S. K. Alavi Panah - Iran Desert Research Center, University of Tehran, Islamic Republic of Iran.
R. Goossens - Department of Regional Geography and Landscape Study, University of Gent, Belgium.

To use remote sensing data effectively, one must understand the spectral characteristics of the particular features under investigations. To study the relationship between soil salinity and soil reflectance, four MultiSpectral Scanners (MSS) and seven Thematic Mappers (TM bands) over the Ardakan playa located on the Central Iranian Desert margins were selected. In this study soil map, soil salinity observations, an interpolated soil salinity map and ۱۳ images in all, including ۷ TM, ۴ MSS and ۲ Normalised Difference Vegetation Indices (NDVI) images were used. After smoothing the imagery using a ۳× ۳ kernel, and delineating the bare soil from vegetated areas, the correlation coefficients between soil salinity (Electrical Conductivity) and related Digital Number (DN) values from TM and MSS bands on different soil types, such as gypsiferons and saline soils, were calculated. The results obtained demonstrate the trend of the correlation coefficients between soil salinity and the related DN values of MSS and TM bands. Based on the results obtained, we may conclude that the presence of gypsum in soil plays a significant role in lowering the correlation coefficients between soil salinity and surface reflectance -further studies are required to draw more general conclusions. From the results obtained we may also conclude that the behavior of band ۶ of TM on gypsiferous soil is completely different from that on saline soil and, therefore, we may generally conclude that Landsat TM imagery with six reflective bands, on the one hand, and the TM thermal band as complementary information to the TM reflective bands, on the other hand, contained some useful information that may play an important role in soil salinity studies and also the detection of gypsiferous soils in desert areas.

Soil salinity, Gypsiferous soil, MSS bands, Soil reflectance, TM bands