| In this paper,the TM remote sensing image data in 1991,1999 and the CBERS data in 2006 and the land-use data in the corresponding year of Lanzhou South-north hills are been as the data source.Applying of remote sensing technology,image processing technology of geographic information systems, methods of mathematical statistics,the inter-annual changes,change intensity and the spatial distribution rules of vegetation cover in greening projects area of Lanzhou South-north hills are analysized; At the same time we use the landscape pattern analysis technology to analysize the landscape pattern of greening projects area of Lanzhou South-north hills in 2006; Combined with average annual precipitation and annual mean temperature from 1991 to 2006 of Lanzhou and the other relevant society information ,the driving forces of vegetation cover change of Lanzhou South-north hills are analysized .Study shows that:1.From 1991 to 2006,the vegetation cover of greening projects area of Lanzhou South-north hills has a more substantial increase, which from 1991 to 1999 had smaller increase and from 1999 to 2006 had large increase. In 1991, Qilihe projects area had highest vegetation cover ratio, followed by Chengguan projects area, Yongdeng projects area had lowest vegetation cover ratio; In 1999, Qilihe projects area had the highest vegetation cover ratio, followed by Xigu,Chengguan and Gaolan projects area; In 2006,the vegetation cover ratio was highest in Qilihe projects area, followed by Chengguan,Anning,Xigu,Gaolan projects area. From 1991 to 1999, The vegetation cover ratio grew fastest in Xigu projects area, followed by Chengguan,Gaolan,Qilihe projects area. There was slower increase in Yongdeng projects area; From 1999 to 2006, there was rapid increase in Qilihe,Xigu and Yongdeng projects area, followed by Chengguan, Anning and Gaolan projects area.2.In 1991, the low vegetation cover area accounted for 69% and the secondary vegetation cover area accounted for 27.2% of greening projects area of Lanzhou South-north hills; In 1999, the low vegetation cover area accounted for 38% and the moderate vegetation cover area accounted for 58% of greening projects area of Lanzhou South-north hills; In 2006, the low vegetation cover accounted for 0.08%, moderate vegetation cover area accounted for 27.4% and the higher vegetation cover accounted for 60.52%, the highest vegetation cover area accounted for 12% of greening projects area of Lanzhou South-north hills.3.The total vegetation cover of greening projects area of Lanzhou South-north hills developed towards the direction of augment. From 1991 to 1999, the General Change rate of vegetation cover was 8.7% and annual average change rate was 1.1 on area , the General Change rate was 208.7% and annual average change rate was 26.1 on space, the change trends and status index was 0.042.Changes was stable and was at equilibrium state; From 1999 to 2006, the General Change rate of vegetation cover was 111.5% and annual average change rate was 15.9 on area , the General Change rate was 311.5% and annual average change rate was 44.5 on space, the change trends and status index was 0.36.Changes was relatively stableand was at quasi-equilibrium state.4.From 1991 to 2006, the overall pattern of woodland in various elevation had't changed.It was largest at 1700-1900m elevation range, followed by 1500-1700m elevation range.Again followed by the scope of 1900-2100m elevation.There were no woodland distribution at the else elevation scopes.In 1991,the area of woodland were largest at 0 ~ 9°slope scope, followed by 20°~ 29°scope.Again followed by 10°~ 19°and 30°~ 39°scope; In 2006, the area of woodland were largest at 30°~ 39°slope scope, followed by 0°~ 9°scope.Again followed by 20°~ 29°scope. From 1991 to 2006, in 0 ~ 9°slope scope,woodland area decreased, in 20°~ 29°and 30°~ 39°slope scope, the area of woodland has a more substantial increase, particularly there were more obvious changes at 30°~ 39°slope range. From 1991 to 2006, the overall pattern of woodland in various aspect had't changed.The area of woodlands were largest at shadow aspect, followed by semi-shadow aspect. Thirdly was sunny aspect and finally was semi-sunny aspect.5. From 1991 to 2006,The total index,the assembled status level and the synthesized level of Lanzhou South-north hills wasn't high.In 1991, The synthesized level of Chengguan projects area was highest and the total landscape pattern was best; Followed by Anning projects area, the total landscape pattern was better;Again was Qilihe projects area,but the landscape diversity index,landscape evenness index and vegetation cover ratio were all higest in Qilihe projects area.Last were Xigu and Gaolan projects area,the synthesized level was lower and the total landscape pattern was worse.In 2006,the synthesized level of Gaolan projects area was highest and the total landscape pattern was best; Followed by Qilihe and Xigu projects area, the total landscape pattern was better, of which the landscape diversity index and landscape evenness index of Qilihe projects area were highest; Again was Anning projects area; Chengguan projects area's synthesized level was lowest.From 1991 to 2006,it was obvious that the landscape pattern changed in Lanzhou South-north hills.6.The major driving forces of vegetation cover changes in greening projects area of Lanzhou South-north hills are the policies and people's virescence awareness.In which the strong input of governments at all levels have a key role ; Temperature and precipitation have a certain degree of negative impact.
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