The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
469 
SWIR wavelength regions as found in other ecosystems. The 
strong NIR spectral variation is indicative of highly varying leaf 
index (LAI) at the scale of individual plant canopies (Asner et 
a\., 2000). While the SWIR2 (2.1 -2.4pm) region did show some 
variability in the magnitude of reflectance, but the whole 
spectral shapes were highly consistent. 
The NPV spectra show almost constant monotonic-increasing 
reflectance in the visible-NIR region. Several spectral 
absorption features in the SWIR2 (2.1-2.4pm) region are clearly 
apparent. The features near 2.1pm and 2.4pm are associated 
with the presence of cellulose and lignin. 
The spectral characteristics of bare bedrock are also apparent, 
especially the C0 3 absorption feature near 2.3pm. This is due to 
that the most components of bare bedrock in karst ecosystem 
are carbonate, which is mainly composed of limestone (Yuan, 
1993). 
Wavelength (am.) 
ai n 
o u 
lo 
Jlj 
o 
Ù1 
Wavelength (uni) 
NPV 
05 
<D 
o 0.4 
CCS 
t5 o 
•■i— 
CD 
Ltl 0 
Wavelen^h ipm) 
Figure2. Field spectral from the three transects: photosynthetic 
vegetation (PV), non-photosynthetic vegetation (NPV), bare 
bedrock (bedrock). 
3.2. AutoSWIR spectral mixture analysis 
range (0.4-2.5pm), only SWIR2 (2.1-2.4pm), and only tied- 
SWIR2 endmember spectra. Table 1 showed the spectral 
decomposition results for the study area using the four different 
wavelength permutations. 
Wavelength 
permutation 
Land- 
cover 
types 
Study 
area 
Std. 
Dev. 
Field measurements 
PV 
0.436 
0.010 
NPV 
0.272 
0.010 
bedrock 
0.302 
0.020 
SUM 
1.01 
- 
Hyperion full-range 
PV 
0.392 
0.050 
NPV 
0.291 
0.063 
bedrock 
0.377 
0.046 
SUM 
1.06 
- 
Hyperion SWIR2 
PV 
0.157 
0.102 
NPV 
0.312 
0.041 
bedrock 
0.341 
0.053 
SUM 
0.81 
- 
Hyperion tied-SWIR2 
PV 
0.412 
0.060 
NPV 
0.269 
0.033 
bedrock 
0.319 
0.046 
SUM 
1.0 
- 
Table 1. PV, NPV, and bare bedrock cover fractions from 4 
different wavelength permutations using AutoSWIR. 
Spectral unmixing with the full-range (0.4-2.5pm) of Hyperion 
unmixing yielded very close NPV cover fraction to the field 
NPV values. It indicate that full spectral range may provide 
some measure of NPV presence, but it grossly under-estimated 
PV and over-estimate bare bedrock rate. This is likely duo to 
the presence of very bright bare bedrock, which saturates this 
wavelength region and leads to over-estimates of bedrock cover. 
Spectral unmixing with the only SWIR2 (2.1-2.4pm) region of 
the Hyperion data also yielded poor results (Table 1). In karst 
rocky severely degradation region, especially during the 
vegetation senesced period, SWIR2 spectra are dominated by 
bright bare bedrock and NPV, this can lead to a substantial 
under-estimate of PV cover. 
Spectral unmixing with the tied-SWIR region of the Hyperion 
yielded accurate estimates of all three land-cover types (Table 1). 
The field measurements of PV, NPV and bare bedrock fractions 
were well within the statistical uncertainty rang of the 
AutoSWIR results. It was due to the tied-SWIR2 minimized the 
contribution of intra-canopy structural variation to nonlinear 
photon-tissue interactions. These results were consistent with 
the work did by Asner and Lobell (2000), and indicate that the 
tied-SWIR2 (2.1-2.4pm) spectra are a means for estimating the 
dominant land-cover types (PV, NPV and bare bedrock) in karst 
degradation ecosystem. Karst rocky desertification information 
can be accurately extracted from EO-1 Hyperion data. 
4. CONCLUSION 
The Monte Carlo spectral unmixing method, AutoSWIR, 
incorporated both spectral endmember variability and 
uncertainty in the unmixing process. It involved generating a 
large number of endmember (PV, NPV, bedrock) combinations 
for each pixel by randomly selecting spectra from the database 
of field spectra. The performance was evaluated using full 
The research presented here indicates that SWIR2 (2.1-2.4pm) 
spectral region are the main distinctive spectral characteristics 
of photosynthetic vegetation (PV), non-photosynthetic 
vegetation (NPV) and bare bedrock in karst degradation regions. 
It has limitations in using full optical range (0.4-2.5pm) or only 
SWIR2 region of Hyperion to decompose image into PV, NPV