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