International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
4.3 NDVI patterns and quantification
The calculated NDVI patterns of 1988-image and 1997-image
are shown in figure 4. The total pixels to the certain NDVI were
curved in figure 5. Obviously, the NDVI of 1988-image is
higher than the NDVI of 1997-image from both figures 4 and 5,
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0. 20 0. 10 0. 00 0. 10 0. 20 0. 30 0. 40 0.50 0.60 0. 70 0.80
NDVI
Figure 5. NDVI curves for images acquired in 1988 and 1997
in three nature reserves (Changqing, Foping, Guanyinshan) in
the southern slope regions of the Qinling Mountains.
particularly at the lower elevation area or along the rivers. From
figure 5, it can be seen that most of the NDVI are located
between 0.45~0.55 for 1988-curve and 0.55~0.65 for 1997-
curve, and the 1988-curve in pink color seems to be shifted by 1
to the left to the 1997-curve in blue color.
For detailed analysis of NDVI change, figure 6 was created to
display the NDVI ranges and the pixels to relevant NDVI value
for each LUC type mapped previously. Figures 6c and 6d are
the enlarged parts of the small-proportion LUCs with few pixels.
Comparing Figures 6a and 6b, “conifer forest” has almost no
change, while *deciduous broadleaf forest" and “mixed conifer
and broadleaf forest" have great changes: shifted NDVI values
and changed shapes of NDVI-pixel curves. From 1988 to 1997,
pixels of "mixed conifer and broadleaf forest" are greatly
reduced and pixels of “deciduous broadleaf forest" increase.
Comparing Figures 6c and 6d, the differences are more obvious
for four LUC curves between 1988-NDVI and 1997-NDVI. The
numbers of pixel of “water”, “rock and bare-land", and
"farmland and settlement" increase, while the pixels of
“bamboo” and “shrub-grass land” decrease. The NDVI values
of bamboo and shrub-grass land are higher, then farmland and
settlement, rock and bare-land, and water in turn.
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NDVI
NDVI
Figure 6. NDVI curves for various LUC types in three nature reserves (Changqing, Foping, Guanyinshan ) in the southern slope of
the Qinling Mountains. a & c. September 15,1988; b & d. September 8,1997. CF--conifer forest; CFDBF--mixed conifer and
broadleaf forest; DBF--deciduous broadleaf forest; SHGR--shrub-grass land; BAM--bamboo; FAS--farmland and settlement; RAB--
rock and bare-land; WAR--water.
S. DISCUSSION
Results of LUC mapping and LUC change detection show that
the forest has a larger changing area, and “deciduous broadleaf
858
forest" has increased and "mixed conifer and broadleaf forest"
decreased. The changes mostly happen near or along the river
valleys and at the southern boundaries where local people are
living. Human activities, such as forest cutting, crop farming,
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