The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
Figure 4. Evaluation map for State indicators in Ordos city Figure 5. Result of Effect indicators analysis in Ordos city 
4.3 Effect Indicators Analysis 
The MODIS/Terra NDVI products from 2001 to 2005 of each 
assessment unit were used to get its range by extremum, which 
is the difference of NDVI, one of effect indicators. 
Meanwhile, land resilience could be characterized by land 
use/land cover evaluation (Chi, et al. 2007). 
Soil erosion index and soil and water conservation index was 
derived from 1:250,000 regional DEM data respectively, 
including slope above 25%, length of river, surface roughness, 
curvature etc. 
Finally we analyze these indicators with PC A and get regional 
state distribution (Figure 5). Among them, contributing value of 
pressure indicator is mainly from soil and water conservation 
index and soil erosion index (Table 4) and 50%-60% area has 
serious soil erosion problem, so, afforestation, strengthen soil 
and water conservation is vital to the regional ecosystem health. 
The state of north-east part of study area is the best, which nears 
the south bank of Yellow River and has sufficient water 
resources, but the soil and water conservation should be 
emphasized to reduce sand input to Yellow River. 
Index 
Weight 
Ratio of grassland degradation 
0.16 
Soil and water conservation index 
0.39 
Difference of NDVI 
0.26 
Land use/land cover evaluation 
0.22 
Soil erosion index 
0.31 
Table 4. Effect indicators weight statistic result 
These response indicators come from regional social economic 
data and generate distribution by CPA (Figure 6). The area ratio 
of natural reserve and afforestation index counts the most part in 
the response indicators (Table 5). The response of north-east 
part is the best and the south-west part is the worst, and 
strengthens enclosure and afforestation could improve the 
response indicators. 
Index 
Weight 
Area ratio of natural reserve 
0.62 
Afforestation index 
0.58 
GDP per capita 
0.37 
Table 5. Response indicators weight statistic result 
N 
9 15 3© 60 5» 
Figure 6. Evaluation map for Response indicators in Ordos city 
Compute a PCA of Pressure, State, Effect and Response 
indicators, multiply each quantifiable value by its weight and 
summarize, then comprehensive value of each assessing unit 
was got by Eq.(2): 
HI = YWi*Ci ( 2 ) 
/=1 
Where HI= comprehensive index of ecosystem health 
Wj= weight of indicator i 
Q= quantitative and dimensionless value of indicators 
The ecosystem health of Ordos region was got by these data