The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
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From 1996 to 2000, the regions in which the vegetation 
coverage increased were sporadic, especially nearby the river. 
And the regions in which the vegetation coverage decreased 
were mainly in the Longyangxia reservoir and the Lijiaxia 
reservoir. All these showed that the vegetation in study area was 
gradually improving, and the main cause of the vegetation 
decrease was the hydropower development, especially annual 
regulating reservoir. Many land use types were converted to 
water and the vegetation coverage decreased. 
Flat NonhNoitbe. 
: Cast SoulfeCifcsiik*uihSo«tfjivv«stWcst Hartimest 
Aspect 
Figure 4 Vegetation increase rate in different slope aspects and 
elevation in study area from 1977 to 1996 
Figure 2 Vegetation coverage change in study area from 1977 to 
1996 
Figure 3 Vegetation coverage change in study area from 1996 to 
2006 
4.2 Vegetation coverage change character and its impact 
factors analysis 
4.2.1 The relationship between vegetation coverage change 
and the altitude and slope 
According to the relationship of aspect and environmental 
factors, aspect could be divided into sunny slope (the southern 
slope, southwest and southeast slope), shade slope (North Slope, 
northeast and northwest slope) and semi-sunny semi-shade 
slope (West Slope and east slope). From 1977 to 1996, as the 
altitude increased, vegetation increase rate first increased then 
declined. Between 1700-3300 meters above sea level, the higher 
the elevation was, the higher the vegetation increase rate was, 
and the increase rate was higher in the flat and shade slope than 
that in the sunny slope. While at an altitude of 3,300 meters 
above, it showed the opposite trend, and the increase rate in 
sunny slope was higher. 
The change trend of vegetation decrease rate was opposite to 
that of the vegetation increase rate, as the altitude increased, 
vegetation decrease rate first rose then declined. Between 
1700-3300 meters above sea level, the higher the altitude was, 
the lower the vegetation decrease rate was. As a whole, all the 
decrease rates were between 0.138-0.275; more than 3,300 
meters above sea level, vegetation decrease rate was 
significantly higher, especially in the shade slope. 
The reason why the 3,300 meters above sea level was a turning 
point for the two change rates is as follows: During this period 
of time, the Longyangxia reservoir was set up and stored water, 
which is located on above 3,300 meters, resulting in the 
decrease of the vegetation increase rate. 
Ftoi Bist 
Aspect 
Figure 5 Vegetation decrease rate in different slope aspects and 
elevation in study area from 1977 to 1996 
From 1996 to 2007, vegetation increase rate was in a higher 
level, as a whole, all values were between 0.4-0.5. Only in the 
sunny slope and flat at above an altitude of 3,300 meters, 
vegetation increase rate was lower, but all still above 0.1. 
Vegetation decrease rate was generally in a lower level, most 
values were within 0.075 and the values in sunny slope at above 
3,300 meters and 2300 meters below were the lowest. The 
human activities on the flat were the strongest, the overall 
vegetation decrease rate was higher, and there was a peak value 
between 2500-2700 meters above the sea level. This is mainly 
due to the higher the elevation was, the less human interference