 |
| Titel |
High resolution mapping of Normalized Difference Vegetation Indices (NDVI) of biological soil crusts |
| VerfasserIn |
T. Fischer, M. Veste, A. Eisele, O. Bens, W. Spyra, R. F. Hüttl |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064877
|
|
|
|
|
|
| Zusammenfassung |
| Normalized Difference Vegetation Indices (NDVI) are typically determined using satellite or
airborne remote sensing, or field portable spectrometers, which give an averaged signal on
centimetre to meter scale plots. Biological soil crust (BSC) patches may have smaller sizes,
and ecophysiological, hydrological as well as pedological processes may be heterogeneously
distributed within this level of resolution. A ground-based NDVI imaging procedure
using low-cost equipment (Olympus Camedia 5000z digital camera equipped with a
Hoya R72 infrared filter) was developed in this study to fill this gap at the level
of field research, where carrying costly and bulky equipment to remote locations
is often the limiting factor for data collection. A commercially available colour
rendition chart (GretagMacbeth ColorChecker®) with known red (600-700 nm) and
NIR (800-900 nm) reflectances was placed into each scene and used for calibration
purposes on a per-image basis. Generation of NDVI images involved (i) determination
of red and NIR reflectances from the pixel values of the red and NIR channels,
respectively, and (ii) calculation and imaging of the NDVI, where NDVI values of -1 to +1
were mapped to grey values of 0 to 255. The correlation between NDVI values
retrieved from these images and NDVI values determined using conventional field
spectrometry (ASD FieldSpec 3 portable spectroradiometer) was close (r2 =0.91), the 95%
confidence interval amounted to 0.10 NDVI units. The pixel resolution was 0.8 mm
in the field and 0.2 mm in the laboratory, but can still be improved significantly
with closer distance to the crust or with higher camera resolution. Geostatistical
analysis revealed that both spatial variability as well as size of individual objects
characterized by the NDVI increased with crust development. The latter never exceeded
4 mm in the investigated crusts, which points to the necessity of high resolution
imaging for linking remote sensing with ecophysiology. Perspectively, the new
method could be used for field monitoring of both biological soil crusts and vascular
vegetation.
Literature:
Fischer, T., Veste, M., Eisele, A., Bens, O., Spyra, W., Hüttl, R.F. (2012) Small
Scale Spatial Heterogeneity of Normalized Difference Vegetation Indices (NDVI)
and Hot Spots of Photosynthesis in Biological Soil Crusts. Flora (accepted) DOI:
10.1016/j.flora.2012.01.001
Spröte, R., Fischer, T., Veste, M., Raab, T., Wiehe, W., Lange, P., Bens, O., Hüttl, R.F.
(2010): Biological topsoil crusts at early successional stages on Quaternary substrates
dumped by mining in Brandenburg, NE Germany. Géomorphologie: relief, processus,
environnement 4/2010: 359-370 |
|
|
|
|
|
|