002,respectively.The habitat of vegetation communities was gradually regenerated after 2001.The predicted areas of forests,shrubberies and grasslands in 2031 are 409 km²,486 km² and 550 km² respectively,which nearly equaled to those in 1976.A significant effect of ecological conservation policy had been achieved.

Key words: vegetation community, habitat fragmentation, spatial and temporal distribution pattern, landscape index, the Qilian Mountains